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 How to use your
Tatva Practice Book

1
2. Hexagonal Packing
Hexagonal packing is more
efficient. Its coordination
number is 6 and voids in the
packing are smaller than square
packing. If we place another Scan the QR Code in each
layer on square packing then chapter’s theory section to
there are the following
view micro concept videos
related to the chapter, on
SCAN CODE the Vedantu app.
Solid State

Exercise - 2:

2
Solve all types of
1. CsBr crystallizes in a body
centered cubic lattice. The edge
length of unit cell is 436.6 pm.
Given that the atomic mass of
Cs = 133u and Br = 80u, the
exercise questions density of CsBr is:
based on the latest (NEET 2019)
NEET pattern.
(a) 42.5 g/cm3 (b) 0.425 g/cm3
(c) 4.25 g/cm3 (d) 8.5 g/cm3

Answer Key

3
CHAPTER-1: SOLID STATE
For extra exam
Exercise-1: Basic Objective preparation content,
visit the Vedantu app.
Scan the QR code in the You can find previous
Answers Section to view years’ NEET papers with
detailed solutions for all solutions and detailed
exercise questions. analysis.
Founder’s Message
Dear Student,
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Chemistry Team
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6

TABLE OF CONTENTS

s- Block

Theory........................................................................................................................................................ 8

Solved Examples......................................................................................................................................... 20

Exercise - 1 : Basic Objective Questions....................................................................................................... 25

Exercise - 2 : Previous Year Questions......................................................................................................... 35

Exercise - 3 : Achiever’s Section ................................................................................................................. 38

Answer Key .............................................................................................................................................. 110

p-Block (group 13 and 14)

Theory........................................................................................................................................................ 41

Solved Examples......................................................................................................................................... 54

Exercise - 1 : Basic Objective Questions....................................................................................................... 59

Exercise - 2 : Previous Year Questions......................................................................................................... 70

Exercise - 3 : Achiever’s Section ................................................................................................................. 74

Answer Key .............................................................................................................................................. 112

 7

Environmental Chemistry

Theory...................................................................................................................................................... 78

Solved Examples....................................................................................................................................... 88

Exercise - 1 : Basic Objective Questions..................................................................................................... 92

Exercise - 2 : Previous Year Questions....................................................................................................... 103

Exercise - 3 : Achiever’s Section................................................................................................................ 107

Answer Key ............................................................................................................................................. 114

13
s-BLOCK
Chapter 13

s-Block

1. Introduction of Alkali Metals 1.5 Oxidation State

Show +1 oxidation state because by loosing one electron they
(Group 1) get stable noble gas configuration.
The s- block elements are those in which the last electron enters
the outermost s-orbital. As the s-orbital can accommodate only
two electrons, group 1 and group 2 belong to the s-block. Group 1.6 Photoelectric Effect
1 of the periodic table consists of the elements: Li, Na, K, Rb, Cs, The phenomenon of emission of electrons when electromagnetic
and Fr. They are known as the Alkali Metals. These are called rays strikes against them is called photoelectric effect; Alkali metal
alkali metals because they form hydroxides on reaction with water have low I.P. so show photoelectric effect. (Cs and K are used in
which are strongly alkaline in nature. Photoelectric cells).

1.1 Electronic Configuration 2. Physical Properties of Alkali

All the alkali metals have one valence electrons. The loosely held
s-electron in the outermost valence shell of these elements makes
Metals (Group 1)
them the most electropositive metals. They lose the outermost All the alkali metals are silvery-white and soft. Due to the large
electron to give M+ ions. they are not found in free state in nature. size, these elements have low density, which increases down the
group from Li to Cs. However, potassium is lighter than sodium.
The melting and boiling points of the alkali metals are low due to
1.2 Atomic and Ionic Radii the presence of only a single valence electron (weak metallic bond).
The alkali metal atoms have the largest sizes in a particular period The alkali metals and their salts impart characteristic colour to an
of the periodic table. On increase in atomic number, the atom oxidizing flame. This is because the heat from the flame excites the
becomes larger. The monovalent ions M+ are smaller than the outermost orbital electron to a higher energy level. When the
parent atom. The atomic and ionic radii of alkali metals increase excited electron comes back to the ground state, there is emission
on moving down the group. of radiation in the visible region of the spectrum.

Table 13.1: Colour shown by Alkali Metals(Group1)

1.3 Ionization Enthalpy
The ionization enthalpies of the alkali metals are low and decrease
down the group from Li to Cs. This is because the effect of in- Metal Colour Nm
creasing size(Number of shell increases).
Li Crimson Red 670.8
1.4 Hydration Enthalpy
The hydration enthalpies of alkali metal ions decrease with in- Na Golden Yellow 589.2
crease in ionic sizes. Li+ > Na+ > K+ > Rb+ > Cs+. Li+ has maximum
degree of hydration and for this reason lithium salts are mostly
hydrated (LiCl.2H2O) K Violet 766.5

Rb Red Violet 580.0

Cs Blue 455.5

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10 s-BLOCK

Table 13.2 Atomic and Physical Properties of the Alkali Metals

Property Lithium Sodium Potassium Rubidium Caesium Francium

(Li) (Na) (K) (Rb) (Cs) (Fr)
Atomic Number 3 11 19 37 55 87
Atomic Mass (g mol– ) 6.94
1
22.99 39.10 85.47 132.91 (223)
Electronic configuration [He]2s1 [Ne]3s1 [Ar]4s1 [Kr]5s1 [Xe]6s1 [Rn]7s1
Ionization enthalpy 520 496 419 403 376 ~375
/kJ mol –1

Hydration –506 –406 –330 –310 –276 –

enthalpy /kJ mol –1

Metallic radius / pm 152 186 227 248 265 –

Ionic radius 76 102 138 152 167 (180)
m.p. / K 454 371 336 312 302 –
b.p. / K 1615 1156 1032 961 944 –
Density /g cm–3 0.53 0.97 0.86 1.53 1.90 –

3. Chemical Properties 3.3 Reactivity Towards Dihydrogen

The alkali metals are highly reactive due to their large size and low Alkali metals react with hydrogen gas at about 673K to form
ionization enthalpy. The reactivity of these metals increases down hydrides. These hydrides are ionic in nature with high melting
the group points.
(lithium react with hydrogen gas at 1073K)
2M + H2  2M+ H–
3.1 Reactivity Towards Air
The alkali metals tarnish in dry air due to the formation of their
oxides, which in turn react with moisture to form hydroxides. 3.4 Reactivity Towards Halogens
(Lithium react with air and forms mixture of oxide and nitride) The alkali metals readily react vigorously with halogens to form
They burn vigorously in oxygen forming oxides. ionic halides( M+X–). However, lithium halides are covalent in
4 Li + O2  2 Li2 O (oxide) nature.
2 Na + O2 Na2 O2 (peroxide) 2M + X2  2MX
M + O2 MO2 (superoxide)
(M = K, Rb, Cs) 3.5 Reducing Nature
Alkali metals highly reactivity towards air and water, due to this The alkali metals are strong reducing agents, lithium (due to high
reason they are kept in kerosene oil. hydration energy) being the most and sodium the least powerful
Table 13.3 Standard Electrode Potential
3.2 Reactivity Towards Water Li Na K Rb Cs
They react with water to form hydroxide and dihydrogen E° red (V) –3.04 –2.714 –2.925 –2.930 –2.927
2M + 2H2O  2M+ + 2OH– + H2 (M = an lkali metal)
Lithium’s reaction with water is less vigorous than that of sodium The standard electrode potential (E) which measures the reduc-
because of its small size and very high hydration energy. Other ing power represents the overall change as below
metals of the group react explosively with water.
M(s)  M(g)
M(g)  M+(g)+ e–
M(g) + H2O  M+ (aq)

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s-BLOCK 11

3.6 Solutions in Liquid Ammonia ion increases.

The alkali metals dissolve in liquid ammonia giving deep blue On hydrolysis it will give hydroxide, hydrogen peroxide and oxy-
solutions which are conducting in nature. gen gas.
 
2MO2 + 2H2O  2M+ + 2OH– + H2O2 + O2
M   x  y  NH3   M  NH3  x   e  NH3 y 
 The blue colour of the solution is due to the ammoniated
electron which absorbs energy in the visible region of light. 4.2 Hydroxides of Alkali Metals
 The solutions are paramagnetic and on standing slowly lib-  They are obtained by reaction of oxides with water and all
erate hydrogen resulting in the formation of amide. are white crystalline solids.
M (am) + e– + NH3(l)  MNH2(am) +1/2 H2
+
 The alkali metal hydroxides are stronge bases.
In concentrated solution, the blue colour changes to bronze colour  They dissolve freely in water with evolution of much heat
and becomes diamagnetic on account of intense hydration.
 Solubility:
4. General Characteristics of the LiOH < NaOH < KOH < RbOH < CsOH

Compounds of the Alkali 4.3 Halides of Alkali Metals

Metals The alkali metal halides have High melting point, colourless crys-
All the compounds of the alkali metals are generally ionic in na- talline solids.
ture.  Stability order for fluorides: Enthalpies of formation values
for fluorides become less negative as we go down the group
LiF > NaF > KF > RbF > CsF
4.1 Oxides of Alkali Metals  Stability order for chlorides, bromides and
4.1.1. Normal Oxide iodides:Enthalpies of formation values for chlorides, bro-
 All monoxide are ionic in nature mides and iodides become More negative as we go down
 Formed by Li in Excess of air the group.
 Diamagnetic in nature LiX < NaX < KX < RbX < CsX (X = Cl, Br, I)
 Colourless  Stability order for a given metal : Enthalpies of formation
values always becomes less negative from fluoride to io-
 On hydrolysis it will give hydroxide
dide.
M2O + H2O  2M+ + 2OH–
MF > MCl > MBr > MI (M = alkali metal
 Melting and boiling point order for halides:
4.1.2 Peroxides of Alkali Metals fluoride > chloride > bromide > iodide
 Formed by Na in excess of air(in small extant by Li) MF > MCl > MBr > MI (M = alkali metal)
 Diamagnetic in nature  All halides are soluble in water
 Colourless LiF is least soluble in fluorides (due to high LE)
The increasing stability of the peroxide, as the size of the metal CsI is least soluble in iodides (due to less HE)
ion increases.
Other halides of lithium are soluble in ethanol, acetone and
On hydrolysis it will give hydroxide and hydrogen peroxide. ethylacetate
M2O2 + 2H2O  2M++ 2OH– + H2O2

4.1.3 Superoxides of Alkali Metals 4.4 Salts of Oxo-Acids of Alkali Metals

 Formed By K, Rb,Cs in excess of air (in small extant by Na)  Carbonates of alkali metals: Generally thermally stable
(except Li2CO3). The stability increases down the group.
 Yellow or orange in colour
Lithium carbonate is not stable to heat.
 Paramagnetic in nature
Li2CO3 + Heat  Li2O + CO2
The increasing stability of the superoxide, as the size of the metal

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s-Block
12 s-BLOCK
 Bicarbonates of alkali metals Group 1 metals are strongly (ii) It is used o prepare freezing mixture in laboratory [Ice com-
basic, they form solid bicarbonates except Lithium (LiHCO3 mon salt mixture is called freezing mixture and temperature
can exist in solution). goes down to –23°C.]

5. Important Compounds of 5.2.3 Uses

(i) It is used as a common salt
Sodium (ii) It is used for the preparation of Na2O2, NaOH and Na2CO3.
5.1 Sodium Carbonate (Na2CO3·10H2O)
It is also known as a washing soda. 5.3 Sodium Hydroxide (NaOH)
5.1.1 Solvay Process It is also known as a caustic soda.
NH3 + H2O + CO2  NH4HCO3 5.3.1 Preparation
NaCl + NH4HCO3  NaHCO3 + NH4Cl Electrolysis of Brine
150C Na CO + H O + CO
2NaHCO3  NaCl  Na   Cl –
2 3 2 2

5.1.2 Properties At anode: 2Cl–  Cl2 + 2e–

Sodium carbonate is a white crystalline solid which exists as At cathode : Na+  e–  Na
Na2CO3·10H2O. This is also called washing soda. It is soluble in 2Na + 2H2O  2NaOH + H2
water. Sodium hydroxide is generally prepared commercially by the elec-
On heating at 373K Na2CO3·10H2O loses its water of crystallisation trolysis of sodium chloride in Castner-Kellner cell
to form monohydrate. Above 373K, the monohydrate becomes
completely anhydrous and changes to a white powder called soda
-ash
375K  Na CO H O  9H O
Na 2 CO3 10H 2 O  2 3 2 2

375K  Na CO  H O
Na 2 CO 3  H 2 O  2 3 2

Carbonate part of sodium carbonate gets hydrolysed by water to

form an alkaline solution.
CO32–  H 2 O  HCO 3  OH –
5.1.3 Uses
(i) It is used in water softening, laundering and cleaning.
(ii) It is used in the manufacture of glass, soap, borax and caus-
tic soda.
(iii) It is an important laboratory reagent both in qualitative and
quantitative analysis. Fig.13.1: Castner-Kellner cell
5.3.2 Properties
(i) It is white crystalline, deliquescent, highly corrosive solid.
5.2 Sodium Chloride (NaCl)
(ii) It is stable towards heat.
5.2.1 Preparation (iii) It’s aqueous solution is alkaline in nature and soapy in touch.
Prepared from brine containing 25% NaCl. (iv) FeCl3 + 3NaOH  Fe(OH)3 + 3NaCl
5.2.2 Properties NH4Cl + NaOH  NaCl + NH3  + H2O
(i) It is nonhygroscopic but the presence of MgCl2 in common 5.3.3 Uses
salt renders it hygroscopic.
(i) In petroleum refining
(ii) In the purification of bauxite
(iii) For the preparation of pure fats and oils.

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5.4 Sodium Hydrogencarbonate The main points of similarity are:

(i) Lithium and magnesium react slowly with water. Their
(NaHCO3)
oxides and hydroxides are much less soluble and their
It is also known as a Baking soda. hydroxides decompose on heating. Both form a nitride, Li3N
5.4.1 Preparation and Mg3N2, by direct combination with nitrogen.
By absorption of CO2 in Na2 CO3 solution. (ii) The oxides, Li2O and MgO do not combine with excess
oxygen to give superoxide.
Na2CO3 + H2O + CO2  2NaHCO3
(iii) The carbonates of lithium and magnesium decompose eas-
5.4.2 Uses ily on heating to form the oxides and CO2. Solid are not
(i) Sodium hydrogencarbonate is a mild antiseptic for skin in- formed by lithium and magnesium.
fections. (iv) Both LiCl and MgCl2 are soluble in ethanol.
(ii) It is used in fire extinguishers. (v) Both LiCl and MgCl2 are deliquescent and crystallise from
aqueous solution as hydrates, LiCl·2H2O and MgCl2·8H2O.

6. Anomalous Properties of
Lithium 7. Biological Importance of
The anomalous behaviour of lithium is due to the Sodium and Potossium
(i) small size of its atom and ion
(i) Sodium ions are found primarily on the outside of cells,
(ii) High polarising power . As a result, there is increased cova-
being located in blood plasma and in the interstitial fluid
lent character of lithium compounds.
which surrounds the cells.
(ii) These ions participate in the transmission of nerve signals,
6.1 Difference Between Lithium and other in regulating the flow of water across cell
membranes and in the transport of sugars and amino acids
Alkali Metals into cells. Sodium and potassium, although so similar chemi-
(i) Lithium is much harder. Its m.p. and b.p. are higher than the cally, differ quantitatively in their ability to penetrate cell
other alkali metals. membranes, in their transport mechanisms and in their effi-
(ii) Lithium is least reactive but the strongest reducing agent ciency to activate enzymes.
among all the alkali metals. (iii) Thus, potassium ions are the most abundant cations within
(iii) LiCl is deliquescent and crystallises as a hydrate, LiCl·2H2O cell fluids, where they activate many enzymes, participate in
whereas other alkali metal chlorides do not form hydrates. the oxidation of glucose to produce ATP and, with sodium,
(iv) Lithium hydrogencarbonate is not obtained in the solid form are responsible for the transmission of nerve signals.
while all other elements form solid hydrogencarbonates. (iv) There is a very considerable variation in the concentration
(v) Lithium nitrate when heated gives lithium oxide, Li2O, of sodium and potassium ions found on the opposite sides
whereas other alkali metal nitrates decompose to give the of cell membranes. As a typical example, in blood plasma,
corresponding nitrite. sodium is present to the extent of 143 mmolL–1, whereas the
potassium level is only 5 mmolL–1 within the red blood cells.
4LiNO3  2 Li2O + 4NO2 + O2
These concentrations change to 10 mmolL–1 (Na+) and 105
2NaNO3  2 NaNO2 + O2
mmolL–1 (K+). These ionic gradients demonstrate that a dis-
criminatory mechanism, called the sodium-potassium pump,
6.2 Similarities between Lithium and operates across the cell membranes which consumes more
than one-third of the ATP used by a resting animal and
Magnesium about 15 kg per 24 h in a resting human.
The similarity between lithium and magnesium is because of their (v) Sodium ions are found on the outside of cells. These ions
similar sizes: participate in the transmission of nerve signals, in regulat-
atomic radii, Li = 152 pm, Mg = 160 pm; ing the flow of water across cell membranes and in the trans-
ionic radii : Li+ = 76 pm, Mg2+ = 72 pm. port of sugars and amino acids into cells.

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s-Block
14 s-BLOCK

8. Introduction of Alkaline Earth 8.5 Melting and Boiling points

They have low multing point but are higher than corresponding
Metals (Group 2) value of group I.
The elements, beryllium, magnesium, calcium, strontium, barium Reason: They have two valency electrons which may particle in
and radium are in Group-2. All are metals. The oxides of calcium, metallic bonding compared with only one electron in Alkali metal.
strontium and barium were known much earlier than the metals. Consequently group II elements are harder and have higher co-
Later, when the elements were discovered, they were named as hesive energy and, have much higher m.p./b.p. than Alkali metal.
alkaline earth metals. M.P. Be > Ca > Sr > Ba > Mg
B.P. Be > Ba> Ca > Sr > Mg
8.1 Electronic Configuration
Alkaline earth metals have two electrons in the s -orbital of the 8.6 Electropositive and Metallic Character
valence shell. Their general electronic configuration may be rep- Due to low IE they are strong electropositive but not as strong as
resented as [noble gas] ns 2 . Alkaline earth metals compounds AM because of comparatively high IE. The electropositive char-
are ionic in nature. acter increase down the group.
Be < Mg < Ca < Sr < Ba
8.2 Atomic and Ionic Radii
On moving the group, the atomic and ionic radii increase with an 9. Physical Properties
increase in atomic number.
The alkaline earth metals, in general, are silvery white, lustrous
and soft but harder than the alkali metals. Be and Mg appear to be
8.3 Ionization Enthalpies greyish. The melting and boiling points of alkali earth metals are
The alkaline earth metals have low ionization enthalpies due to higher than the corresponding alkali metals due to smaller sizes.
large size of the atoms. Atomic size increases down the group, The electrons in beryllium and magnesium are too strongly bound
their ionization enthalpy decreases The first ionisation enthalp- to get excited by flame and do not impart any colour to the flame
ies of the alkaline earth metals are higher than those of the corre-
sponding Group 1 metals. This is due to their small size as com-
pared to the corresponding alkali metals. It is interesting to note
that the second ionisation enthalpies of the alkaline earth metals
are smaller than alkali metals.
Fig.13.2: Flame Colour

8.4 Hydration Enthalpies

The hydration enthalpies of alkaline earth metal ions are larger 10. Chemical Properties
than those of alkali metal ions.
The alkaline earth metals are less reactive than the alkali metals.
Be2+ > Mg2+ > Ca2+ > Sr2+ > Ba2+ The reactivity of these elements increases on going down the
Compounds of alkaline earth metals are more extensively hydrated group.
than those of alkali metals, e.g., MgCl2 and CaCl2 exist as
MgCl2.6H2O and CaCl2· 6H2O while NaCl and KCl do not form
such hydrates. 10.1 Reactivity Towards Water
Be and Mg are kinetically inert to water because of the formation
of an oxide film on their surface.
Be probably reacts with steam, Mg with hot water, Ca, Sr and Ba
react rapidly with cold water
M + 2H2O  M(OH)2 + H2

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Table 13.4: Atomic and Physical Properties of the Alkaline Earth Metals
Property Beryllium Magnesium Calcium Strontium Barium Radium
(Be) (Mg) (Ca) (Sr) (Ba) (Ra)
Atomic Number 4 12 20 38 56 88
Atomic Mass (g mol– ) 9.01 1
24.31 40.08 87.62 137.33 226.03
Electronic configuration [He]2s 2
[Ne]3s 2
[Ar]4s 2
[Kr]5s 2
[Xe]6s 2
[Rn]7s2
Ionization enthalpy 899 737 590 549 503 509
(I) / kJ mol –1

Ionization enthalpy 1757 1450 1145 1064 965 979

(II) /kJ mol –1

Hydration –2494 –1921 –1577 –1443 –1305 –

enthalpy /kJ mol –1

Metallic radius / pm 111 160 197 215 222 –

Ionic radius 31 72 100 118 135 148
m.p. / K 1560 924 1124 1062 1002 973
b.p. / K 2745 1363 1767 1655 2078 (1973)
Density /g cm–3 1.84 1.74 1.55 2.63 3.59 (5.5)
Standard poteential –1.97 –2.36 –2.84 –2.89 –2.92 –2.92
E° / V for (M / M)4 2+

Occurrence in 2* 2.76** 4.6** 384* 390* 10**

lithosphere

10.2 Reaction with Excess Dioxygen 10.5 Reaction with Dihydrogen

2M + O2  2MO Formed by all group elements All the elements except beryllium combine with hydrogen upon
Ba + O2  BaO2 Ba also forms the peroxide heating to form their hydrides
M + H2  MH2
 BeH2 can be prepared by the reaction of BeCl2 with LiAlH4.
10.3 Reaction with Excess Air
2BeCl2 + LiAlH4  2BeH2 + LiCl + AlCl3
 Powdered beryllium burns brilliantly on ignition in air to
give BeO and Be3N2.
 Magnesium is more electropositive and burns with dazzling 10.6 Reducing Nature
brilliance in air to give MgO and Mg3N2. Their reducing power is less than those of their corresponding
 Calcium, strontium and barium are readily attacked by air to alkali metals. Reducing character increases down the group.
form the oxide and nitride. Table 13.5: Standard Electrode Potential
Be Mg Ca Sr Ba
10.4 Reaction with Halogens E°red (V) –1.97 –2.36 –2.84 –2.89 –2.92
 All the alkaline earth metals combine with halogen at el-
evated temperatures forming their halides.
M + X2  MX2
10.7 Solutions in Liquid Ammonia
Like alkali metals, the alkaline earth metals dissolve in liquid am-
 BeF 2 is best prepared by thermal decomposition of
monia to give deep blue black solutions forming ammoniated ions.
(NH4)2BeF4 BeF2 + 2NH4F
M + (x + y) NH3 (l)  [M (NH3)x]2+ + 2 [e(NH3)y]–
BeCl2 is conveniently made from oxide.
From these solutions, the ammoniates, [M (NH3)6]2+ can be
600800 K BeCl + CO
BeO + C + Cl2  recovered.
 2

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s-Block
16 s-BLOCK

11. General Characteristics of

Compounds of the Alkaline
Earth Metals (a) (b)

11.1 Oxides of Alkaline Earth Metals (c)

Table 13.6: Oxides of Alkaline Earth Metals Fig.13.3: (a) chain structure of BeCl2 in the solid state
(b) chloro-bridged dimer in vapour state
BeO All other oxides (c) linear monomer of BeCl2
BeO - covalent All metals form monoxide MO which
has rock - salt structure.
BeO - amphoteric All oxides are basic (except)
11.4 Salts of Oxo-Acids of Alkaline Earth
Oxides react with water to form sparingly soluble hydroxides. Metals
MO + H2O  M (OH)2 11.4.1 Carbonates
Preparation
11.2 Hydroxides of Alkaline Earth Metals MX(aq) + Na2CO3  MCO3(s) + Na2X, MX is soluble salt of
Hydroxides of Alkaline Earth Metals alkaline earth metals.
Solubility, thermal stability and the basic chracter -  Carbonates of alkaline earth metals are insoluble in water
Mg(OH)2 < Ca(OH)2 < Sr(OH)2 < Ba(OH)2 and can be precipitated by addition of a sodium or ammo-
nium carbonate solution to a solution of a soluble salt of
Beryllium hydroxide is amphoteric in nature -
these metals.
Be(OH)2 + 2OH– [Be (OH)4]2– (Beryllate ion)
 Solubility of carbonates decreases down the group
Be(OH)2 + 2HCl + 2H2O  [Be (OH)4]Cl2
 All the carbonates decompose on heating to give carbon
Less basic and less stable than alkali metal hydroxides.
dioxide and oxide.( Beryllium carbonate is unstable and can
be kept only in the atmosphere of CO2.)
11.3 Halides of Alkaline Earth Metals  The thermal stability of carbonates increases down the group
 Except for beryllium halides, all other halides are ionic in
11.4.2 Sulphates
nature.
 The sulphates of the alkaline earth metals are all white sol-
 Beryllium halides are essentially covalent and soluble in
ids and stable to heat.
organic solvents.
 Sulphates are soluble in water. The solubility decreases
 Beryllium chloride has a chain structure in the solid state,
down the group:
chloro-bridged dimer in vapour state and linear monomer at
temp. > 1200 K BeSO4 > MgSO4 > CaSO4 > SrSO4 > BaSO4
 Hydration extent decreases down the group. 11.4.3 Nitrates
Ex. MgCl2·8H2O, CaCl2·6H2O, SrCl2·6H2O and BaCl2·2H2O Preparation
 Hydrated chlorides, bromides and iodides of Ca, Sr and Ba MCO3(s) + HNO3 (aq)  M (NO3)2(aq) + H2O + CO2
gives off water of crystallization on heating while that of Be
 All the Nitrates decompose on heating to give the oxide like
and Mg are hydrolysed on heating
lithium nitrate.
 Solubility of MF2 < MCl2 (M = alkaline earth metal) due to
2M(NO3)2 + Heat  2MO + 4NO2 + O2
high LE of fluorides
(M = Be, Mg, Ca, Sr, Ba)
 All the Nitrates have Decreasing tendency to form hydrates
on moving down the group

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s-Block
s-BLOCK 17

12. Some Important Compounds (iii) It is used in glass making,

(iv) It is used in tanning industry, for the preparation of bleach-
of Calcium ing powder and for purification of sugar.

12.1 Calcium Oxide (CaO)

It is also known as a Quick lime.
12.3 Calcium Carbonate (CaCO3)
 Calcium carbonate occurs in nature in several forms like
It is prepared on a commercial scale by heating limestone (CaCO3)
limestone, chalk, marble etc.
in a rotary kiln at 1070 - 1270 K.
It can be prepared by-
heat  CaO  CO
CaCO3  2 (i) Passing carbon dioide through slaked lime-
 Callcium Oxide has metling point of 2870 K. Ca(OH)2 + CO2  CaCO3 + H2O
 On exposure to atmosphere, it absorbs moisture and carbon Excess of carbon dioxide should be avoided since this leads
dioxide. to the formation of water soluble calcium
CaO + H2O  Ca(OH)2 hydrogencarbonate.
CaO + CO2  CaCO3 (ii) By he addition of sodium carbonate to calcium chloride-
 It is a basic oxide, combines with acidic oxides at high tem- CaCl2 + Na2CO3  CaCO3 + 2NaCl
perature. It is a white fluffy powder
CaO + SiO2  CaSiO3 It is almost insoluble in water.
6CaO +P4O10  2Ca3(PO4)2 When heated to 1200 K, It decomposes to evolve carbon dioxide.
Uses CaCO3  CaO + CO2
(i) It is an important primary material for manufacturing cement It reacts with dilute acid to liberate carbon dioxide.
(ii) It is used in the manufacture of sodium carbonate from caus- CaCO3 + 2HCl  CaCl2 + H2O + CO2
tic soda. CaCO3 + H2SO4  CaSO4 + H2O + CO2
(iii) It is employed in the purification of sugar Uses:
 It is used as a building material in the form of marble and in
12.2 Calcium Hydroxide (Ca(OH)2) the manufacture of quicklime
 Calcium carbonate along with magnesium carbonate is used
 It is also known as a slaked lime.
as a flux in the extraction of metals such as iron.
 It is prepared by adding water to quick lime, CaO  Specially precipitated CaCO3 is extensively used in the manu-
CaO + H2O  Ca(OH)2 facture of high quality paper.
 The aqueous solution is known as lime water.  It is used as an antacid, mild abrasive in toothpaste, a con-
 When carbon dioxide is passed through lime water it turns stituent of chewing gum, and a filler in cosmetics.
milky due to the formation of calcium carbonate.
Ca(OH)2 + CO2  CaCO3 + H2O
12.4 Calcium Sulphate (CaSO4 ·½ H2O)
 On passing excess of carbon dioxide, the precipitate
dissolves to form calcium hydrogencarbonate.  It is also known as a Plaster of Paris.
CaCO3 + H2O + CO2  Ca(HCO3)2  It is a hemihydrate of calcium sulphate CaSO4·½H2O.
 It is sparingly soluble in water. Suspension of slaked lime in  It is obtained when CaSO4·2H2O, is heated to 393 K.
water is known as milk of lime. 2 (CaSO4·2H2O)  2(CaSO4)·H2O + 3H2O
 Milk of lime reacts with chlorine to form hypochlorite, a  Above 393 K, no water of crystallisation is left and
constituent of bleaching powder. anhydrous calcium sulphate, CaSO4 is formed. This is known
2Ca(OH)2 + 2Cl2  CaCl2 + Ca(OCl)2 + 2H2O as ‘dead burnt plaster
Uses:  It has a remarkable property of setting with water. On mixing
with an adequate quantity of water it forms a plastic mass
(i) It is used in the preparation of mortar, a building material.
that gets into a hard solid in 5 to 15 minutes.
(ii) It is used in white wash

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s-Block
18 s-BLOCK

12.5 Cement (iii) The oxide and hydroxide of beryllium, unlike the hydroxides
 It is also called Portland cement because it resembles with of other elements in the group, are amphoteric in nature.
the natural limestone quarried in the Isle of Portland,
England.
13.1 Similarities Between Beryllium and
 Cement is a product obtained by combining a material rich
in lime, CaO with other material such as clay which contains Aluminium
silica, SiO2 along with the oxides of aluminium, iron and (i) Beryllium is not attacked by acids because of the presence
magnesium. of an oxide film on the surface of the metal. (Like aluminium,)
(ii) Beryllium hydroxide dissolves in excess of alkali to give a
Table 13.7: Percentage of Compound in Cement
beryllate ion, [Be(OH)4] 2– just as aluminium hydroxide
Raw compounds Percentage (iii) The chlorides of both beryllium and aluminium have
CaO 50 - 60% Cl– bridged chloride structure in vapour phase. Both the
SiO2 20 - 25% chlorides are soluble in organic solvents and are strong
Lewis acids.
Al2O3 5 - 10%
(iv) Beryllium and aluminium ions have strong tendency to form
MgO 2-3%
complexes, BeF4 2–, AlF6 3–.
Fe2O3 1 - 2%
SO3 1 - 2%
14. Biological Importance of
Magnesium and Calcium
 All enzymes that utilise ATP in phosphate transfer require
magnesium as the cofactor
 The main pigment for the absorption of light in plants is
chlorophyll which contains magnesium
 Calcium plays important roles in neuromuscular function,
interneuronal transmission, cell membrane integrity and
Uses: blood coagulation.
Cement has become a commodity of national necessity for any
country next to iron and steel. It is used in concrete and rein-
forced concrete, in plastering and in the construction of bridges,
dams and buildings.

13. Anomalous Behaviour of

Beryllium
Beryllium shows anomalous behaviour as compared to magne-
sium and rest of the members.
(i) Beryllium has small atomic and ionic sizes and thus does
not compare well with other members of the group. Because
of high ionisation enthalpy and small size it forms com-
pounds which are largely covalent and get easily hydroly-
sed.
(ii) Beryllium does not exhibit coordination number more than
four as in its valence shell there are only four orbitals. The
remaining members of the group can have a coordination
number of six by making use of d-orbitals.

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s-Block
s-BLOCK 19

Summary
Atomic and Physical Properties of s block Elements

Property Alkali Metals Trend Alkaline earth metals Trend

Electronic configuration ns1
ns2
Atomic radius Increases down the group Increases down the group
Ionisation energy Decreases down the the group Decreases down group
Hydration energy Decreases down the group Decreases down the group
Ionic Mobility Increases down the group Increases down the group
Melting Point Decreases down the group Irregular
Boiling point Decreases down the group Irregular
Density Increases down the group (exception: K) Increases down the group
Flame colouration Li - Crimson Red Be, Mg - Doesn’t give
Na - Yellow K - Violet, Rb - Red violet Ca - Brick red, Sr - Crimson,
Cs - Blue Ba - Apple green

Chemical Properties of s block Elements

Reaction with Alkali Metals Alkaline earth metals

Excess of Oxygen Li forms monoxide, All form oxides,
Na peroxide and rest superoxide Ba also forms peroxide.
Water Forms hydroxide Forms hydroxide
Air Dry air - corresponding Forms oxide as well as nitride
oxide/peroxide/superoxide (Be and Mg react in powder form)
Moist air - Hydroxide
Li forms nitride also
Hydrogen and halogens Forms ionic hydride Forms ionic hydride
(except Li) and halides respectively and halides
Reducing nature Li - Most powerful Ba - Most powerful
Na - Least powerful Be - Least powerful
Liquid ammonia Forms deep blue conducting solution of Forms deep blue black conducting
ammoniated metal ion and ammoniated solution of ammoniated metal ion
electron and ammoniated electron

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s-Block
20 s-BLOCK

Solved Examples
Example-1  Atomic and ionic radii increase with increase in
What are the common physical and chemical features of atomic number.
alkali metals?  The alkaline earth metals owing to their large size of
Sol. The alkali metals show a regular trend in their physical and atoms have fairly low values of Ionization energy.
chemical properties with the increasing atomic number.  They are harder than alkali metals.
Physical properties of alkali metals:  Electropositive character increases on going down the
group.
 Alkali metals have low melting and boiling point.
 Alkali metals (except Li) exhibit photoelectric effect. Example-3

 Alkali metals impart characteristic colours to the flame. Why are alkali metals not found in nature?
 Alkali metals are silvery white in colour and are generally Sol. Alkali metals are very reactive in nature. They will react
soft and light metals. very fast with air and water. Therefore, they always exist in
 Alkali metals have low ionization enthalpies. combine state not in free state in nature.
 Alkali metals are highly electropositive in nature Example-4
 Alkali metals show +1 oxidation states. Find out the oxidation state of sodium in Na2O2.
 Alkali metals have the largest size in their respective Sol. Oxidation state of sodium in Na2O2:
periods.
Let x be the oxidation state of Na
Chemical properties of alkali metals: Alkali metals are
2x + 2 (-1) = 0
highly reactive elements. The cause for their
(here, oxygen is in peroxide, so we must use the peroxide
high chemical reactivity is:
oxidation state of oxygen)
 Alkali metals have low value of first ionization enthalpy
2x – 2 = 0
 Alkali metals have low heat of atomization. x = +1
 Alkali metals are highly reactive in nature. Example-5
 Alkali metals have strong tendency to get oxidized and Explain why is sodium less reactive than potassium.
acts as strong reducing agents. Sol. Sodium less reactive than potassium due to ionization
 Alkali metals hydroxides are highly basic in nature.
enthalpy.
 Alkali metals dissolve in liquid ammonia and give deep
blue colour solution which are conducting in nature. Ionization enthalpy of sodium = 496 kJ/mol.
Example-2 Ionization enthalpy of potassium = 419 kJ/mol
Discuss the general characteristics and gradation in Ionization enthalpy of potassium is less than that of sodium
due to this potassium is more reactive than sodium.
properties of alkaline earth metals.
Example-6
Sol. The alkaline earth metals have 2 electrons in the s- orbital
Compare the alkali metals and alkaline earth metals with
of the valence shell.
respect to
 The alkaline earth metals are silvery white, lustrous and
(i) ionization enthalpy,
relatively soft but harder than the alkali metals.
(ii) basicity of oxides,
 The hydration enthalpies of alkaline earth metal ions
(iii) solubility of hydroxides.
are larger than those of alkali metal ion.
s-BLOCK 21

Sol. Alkaline earth metals are very much like that of the alkali This property makes Cs and K useful as electrodes in
metals. photoelectric cells.
(i) Ionization enthalpy: Alkaline earth metals is higher than Example-10
alkali metals due to high nuclear charge. the second When alkali metal dissolves in liquid ammonia, the solution
ionization enthalpy of alkaline earth metals is smaller can acquire different colours.Explain the reason for this
than those of the corresponding alkali metals. type of colour change.
(ii) Basicity of oxides: Basicity of oxides of alkali earth metals Sol. All alkali metals dissolve in liquid ammonia and give deep
blue colour solution which are conducting in nature. These
are lower than that of alkaline metals.
solutions contain ammoniated cations and ammoniated
Solubility of hydroxides: Alkali metals are higher than electrons. Ammoniated electrons absorb energy
that of alkaline earth metals. they are soluble in water. corresponding to red region of visible light for their
excitation to higher energy levels
Example-7
 –
M   x  y  NH3   M  NH3  x   e  NH 3  y 
In what ways lithium shows similarities to magnesium in its  
Ammoniated
chemical behaviour? electrons
Sol. The similarity between lithium and magnesium is because Example-11
of their similar sizes; comparable atomic radii and Beryllium and magnesium do not give colour to flame
electronegativities. whereas other alkaline earth metals do so. Why?
Sol. Beryllium and magnesium do not give colour to flame
The major similarities are:
whereas other alkaline earth metals due to the small size,
 Both are harder and lighter than other elements of the ionization enthalpies of Be and Mg are much higher.
the respective groups. Hence, a large amount of energy is required to excite their
 Carbonates of both decompose easily on heating outermost electron. That’s why they do not impart colour
to the flame.
and form oxides and CO2 and both do not form solid
Example-12
hydrogen carbonate.
Discuss the various reactions that occur in the Solvay
 Both LiCl and MgCl2 are soluble in ethanol.
process.
 Both react slowly with water.
Sol. The reaction involved in Solvay process are:
 Both form nitride.
 Both can form complex compounds. NH3 + H2O + CO2 ——— NH4HCO3
Example-8 NaCl+ NH4HCO3 ——— NaHCO3 + NH4Cl

Explain why can alkali and alkaline earth metals not be 2NaHCO3——— Na2CO3 +H2O + CO2
Example-13
obtained by chemical reduction method.
Sol. Alkali and alkaline earth metals are strong reducing agents. Potassium carbonate cannot be prepared by Solvay
That’s why alkali and alkaline earth metals are not obtained process. Why?
by chemical reduction methods. Sol. This is due to the reason that potassium bicarbonate formed
Example-9
as an intermediate (when CO2 is passed through ammoniated
Why are potassium and caesium, rather than lithium used
solution of potassium chloride) is highly soluble in water
in photoelectric cells?
and cannot be separated by filtration.
Sol. The ionization enthalpy of lithium is 520kJ/mol but
potassium and caesium having 419 and 376 kJ/mol. These
elements when irradiated with light, the light energy
absorbed may be enough to make an atom lose electron.
22 s-BLOCK

Example-14 Example-17
Why is Li2CO3 decomposed at a lower temperature whereas Beryllium has …A… Property from rest of alkaline earth
Na2CO3 at higher temperature? metals and show diagonal relationship with …B… Here, A
Sol. The carbonates of alkali metals are quite stable towards and B refer to
heat. Li2CO3 is considerably less stable and decompose (a) Same aluminium
readily on heating due to small polarizes a large carbonate
(b) Different, aluminium
ion leading to the formation of stable Li2O and CO2 on
(c) Sami silicon
heating. As the electropositive character increase down
the group, the stability of carbonates increases. Lattice (d) Different boron

energy of Na2CO3 is higher than that of Li2CO3. Na2CO3 is Ans. (b)

ionic compound and Li2CO3 is a covalent compound. Sol. Beryllium has different property from rest of alkaline earth
Example-15 metals and show diagonal relationship with aluminium..
Give the solubility and thermal stability of the following Example-18
compound of the alkali metals with those of the alkaline The correct reason of expanded coordination number of
earth metals. alkaline earth metal other than beryllium is due to
(a) Nitrates
(a) Presence of vacant p-orbital
Sol. (a) Hydration energy is more than lattice energy due to this
(b) Presence of vacant d-orbital
nitrates of both group 1 and group 2 elements are soluble in
water. (c) Presence of vacant f-orbital in some cases

Nitrates of both group 1 and group 2 elements are thermally (d) All of the above
unstable. Group 1 and 2 nitrates decomposed as follows: Ans. (b)

heat  2NaNO  O Sol. Metal other than Be form more than 4 coordinates complex
2NaNO3  2 2
due to presence of vacant d-orbital.

2KNO  2KNO  O
3 2 2 Example-19

  2LiO  4NO  O Magnesium burns in air to produce MgO and …X… with
4LiNO3  2 2 2
…Y… flame. Here, X and Y refer to

 
2Mg NO  2MgO  4NO  O
3 2 2 2
(a) Mg2N3, Oxidizing
Example-16
(b) Mg3N2, reducing
…X and …Y…Shown diagonal similarity.
(c) Mg3N2, dazzling
Here, X and Y refer to
(d) Mg2N3, dazzling
(a) Lithium and magnesium
Ans. (c)
(b) Lithium and beryllium
Sol. Mg is more electropositive metal and buns withdazzling
(c) Sodium and magnesium flame in air to give MgO and Mg3N2.
(d) None of these
Ans. (a)
Sol. Lithium and magnesium shows similarity in many of their
properties hence, they are diagonally related to each other.
s-BLOCK 23

Example-20 IV. Biological function of s-block elements is due to

Which of the following is correctly represented according maintenance of ion balance and nerveimpulse condition.
to their existence? (a) Only I
I. MgCl2 .6H2O II. NaCl. 6H2O (b) II and III
III. KCl. 6H2O IV. CaCl2. 6H2O (c) II and III
(a) I and II (b) II and III (d) Only III
(c) II and IV (d) I and IV Ans. (c)
Ans. (d) Sol. Statement II and III are incorrect, because Oxides and
Sol. MgCl2 and CaCl2 exist as hydrates while KCl and NaCl hydroxides of alkaline earth metals and alkali metal are
does not exist in the hydrate form. alkaline in nature.
Example-21
Apart from Na and K, Ca and Mg are also found in biological
Which of the following is/are correct statement(s) regarding fluid.
carbonates of alkaline earth metals? Example-23
I. They are thermally unstable Match the column I with Column II and choose the correct
II. They are insoluble in water option from the codes given below.
III. They cannot be precipitated by adding sodium or
Column I Column II
ammonium carbonate.
A.Sodium 1. Present in biological fluid
IV. Beryllium carbonate is thermally unstable.
B.Beryllium 2. Radioactive element
(a) I, II and III are correct
C.Francium 3. Lower abundance
(b) II and IV are correct
D. Calcium 4. Alkali metals
(c) I, II and IV are correct
5. Alkaline earth metal
(d) All are correct
A B C D
Ans. (c)
Sol. Statement III is incorrect because carbonates can be (a) 1 4 2 5

precipitated by addition of sodium or ammonium carbonate (b) 1 2 3 4

due to common ion effect. (c) 3 1 2 5
Example-22
(d) 4 5 2 1
Which of the following statements(s) is/are incorrect
Ans. (d)
regarding the s-block elements?
Sol. Correct matching is represented as
I. Francium is highly radioactive element.
A. Sodium- Alkali metal
II. Oxides and hydroxides of alkali metals and alkaline earth
metals are not alkaline in nature. B. Beryllium- Alkaline earth metal

III. Sodium and potassium are the only two s- block C. Francium- radioactive element
elements are found in large proportion in biological D. Calcium - Present in biological fluid
fluids.
24 s-BLOCK

Example-24 Example-25
Milk of lime reacts with chlorine to form …A…a constituent Which of the following is/are correct statement (s)?
of …B… Here, A and B refer to (a) Ca3(PO4)2 is part of bones
(a) Hypochlorite, cement (b) 3Ca3(PO4).CaF2 is part of enamel on teeth
(b) Hypochlorite, bleaching powder (c) Ca2+ ions are important in blood clotting
(c) Hypochlorite, bleaching powder (d) All of the above are correct
(d) Hypochlorous cement Ans. (d)
Ans. (b) Sol. All the given statement are correct.
Sol. Milk of lime i.e., Ca(OH)2 reacts with chlorine to form Ca3(PO4)2 is part of bones
hypochlorite Ca(OCl2) which is a constituent of bleaching
3Ca3(PO4).CaF2 is part of enamel on teeth
powder.
Ca2+ ions are important in blood clotting
Ca  OH 2  2Cl 2  CaCl 2  CaOCl 2  2H 2 O
s-BLOCK 25

EXERCISE – 1: Basic Objective Questions

(b) Increasing s-elements
Introduction of s block Elements (c) Decreasing atomic number
(d) Decreasing s-elements
1. s-subshell can accommodate maximum number of
10. All alkaline metals have …A… valence electrons(s).
(a) Zero electrons (b) Two electrons
Here, A refer to
(c) One electrons (d) None of these
(a) 0 (b) 1
2. Group I elements are collectively known as
(c) 2 (d) Both (a) and (b)
(a) Alkali metals (b) Alkaline earth metals
11. Alkali metals readily …X… electron to give
(c) Both (a) and (b) (d) None of these
monovalent M+ ion. Here, X refer to
3. Group II elements with exceptions of beryllium are
(a) Gain (b) Iose
known as alkaline earth metals. These are so called
(c) Neither (a) nor (b) (d) Both (a) and (b)
because their …A…and …B… are alkaline in nature.
12. Alkali metals have …X… size in a particular period.
Here, A and B refer to
Here, X refer to
(a) Oxides, halides (b) Oxides, hydroxides
(a) Smaller (b) Largest
(c) Halides, hydroxides (d) None of these
(c) Smallest (d) None of these
4. Among the alkali metals …A and …B… are relatively
13. Monovalent ions are …A…than parent atom. Here, A
more abundant in nature. Here A and B refer to
refers to
(a) Sodium and rubidium (b) Lithium and sodium
(a) Smaller (b) Larger
(c) Sodium and potassium (d) Lithium and potassium
(c) Heavier (d) None of these
5. Which of the following does not belong to alkaline
14. Atomic and ionic radii of alkali metals …X… on
earth metal?
moving down the group. Here, X refer to
(a) Beryllium (b) Strontium
(a) Increase (b) Decrease
(c) Francium (d) Calcium
(c) Remains same (d) None of these
6. …X and …Y…Shown diagonal similarity. Here, X and
15. The ionization enthalpies of alkali metals are
Y refer to
considerably
(a) Lithium and magnesium
(a) High (b) Low
(b) Lithium and beryllium
(c) Highest (d) None of these
(c) Sodium and magnesium
16. The correct decreasing order of ionization enthalpy in
(d) None of these
alkali metals is
7. Which of the following shows diagonal relationship?
(a) Na>Li>K>Rb (b) Rb>Na>K>Li
(a) Magnesium and aluminium
(c) Li>Na>K>Rb (d) K>Li>Na>Rb
(b) Beryllium and aluminium
17. …A… has maximum degree of hydration. Here, A
(c) Sodium and magnesium
refers to
(d) None of these
(a) Fr+ (b) Na+
8. The diagonal relationship of elements arises due to the +
(c) Li (d) K+
similarity in
18. Which of the following metal salt is mostly hydrated?
(a) Ionic sizes (b) Charge/radius ratio
(a) Na (b) Li
(c) Both (a) and (b) (d) None of these
(c) Fr (d) K
19. Which of the following choice(s) represents(s) physical
Physical and Chemical Properties of Alkali
properties of alkali metals?
Metals (a) They are silvery white coloured
(b) They are soft
9. Alkali metals show regular trend in their physical and (c) They are light metals
chemical properties with the (d) All of the above
(a) Increasing atomic number
26 s-BLOCK

20. Along the group in alkali metals the density (a) I and II (b) I, II and III
(a) Decreases top to bottom (c) II and IV (d) I, II and IV
(b) Increase top to bottom 27. Which of the following elements(s) form stable
(c) Remains same superoxide?
(d) Follow an irregular trend (a) K (b) Rb
21. The low melting point of alkali is due to (c) Cs (d) All of these
(a) Weak metallic bonding 28. Alkali metals are kept in kerosene oil. Which of the
(b) Presence of only one valence electron following reason (s) is/are correct regarding this
(c) Both (a) and (b) statements?
(d) None of above (a) Due to high reactively of alkali metal
22. The alkali metals and their salts show characteristics (b) Due to high ionization enthalpy of alkali metals
colour to (c) Due of large size of alkali metals
(a) An oxidizing flame (b) A reducing flame (d) Both (a) and (b)
(c) Both (a) and (b) (d) None of these 29. The oxidation state of K in KO2 is …A… and the
23. Choose the correct option from the codes given below bonding type is …B… Here, A and B refer to
regarding elements and their characteristics colour (a) -1 and ionic respectively
given in Column I and II of the following table. (b) +1 and covalent respectively
Column I Column II (c) +2 and ionic respectively
A. Li 1. Crimson red (d) +1 and ionic respectively
B. Na 2. Yellow 30. Alkali metal reacts with water vigorously to form
C. K 3. Red violet hydroxides and dihydrogen. Which of the following
alkali metals reacts with water least vigorously?
D. Rb 4. Violet (a) Li (b) Na
(c) K (d) Cs
A B C D 31. The nature of bonding in hydride of alkali metal is
(a) 2 1 3 5 (a) Covalent (b) Ionic
(b) 1 2 4 3 (c) Electrovalent (d) Coordinate
(c) 1 2 4 3 32. Lithium halides are somewhat …A… It is because
(d) 1 2 3 4 …B… value of polarization capability of lithium ion.
24. Alkali metals can be detected by their respective …A… Here, A and B refer to
Here, A refer to (a) Ionic, Low (b) Ionic, High
(a) Lassaigne test (c) Covalent, Low (d) Covalent, High
(b) Flame test 33. Which of the following metal has high value of
(c) Emission test polarization?
(d) Both (a) and (b) (a) Sodium ion (b) Potassium ion
25. Which of the following element(s) is used as useful (c) Cesium ion (d) Lithium ion
electrode(s) in photoelectric cells? 34. Which of the following is correct metals regarding least
(a) Sodium (b) Cesium and most powerful reducing agent among alkali metals?
(c) Potassium (d) Both (b) and (c) (a) Lithium, sodium (b) Lithium, potassium
26. Choose the correct statements(s) among the following. (c) Lithium, cesium (d) Cesium, lithium
I. Alkali metal is highly reactive. 35. Alkali metals dissolve in liquid ammonia and produces
II. Alkali metal has lowest ionization enthalpy among (a) Deep blue solution
their respective period. (b) A solution which are conducing in nature
III. Ionization energy of alkali metals increases top to (c) Red coloured solution
bottom. (d) Both (a) and (b)
IV. Superoxide ions is stable only in the presence of
large cations.
s-BLOCK 27

36. When sodium is dissolved in liquid ammonia is solution 42. Choose the correct statements (s) regarding lithium and
of deep blue colour is obtained. The colour of solution alkali metals
is due to I. Lithium is much harder. Its m.p and b.p are higher
(a) Ammoniated electron than other alkali metals.
(b) Sodium ion II. Lithium is highly reactive and strongest reducing
(c) Sodium amide agent.
(d) Ammoniated sodium ion III. Lithium is deliquescent and crystallizes as
37. Which of the following metal is used to form useful hydrates.
alloys? IV. LiF is comparatively less soluble in water.
(a) Na (b) K (a) I, III and IV are correct
(c) Li (d) All of these (b) II and III are correct only
38. …A…is used in the manufacturing of soft soap. Here, (c) I is correct only
A refer to (d) All are correct
(a) Sodium hydroxide (b) Potassium hydroxide 43. Alkali metal nitrates decomposes to produce …X…
(c) Lithium hydroxide (d) Both (a) and (b) while lithium nitrate on heating decomposes to
39. …A… is used in devising photoelectric cells. Here, A corresponding …Y… Here, Y and Y refer fo
refer to (a) Oxides and oxide (b) Nitrite and oxide
(a) Lithium (b) Sodium (c) Nitrates and nitrite (d) Monoxide and nitrites
(c) Cesium (d) Potassium 44. Similarity between lithium and magnesium is
40. Match the Column I and Column II and choose the particularly stricken and arises because of their
correct option from the codes give below. (a) Small hydration energies
Column I Column II (b) High hydration energies
A. Potassium 1. Soft soap (c) Low ionization energies
B. Potassium (d) Similar sizes
2. Fertilizer
chloride 45. Lithium and magnesium oxides and hydroxides are
C. Potassium …X… soluble in water. Here, X refers to
3. Photoelectric cells (a) Less (b) Not
hydroxide
4. Biological nerve impulse (c) Most (d) None of the above
D. Cesium 46. Choose the incorrect statement out of the following
condcution
(a) LiCl and MgCl2 are soluble in ethanol
A B C D (b) LiCl and MgCl2 are deliquescent and crystallizes
(a) 4 2 1 3 from aqueous solutions as hydrates
(b) 3 1 2 4 (c) Li2O and MgO combines with excess oxygen to
(c) 2 3 1 4 produce superoxide
(d) 4 2 3 1 (d) Carbonates of Li and Mg decomposes easily on
heating to form oxides and CO2

Anomalous Properties of Lithium

General Characteristics of the Compounds of
41. Anomalous behavior of lithium is due to Alkali metals
I. exceptionally small size of its atom
II. High polarizing power. 47. On combustion in excess of air lithium forms mainly
…X… sodium forms …Y… while potassium forms
Charge
III. High ratio. …Z…Here, X, Y and Z refer to
Radius
(a) Oxides, superoxide, peroxides
Choose the correct option
(b) Superoxide, Peroxide, oxide
(a) I and II are correct (b) I and II are correct (c) Peroxide, superoxide, oxide
(c) II and III are incorrect (d) All are correct (d) Oxide, peroxide, superoxide
28 s-BLOCK

48. Sodium …X… is widely used as a/an …Y…. Here, X 55. Which of the following is correct regarding salt of oxo-
and Y refer to acids of alkali metals?
(a) Oxides, oxidizing agent (a) In oxo-acid are those in which the acidic proton is
(b) Oxides, reducing agent on a hydroxyl group with an oxo group attached to
(c) Superoxide, reducing agent same atom
(d) Peroxide, oxidizing agent (b) Carbonic acid is an oxo-acid
49. The alkali metal oxides dissolve in water to produce (c) They are generally soluble in water
(a) Basic solution (d) All the above are correct
(b) Acidic solution 56. The carbonates and hydrogen carbonates of alkali
(c) Amphoteric solution metals are highly stable, their stability
(d) None of these (a) Decreases from top to bottom
50. Which of the following statement (s) is/are correct (b) Increases from top to bottom
regarding alkali metal halides? (c) Remain same
I. They possess high melting point and are crystalline (d) None of above
in nature. 57. Lithium being very small in size, which …A… a large
II. They are prepared by reaction of appropriate CO 32  ion leading to the formation of more stable …B..
oxides with aqueous hydrohalic acid. and …C.. Here A, B and C refer to
III. They are prepared by reaction of carbonates with (a) Polarises, Li2O and CO
aqueous hydrohalic acid (b) Polarises, Li2O and CO2
IV. They have high negative enthalpy of formation. (c) Dissociate, Li2O and CO
(a) I and II are true (b) I, II and are true (d) Dissociate, Li2O and CO2
(c) II, III and IV are true (d) All the above are true
51. Choose the correct statement/statement out of the
following Some Important Compounds of Sodium
(a)  l H  always became less negative on moving top
58. Solvay process is used in the preparation of
to bottom for alkali halides
(a) Sodium carbonate
(b)  l H  always becomes less negative from fluoride (b) Potassium carbonate
to iodide for alkali metals (c) Cesium carbonate
(c) LiHCO3 doesn’t exist in solid state (d) Rubidium carbonate
(d) All the above are true 59. What will be the product when ammonium chloride is
52. The correct trend of melting point and boiling point of treated with calcium hydroxide?
alkali metal halides (a) Ammonia (b) Calcium chloride
(a) Fluoride > chloride > bromide > iodide (c) Both (a) and (b) (d) None of these
(b) Fluoride < chloride > bromide < iodide 60. Potassium is not prepared by Solvay process because
(c) Fluoride < chloride < bromide < iodide …X… is too soluble to be precipitated by addition of
(d) Fluoride < chloride < bromide < iodide ammonium hydrogen carbonate. Here, X refer to
53. Low solubility of LiF in water is due to …A… Here, A (a) KHCO3 (b) NH4HCO3
refer to (c) K2CO3 (d) None of these
(a) Low lattice energy (b) High hydration energy 61. Which of the following is known molecular formula of
(c) Low hydration energy (d) High lattice energy washing soda?
54. Low solubility of CsI is due to (a) Na2CO3.10H2O (b) Na2CO3.7H2O
(a) Low lattice energy (c) NaHCO3.10H2O (d) NaHCO3.7H2O
(b) High lattice energy 62. Which of the following exist as decahydrate?
(c) Low hydration energy (a) Caustic soda (b) Washing soda
(d) High hydration energy (c) Brine solution (d) Baking soda
s-BLOCK 29

63. Above 373K, the monohydrate sodium hydrogen 72. Which of the following statement is incorrect regarding
carbonate becomes completely anhydrous and called as use of caustic soda?
(a) Potash ash (b) Soda ash (a) It is used in purification of bauxite
(c) Pearl ash (d) Brine ash (b) It is used in textile industry
64. Sea water contain…by mass of the salt (NaCl) (c) It is used in preparation of ammonia
(a) 2.7 to 2.9 % (b) 5.7 to 7.9 % (d) It is used in manufacture of soap and paper
(c) 6.0 to 9.0 % (d) None of these 73. Which of the following is used in the preparation of
65. Crude…A… Generally obtained by crystallization of cakes or pastries?
brine solution. Here, A refers to (a) Sodium hydrogen carbonate
(a) Potassium chloride (b) Calcium chloride (b) Sodium carbonate
(c) Sodium chloride (d) Both (a) and (b) (c) Sodium hydroxide
66. Which of the following is present as impurity in crude (d) Potassium hydroxide
sodium chloride? 74. The formula of soda ash is
(a) Magnesium chloride (b) Calcium chloride (a) Na2CO3.10H2O (b) Na2CO3.2H2O
(c) Sodium sulphate (d) All of these (c) Na2CO3.H2O (d) Na2CO3
67. Solubility of sodium chloride in 100 g of water at 273
K is Biological Importance of Sodium and Potassium
(a) 26.0 g (b) 36.0 g
(c) 46.0 g (d) 50.0 g
75. A 70 Kg man contain about …X… of Na and …Y… of
68. Which of the following is commonly named as caustic
K. here, X and Y refer to
soda?
(a) 170 g and 70g (b) 70 g and 170 g
(a) Sodium hydrogen carbonate, dehydrate
(c) 90 g and 170 g (d) 170 g and 90 g
(b) Sodium carbonate, decahydrate
76. Sodium ions found primarily in which part of human
(c) Sodium chloride
body?
(d) Sodium hydroxide
(a) Outside of cells (b) In blood plasma
69. Sodium hydroxide is commercially prepared by
(c) In interstitial fluid (d) All of these
(a) Electrolysis of sodium bicarbonate
77. Which of the following ion is most abundant within cell
(b) Electrolysis of sodium chloride
fluid?
(c) Electrolysis of sodium carbonate
(a) Sodium ion
(d) None of the above
(b) Potassium ion
70. Sodium chloride is prepared by the electrolysis of
(c) Both are equally abundant
sodium chloride solution the electrodes used as cathode
(d) None of these
and anode are respectively.
78. Which of the following statement (s) is/are correct?
(a) Mercury and platinum
I. Sodium and potassium are found on same sides of
(b) Platinum and Mercury
cell.
(c) Mercury and carbon
II. Sodium and potassium are present on opposite side
(d) Carbon and Mercury
of cell.
71. Which of the following statements(s)is/are correct
III. Sodium is found in blood plasma and potassium is
regarding sodium hydroxide?
found in RBC.
I. It is white and translucent.
IV. Sodium and potassium operates sodium-potassium
II. It melts at 591K.
pump across the membrane.
III. It is non-deliquescent
(a) I and III
IV. It is soluble in water and its aqueous solution is
(b) II, III and IV
highly basic in nature.
(c) III and IV
(a) I and III (b) II and IV
(d) All of these are correct
(c) I, III and IV (d) I, II and IV
30 s-BLOCK

79. What approximate amount of ATP is used by a resting 88. Which of the following is correctly order regarding
human in 24 hours? hydration enthalpies of alkaline earth metals?
(a) 27 Kg (b) 50 Kg (a) Be2+ <Mg2+ <Ca2+ <Sr2+ <Ba2+
(c) 15 Kg (d) 30 Kg (b) Be2+ >Mg2+ >Ca2+ >Sr2+ >Ba2+
(c) Be2+ <Mg2+ >Ca2+ >Sr2+ >Ba2+
Group II Elements: Alkaline Earth Metals (d) Mg2+ >Be2+ >Ca2+ <Sr2+ >Ba2+
89. Hydration energy of alkaline earth metal has …A…
80. Beryllium has …A… Property from rest of alkaline value to that of alkali metal. Here, A refer to
earth metals and show diagonal relationship with (a) Higher
…B… Here, A and B refer to (b) Lower
(a) Same aluminium (b) Different, aluminium (c) Similar
(c) Sami silicon (d) Different boron (d) None of the above
81. Which of the following is not an alkaline earth metal? 90. Assertion (A) The compounds of alkaline earth metals
(a) Ba (b) Ca are more extensively hydrated than those of alkali
(c) Fe (d) Mg metal.
82. Ground state valence shell electronic configuration of Reason (R) This is due to low hydration energy of
barium is alkaline earth metal as compared to alkali metal.
(a) 6s2 (b) 5s2 (a) Both A and R are correct; R is the correct
(c) 7s 2
(d) 4s2 explanation of A
83. Nature of bonding present in compounds of alkaline (b) Both A and R are correct; R is not the correct
earth metals are explanation of A
(a) Ionic (c) A is correct; R is incorrect
(b) Covalent (d) R is correct; A is incorrect
(c) May be ionic or covalent 91. Which of the following is correctly represented
(d) None of the above according to their existence?
84. The atomic and ionic radii of the alkaline earth metals I. MgCl2 .6H2O
are …A… than those of the corresponding alkali metals II. NaCl. 6H2O
in the corresponding period Here, A refers to III. KCl. 6H2O
(a) Lower (b) Higher IV. CaCl2. 6H2O
(c) Same (d) Irregular to (a) I and II
85. The alkaline earth metals have smaller size than those (b) II and III
of corresponding alkali metals, this is due to (c) II and IV
(a) Increase in ionization enthalpy (d) I and IV
(b) Decrease in nuclear charge 92. Alkaline earth metals are …X… than that of alkali
(c) Increase in nuclear charge metals. Here, X refer to
(d) Increase in number of shells (a) Harder (b) Softer
86. Along the group, size and ionization enthalpy of the (c) Light (d) None of the above
group II elements(s) … and … respectively. 93. Alkali metals are generally silvery white but beryllium
(a) Increase, Decreases (b) Decrease, Increases and magnesium appears to be
(c) Increases, Increases (d) Decreases, Decreases (a) Reddish (b) Greyish
87. The first ionization enthalpy of the alkaline earth metals (c) Yellowish (d) None of the above
are …X…. that of corresponding group I metal. Here, 94. Melting and boiling point of the alkaline earth metal are
X refers to …X… than the corresponding alkali metal due to
(a) Smaller than …Y… sizes. Here, X and Y refer to
(b) Higher than (a) Higher, smaller (b) Lower, Larger
(c) Same as (c) Lower, Smaller (d) Higher, larger
(d) None of the above
s-BLOCK 31

95. Match the Column I and Column II according to 103. Which of the following is known as milk of magnesia?
element and their characteristics colours, appears in (a) Suspension of hydroxide of magnesium in water
flame test and select the correct option from the codes (b) Suspension of chloride of magnesium in water
given below. (c) Suspension of carbonates of magnesium in water
Column I Column II (d) None of the above
A. Ca 1. Apples green 104. Which of the following is used in radiotherapy?
B. Sr 2. Crimson (a) Barium salt
C. Ba 3. Brick red (b) Calcium salt
(c) Radium salt
A B C
(d) Strontium salt
(a) 1 2 3
105. Which of the following is used as antacid in medicine?
(b) 3 1 2
(a) Milk of magnesia
(c) 3 2 1
(b) Suspension of hydroxide of magnesium in water
(d) 1 3 2
(c) Suspension of hydroxide of calcium in water
96. eryllium and magnesium do not impart any colour to
(d) Both (a) and (b)
the flame test. The reason is that
106. Match the Column I and Column II and choose the
(a) Lower value of ionization value
correct option from the codes given below.
(b) Higher value of ionization energy
(c) Larger size of alkali earth metal Column I Column II
(d) Both (b) and (c) are correct A. Cu-Be alloy 1. High strength spring
97. Beryllium and Magnesium are kinetically inert to B. Magnesium
2. Used as antacid in medicine
oxygen and water because of formation of …X.. on ribbon
their surface. Here, X refer to C. Milk of
3. Toothpaste
(a) Oxide film (b) Hydroxide film magnesia
(c) Hydrated salt (d) All of the above D.Magnesium
4.Bulbs
98. Powder of beryllium burns in air frequently to produce carbonate
(a) BeO (b) Be3N2 A B C D
(c) Both (a) and (b) (d) None of the above (a) 1 2 3 4
99. Magnesium burns in air to produce MgO and …X… (b) 4 3 2 1
with …Y… flame. Here, X and Y refer to (c) 1 4 2 3
(a) Mg2N3, Oxidizing (b) Mg3N2, reducing (d) 1 2 4 3
(c) Mg3N2, dazzling (d) Mg2N3, dazzling
100. BeH2 can be prepared by
Anomalous Behaviour of Beryllium
(a) Reaction of beryllium with H2 gas
(b) Reaction of beryllium with LiAiH 4
107. Assertion (A) Compounds of beryllium is largely
(c) Reaction of BeCl2 with H2
covalent and get hydrolyzed easily.
(d) All of the above
Reason (R) This is due to high value of ionization
101. Which of the following reason is correct regarding
value and small size.
reducing nature of beryllium?
(a) Both A and R are correct; R is the correct
(a) Large value of hydration energy
explanation of A
(b) Small size of Be2+
(b) Both A and R are correct; R is not the correct
(c) Large value of enthalpy of atomization
explanation of A
(d) All of the above
(c) A is correct; R is incorrect
102. Colour of solution prepared by dissolution of alkaline
(d) R is correct; A is incorrect
earth metal on ammonia solution
(a) Blue (b) Deep blue black
(c) Bronze (d) Brown
32 s-BLOCK

108. Beryllium does not exhibit coordination number more 113. Oxides and other compound of beryllium and
than 4 as in its valence shell there are only 4 orbitals. magnesium are …X… than those of rest heavier large
The remaining members of the group can have a sized atom.
coordination number …X… by making use of …Y… (a) More ionic (b) More covalent
Here, X and Y refer to (c) Lest covalent (d) None of these
(a) 6, d-orbital (b) 4, p-orbital 114. Which of the following has not rock salt type structure?
(c) 6, f-orbital (d) None of these (a) MgO (b) BeO
109. Assertion (A) Beryllium and aluminum show diagonal (c) BaO (d) CaO
relationship. 115. Which of the following is amphoteric?
Reason (R) This is due to exactly same charge/radius (a) BeO (b) CaO
ratio. (c) MgO (d) SrO
(a) Both A and R are correct; R is the correct 116. Metal form basic hydroxides. Which of the following
explanation of A metal hydroxide is the least basic?
(b) Both A and R are correct; R is not the correct (a) Mg(OH)2 (b) Ca(OH)2
explanation of A (c) Sr(OH)2 (d) Ba(OH)2
(c) A is correct; R is incorrect 117. Assertion (A) Fluorides are less soluble than chlorides.
(d) R is correct; A is incorrect Reason (R) this is due to less hydration energy of
110. Assertion (A) Beryllium is not readily attacked by acid. fluoride.
Reason (R) This is because of presence of hydroxide (a) Both A and R are correct; R is the correct
film over surface of metal. explanation of A
(a) Both A and R are correct; R is the correct (b) Both A and R are correct; R is not the correct
explanation of A explanation of A
(b) Both A and R are correct; R is not the correct (c) A is correct; R is incorrect
explanation of A (d) R is correct; A is incorrect
(c) A is correct; R is incorrect 118. Which of the following is/are correct statement(s)
(d) R is correct; A is incorrect regarding carbonates of alkaline earth metals?
111. The chlorides of both beryllium and aluminium are I. They are thermally unstable
soluble in …X… solvent and are …Y… Here X and Y II. They are insoluble in water
are III. They cannot be precipitated by adding sodium or
(a) Aqueous, Lewis base (b) Aprotic, amphoteric ammonium carbonate.
(c) Organic. Lewis acid (d) Organic. Lewis base IV. Beryllium carbonate is thermally unstable.
(a) I, II and III are correct
General Characteristics of Compounds of (b) II and IV are correct
Alkaline Earth Metals (c) I, II and IV are correct
(d) All are correct
119. Which of the carbonate given below is unstable in air
112. Assertion (A) Compounds of alkaline earth metal are
and kept in CO2 atmosphere to avoid decomposition?
less ionic than the compounds of alkali metals
(a) BeCO3 (b) MgCO3
Reason (R) this is due to small size and increased
(c) CaCO3 (d) BaCO3
nuclear charge of alkaline earth metal.
(a) Both A and R are correct; R is the correct
explanation of A
(b) Both A and R are correct; R is not the correct
explanation of A
(c) A is correct; R is incorrect
(d) R is correct; A is incorrect
s-BLOCK 33

120. Assertion (A) BeSO4 and MgSO4 are readily soluble in (d) Ca(HCO3)2, Castner-Kelliner cell
water. 126. Which of the following statement(s) is/are correct
Reason (R) This is due to greater hydration enthalpies regarding oxide of calcium?
of Be2+ and Mg2+ ions which overcome the lattice (a) It is a white amorphous solid
enthalpy factor. (b) It has melting point of 2870 K
(a) Both A and R are correct; R is the correct (c) It absorbs moisture and CO2 from atmosphere
explanation of A (d) All the above are correct.
(b) Both A and R are correct; R is not the correct 127. The addition of limited amount of water breaks the
explanation of A lump of lime. This process is called.
(c) A is correct; R is incorrect (a) Electrolysis of lime (b) Hydrolysis of lime
(d) R is correct; A is incorrect (c) Slaking of lime (d) None of these
121. Nitrates of alkaline earth metals can be prepared by 128. Quick lime slaked with soda gives
dissolution of …A.. in dilute nitric acid. Here. A refer (a) Solid sodalime (b) Slaked lime
to (c) Plaster of Paris (d) None of these
(a) Hydroxide of alkaline earth metal 129. Quick of the following is the use of quick lime?
(b) Oxides of alkaline earth metal (a) It is used in the manufacture of sodium carbonate
(c) Carbonates of alkaline earth metal from caustic soda
(d) All of the above (b) It is an important primary material for
122. Choose the incorrect statement(s). manufacturing of cement
(a) Nitrate of magnesium crystallizes with six water (c) It is employed in the purification of sugar and
molecules manufacturing of dyestuff
(b) Barium nitrate is crystallizes in anhydrous (d) All of the above
condition. 130. Suspension of slaked lime in water is known as
(c) Nitrates of alkaline earth metal decomposes on (a) Lime water
heating to produce monoxide (b) Quick lime
(d) Barium sulphate is highly soluble in water (c) Milk of lime
123. Choose the correct statement(s) in following regarding (d) Aqueous solution of slaked lime
compounds of alkaline earth metals. 131. Milk of lime reacts with chlorine to form …A…a
I. Solubility of sulphate of Ca to Ba decreases constituent of …B… Here, A and B refer to
progressively. (a) Hypochlorite, cement
II. Solubility of carbonates in water increase top to (b) Hypochlorite, bleaching powder
bottom in a group. (c) Hypochlorite, bleaching powder
III. Hydrate forming tendency of alkaline earth metal (d) Hypochlorous cement
decreases top to bottom. 132. Which of the following statements in true about
(a) I and II are correct (b) II and III are correct Ca(OH)2?
(c) I and III are correct (d) All are correct (a) It is used in the preparation of bleaching powder
124. The decomposition temperature is maximum for (b) It is a light blue solid
(a) MgCO3 (b) CaCO3 (c) It does not possess disinfectant property
(c) BaCO3 (d) SrCO3 (d) It is used in the manufacture of cement
133. Calcium carbonate can be prepared by passing carbon
Some Important Compounds of Calcium dioxide through…A… or by the addition of sodium
carbonate to …B… Here, A and B refer to
125. Calcium oxide is prepared by heating …A… in a (a) Slaked lime, calcium chloride
…B… at 1070-1270 K. Here, A and B refer to (b) Calcium chloride, slacked lime
(a) CaCO3, Castner-Kelliner cell (c) lime, calcium chloride
(b) CaCO3, rotary kiln (d) Calcium chloride, quick lime
(c) Ca(HCO3)2 rotary kiln
34 s-BLOCK

134. …A…Along with …B… is used as a flux in the (a) Ca2SiO4 (b) Ca3SiO5
extraction of metals. Here, A and B refer to (c) Ca3Al2O6 (d) Ca3(PO4)3
(a) Calcium carbonate, Strontium carbonate 144. Setting of cement occurs due to the presence of
(b) Magnesium carbonate, calcium carbonate (a) Gypsum (b) Cement clinker
(c) Calcium carbonate, magnesium carbonate (c) Clay (d) All of the above
(d) None of the above Biological Importance of Mg and Ca
135. Dead burnt plaster is
1 145. Which of the following element is in most abundant in
(a) CaSO4 (b) CaSO4 . H2 O
2 human body?
(c) CaSO4 .H2 O (d) CaSO4 .2H2 O (a) Na (b) K
136. Molecular formula of plaster of Paris is (c) Ca (d) Mg
146. All enzyme that utilizes ATP in phosphate transfer
1
(a) CaSO4 (b) CaSO4 . H2 O require a cofactor i.e.,
2
(a) Potassium (b) Calcium
(c) CaSO4 .H2 O (d) None of these
(c) Sodium (d) Magnesium
137. By adding gypsum to cement 147. Which of the following element is present in excess
(a) Setting time of cement becomes less amount in human bones and teeth?
(b) Setting time of cement becomes increases (a) Sodium (b) Potassium
(c) Colour of cement become light (c) Calcium (d) Carbon
(d) Shining surface is obtained 148. The main pigment of the absorption of light in plants is
138. Percentage of CaO present in Portland cement is …A…Which contains ….B….Here, A and B refer to
(a) 50-60% (b) 70-80% (a) Chlorophyll, Mg
(c) 90% (d) 40% (b) Chlorophyll, Mn
139. Which of the following is not an use of plaster of Paris? (c) Chlorophyll, Ca
(a) As a disinfectant (d) None of the these
(b) In dentistry and ornamental work 149. Which of the following is not a biological function of
(c) Bone fracture and sprain calcium?
(d) Building industry (a) Neuromuscular
140. For a food quality of cement, ratio of silica (SiO2) and (b) Interneutronal transmission
alumina (Al2O3) should be (c) Blood coagulation
(a) 3 to 7 (b) 7 to 9 (d) Interstitial fluidity control
(c) 2.5 to 4 (d) None of these 150. Which of the following hormone(s) is/are responsible
141. For a good quality of cement, ratio of lime (CaO) to for maintenance of calcium concentration in plasma?
total of oxide of silico (SiO2) aluminium (Al2O3) and (a) Calcitonin
iron (Fe2O3) should be as close to (b) Parathyroid
(a) 2 (b) 3 (c) Both (a) and (b)
(c) 4 (d) 5 (d) None of the above
142. When clay and lime stone are strongly heated they
produces
(a) Cement clinker (b) Gypsum
(c) Portland cement (d) Tricalcium silicate
143. Which of the following is not an important ingredient
present in Portland cement?
s-BLOCK 35

EXERCISE – 2: Previous Years Questions

1. Which one of the following properties of alkali metals (a) SrCl2 (b) BaCl2
increases in magnitude as the atomic number reises? (c) MgCl2 (d) CaCl2
(AIPMT 1989)
10. The correct order of stability for the following
(a) Ionic radius (b) Melting point
superoxides is (EAMCET 2008)
(c) Electronegatiity (d) First ionization energy
(a) KO2 > RbO2 > CsO2
2. Which compound will show the highest lattice energy?
(AIPMT 1993) (b) RbO2 > CsO2 > KO2
(a) RbF (b) CsF (c) CsO2 > RbO2 > KO2
(c) NaF (d) KF (d) KO2 > CsO2 > RbO2
3. Main process for the manufacture of sodium carbonate
is (MP PMT 2006) 11. Which of the following on thermal decomposition
(a) Nelson process (b) Down’s process yields a basic as well as an acidic oxide?
(c) Castner process (d) Solvay process
(Kerala CEE 2008)
4. When sodium nitrate is heated above 800° C then (a) KClO3 (b) Na2CO3
(JCECE 2006)
(c) NaNO3 (d) CaCO3
(a) only Na2O is formed (b) only N2 is formed
12. The solubilities of carbonates decrease down the
(c) only O2 is formed (d) All are formed
magnesium group due to a decrease in (RPMT 2008)
5. Lower melting point chloride is (JCECE 2006) (a) lattice energies of solids.
(a) LiCl (b) NaCl (b) hydration energies of cations
(c) KCl (d) CsCl (c) inter-ionic attraction
6. Consider the following abbreviations for hydrated (d) entropy of solution formation.
What is the correct order of size of these hydrated alkali 13. Which of the following oxides is not expected to react
ions? with sodium hydroxide? (CBSE AIPMT 2009)
  
x   Li  H 2 O n  , y   Na  H 2 O n  , z   K  H 2 O n  (a) B2O3 (b) CaO
(J & K CET 2006) (c) SiO2 (d) BeO
(a) X > Y > Z (b) Z > Y > X 14. In the case of alkali metals, the covalent character
(c) X = Y = Z (d) Z > X > Y decreases in the order, (CBSE AIPMT 2009)
7. In which of the following the hydration energy is higher (a) MCl > MI > MBr > MF
than the lattice energy? (CBSE AIPMT 2007) (b) MF > MCl > MBr > MI
(a) BaSO4 (b) MgSO4 (c) MF > MCl > MI > MBr
(c) RaSO4 (d) SrSO4 (d) MI > MBr > MCl > MF
8. The alkali metals from salt-like hydride by the direct 15. Which physical property in the alkali metal group
synthesis at elevated tempeature. The thermal stability increases with atomic number? (AMU 2009)
of these hydrides decreases in which of the following (a) Melting point
orders? (AIPMT 2008) (b) Electronegativity
(a) CsH > RbH > KH > NaH > LiH (c) Hydration enthalpy
(b) KH > NaH > LiH > CsH > RbH (d) Density
(c) NaH > LiH > KH > RbH > CsH 16. Which of the following will give H2 gas with dilute
(d) LiH > NaH > KH > RbH > CsH HNO3? (CPMT 2009)
9. Equimolar solution of the following were prepared in (a) Mg (b) Zn
water separately. Which one of the solutions will record (c) Cu (d) Hg
the highest pH? (AIPMT 2008)
36 s-BLOCK

17. Among the following, the least thermally stable is (c) Na2CO3.5H2O (d) Na2CO3.10H2O
(J & K CET 2009) 26. Which of the metal carbonates is decomposed on
(a) K2CO3 (b) Na2CO3 heating? (MP PMT 2010)
(c) BaCO3 (d) Li2CO3 (a) MgCO3 (b) Na2CO3
18. Correct order of stability of group IIA metal carbonates (c) K2CO3 (d) Rb2CO3
is (OJEE 2009) 27. The yellow coloured flame is of (MP PMT 2010)
(a) MgCO3 > CaCO3 > SrCO3 > BaCO3 (a) Na (b) K
(b) BaCO3 > SrCO3 > CaCO3 > MgCO3 (c) Ca (d) Ba
(c) SrCO3 > BaCO3 > CaCO3 > MgCO3 28. Among the alkali metals, cesium is the most reactive
because (RPMT 2010)
(d) CaCO3 > MgCO3 > BaCO3 > SrCO3
(a) its incomplete shell is nearest to the nucleus
19. For alkali metals, which one of the following trends is (b) it has a single electron in the valence shell.
incorrect? (KCET 2010) (c) it is the heaviest alkali metal
(a) Hydration energy : Li > Na > K > Rb (d) the outermost electron is more loosely bound than
(b) Ionisation energy : Li > Na > K > Rb the outermost electron of the other alkali metals.
(c) Density : Li > Na > K > Rb 29. The ionic mobility of alkali metal ions is aqueous
(d) Atomic size : Li < Na < K < Rb solution is maximum for (RPMT 2010)
20. Property of the alkaline earth metals that increase with + +
(a) K (b) Rb
their atomic number (AIPMT 2010)
(a) electronegativity (c) Li+ (d) Na+
(b) solubility of their hydroxides in water 30. Gypsum on heating to 390 K gives. (RPMT 2010)
(c) solubility of their sulphates in water (a) CaSO4.2H2O (b) CaSO4
(d) ionisation energy (c) CaSO4.½H2O (d) SO3 and CaO
21. Which of the following alkaline earth metal sulphates 31. Epsom salt is (RPMT 2010)
has hydration enthalpy higher than the lattice enthalpy? (a) MgSO4.7H2O (b) CaSO4.H2O
(AIPMT 2010)
(c) MgSO4.2H2O (d) BaSO4.2H2O
(a) SrSO4 (b) CaSO4
32. Molecular formula of Glauber’s salt is (JCECE 2010)
(c) BeSO4 (d) BaSO4
(a) MgSO4. 7H2O
22. The solubilites of Na2SO4, BeSO4, MgSO4 and
(b) CuSO4. 5H2O
BaSO4 will follow the order (AMU 2010)
(c) FeSO4. 7H2O
(a) BeSO4 > MgSO4 > Na2SO4 > BaSO4
(d) Na2SO4. 10H2O
(b) BeSO4 > Na2SO4 > MgSO4 > BaSO4
33. Which of the following alkaline earth metal sulphates is
(c) MgSO4 > BeSO4 > Na2SO4 > BaSO4 least soluble in water? (Haryana PET 2010)
(d) Na2SO4 > BeSO4 > MgSO4 > BaSO4 (a) BaSO4 (b) MgSO4
23. In aqueous solution, the most stable sulphate is (c) SrSO4 (d) CaSO4
(CPMT 2010) 34. Which one of the following is present an an active
(a) BeSO4 (b) MgSO4 ingredient in bleaching powder for bleaching action?
(c) CaSO4 (d) BaSO4 (AIPMT 2011)
24. The hightly reactive alkali metals are kept in (a) CaCl2 (b) CaCl2
(CPMT 2010) (c) Ca(OCl)2 (d) CaO2Cl2
(a) air (b) water 35. Which of the following compounds has the lowest
(c) kerosene (d) All of these melting point? (AIPMT 2011)
25. Washing Soda is (MP PMT 2010) (a) CaF2 (b) CaCl2
(a) Na2CO3 (b) Na2CO3.H2O
(c) CaBr2 (d) CaI2
s-BLOCK 37

36. Which one of the alkali metals forms only, the normal 44. Which of the alkali metal chloride (MCl) forms its
oxide, M2O on heating in air? (AIPMT 2012) dihyrate salt (MCl.2H2O ) easily?
(a) Rb (b) K (Odisha NEET 2019)
(c) Li (d) Na (a) LiCl (b) CsCl
37. Solubility of the alkaline earth metal sulphates in water (c) RbCl (d) KCl
decreases in the sequence (AIPMT 2015) 45. Crude sodium chloride obtained by crystallisation of
(a) Ca > Sr > Ba > Mg brine solution does not contain (Odisha NEET 2019)
(b) Sr > Ca > Mg > Ba (a) MgSO4 (b) Na2SO4
(c) Ba > Mg > Sr > Ca (c) MgCl2 (d) CaSO4
(d) Mg > Ca > Sr > Ba
46. Which of the following is an amphoteric hydroxide?
38. In context with beryllium, which one of the following
(NEET 2019)
statements is incorrect? (NEET 2016)
(a) Be(OH)2 (b) Sr(OH)2
(a) It forms Be2C.
(b) Its salts rarely hydrolyzed (c) Ca(OH2) (d) Mg(OH)2
(c) Its hydride is electron-deficient and polymeric 47. The following metal ion activates many enzymes,
(d) It is rendered passive by nitric acid. participates in the oxidation of glucose to produce ATP
39. The suspension of slaked lime in water is (NEET 2016) and with Na, is responsible for the transmission of
(a) quick lime nerve signals (NEET 2020)
(b) milk of lime. (a) Iron (b) Copper
(c) aqueous solution of slaked lime (c) Calcium (d) Potassium
(d) lime water. 48. HCl was passed through a solution of CaCl2, MgCl2
40. Ionic mobility of which of the following alkali metal and NaCl. Which of the following compound(s)
ions is lowest when aqueous solution of their salts is put crystallise(s)? (NEET 2020)
under an electric field? (NEET 2017) (a) Both MgCl2 and CaCl2
(a) K (b) Only NaCl
(b) Rb (c) Only MgCl2
(c) Li
(d) NaCl, MgCl2 and CaCl2
(d) Na
41. Among CaH2, BeH2, BaH2, the order of ionic 49. The structure of beryllium chloride in solid state and
vapour phase, are: (NEET 2021)
character is (NEET 2018)
(a) Dimer and Linear, respectively
(a) CaH2  BeH2  BaH2
(b) Chain in both
(b) BeH2  BaH2  CaH2 (c) Chain and dimer, respectively
(c) BeH2  CaH2  BaH2 (d) Linear in both
(d) BaH2  BeH2  CaH2 50. Among the following alkaline earth metal halides, one
which is covalent and soluble in organic solvents is:
42. Which of the following oxides is most acidic in nature?
(NEET 2021)
(NEET 2018)
(a) Magnesium chloride (b) Beryllium chloride
(a) BeO (b) BaO
(c) Calcium chloride (d) Strontium chloride
(c) MgO (d) CaO
43. Magnesium reacts with an element (X) to form an ionic
compound. If the ground state electronic configuration
of (X) is 1s2 2s2 2p3, the simplest formula for this
compound is (NEET 2018)
(a) MgX2 (b) Mg2X
(c) Mg2X3 (d) Mg3X2
38 s-BLOCK

EXERCISE – 3: Achiever’s Section

Single Answer Type Questions
1. Among the following element the non-radioactive (a) Li+>K+>Na+>Rb+>Cs+
elements(s) is/are (b) Li+>Na+>K+>Rb+>Cs+
(a) Francium (b) Radium (c) Li+>Na+>K+>Rb+>Cs+
(c) Both (a) and (b) (d) None of these (d) Li+>Na+>Rb+>K+>Cs+
2. Which of the following statements(s) is/are incorrect 9. The most correct reason for colour of alkali metal ions
regarding the s-block elements? is
I. Francium is highly radioactive element. (a) Presence of single valence electron
II. Oxides and hydroxides of alkali metals and (b) Excitation of valence electron
alkaline earth metals are not alkaline in nature. (c) Emission of radiation in visible region during come
III. Sodium and potassium are the only two s-block back of electron to the ground state energy level
elements are found in large proportion in biological (d) None of the above
fluids. 10. The colour of alkali metal ions in any sample can be
IV. Biological function of s-block elements is due to detected by
maintenance of ion balance and nerve impulse (a) Flame photometry
condition. (b) Atomic adsorption method
(a) Only I (b) II and III (c) Both (a) and (b)
(c) II and III (d) Only III (d) None of the above
3. Which of the following is/are correct pair(s) regarding 11. What will be the oxidation state of nitrogen and alkali
diagonally related elements? metal when the nitrogen and alkali metal react with
(a) Beryllium and aluminium each other?
(b) Lithium and magnesium (a) -3 and +1 (b) -1 and +1
(c) Sodium and aluminium (c) -1 and -1 (d) -3 and -1
(d) Both (a) and (b) 12. In concentrated solution, the colour of alkali metals in
4. Which of the following ion(s) is/are responsible for liquid ammonia is
biological functions such as maintenance of ion balance (a) Blue (b) Bronze
and nerve impulse conduction? (c) Colourless (d) Red
(a) Sodium (b) Potassium 13. Which of the following statement(s) is/are incorrect
(c) Magnesium (d) All of these regarding property of alkali metals?
5. Alkali metals are never found in free state because I. Alkali metal on reaction with water produces a gas
(a) They have one valence electron as a byproduct which burns with poping sound.
(b) They form monovalent ion very easily II. Alkali metals dissolve in excess of ammonia to
(c) Thy lose one electron very easily produce bronze colour liquid.
(d) All of the above III. Alkali metal halides are ionic in nature.
6. The hydration enthalpies of alkali metal ions …A… IV. All alkali metal hydrides are ionic in nature.
with increase in ionic sizes. Here, A refer to (a) I, II and III (b) Only I
(a) Increases (b) Decreases (c) II and IV (d) Only IV
(c) Remain unchanged (d) None of the above 14. The most electropositive alkali metal is
7. Which of the following has the lowest value of (a) Na (b) K
hydration enthalpy? (c) Rb (d) Cs
(a) Na+ (b) K+ 15. Which of he following is/are less soluble in water?
+
(c) Li (d) Cs+ LiF, CsI, NaCl, KCl
8. On moving top to bottom among a group the correct (a) Lic, NaCl (b) Csl, LiF
trend of hydration enthalpies for alkali metal ions is (c) KCl, NaCl (d) CsF, NaCl
s-BLOCK 39

16. Hydrogen carbonate of lithium doesn’t exist in solid 23. Which of the following order is correct regarding
state due to electropositive character of alkaline earth metals?
(a) Low polarization value of Li+ (a) Be < Mg >Ca <Sr <Ra
(b) Low hydration energy of Li+ (b) Be > Mg >Ca >Sr >Ra
(c) High hydration energy of Li+ (c) Be < Mg <Ca <Sr <Ra
(d) High polarization value of Li+ (d) None of the above
17. On moving top to bottom the negative value of 24. Assertion (A): Ba, Ca and Sr produces individual
formation …A… for fluoride of alkali metals. Here, A characteristic colour to flame test.
refer to Reason (R): this is due to excitation of loosely held
electrons from outermost orbit to excited state of
(a) Becomes less negative
orbital.
(b) Becomes more negative (a) Both A and R are correct; R is the correct
(c) Remains constant explanation of A
(d) None of the above (b) Both A and R are correct; R is not the correct
18. Why lithium compound are soluble in organic solvent? explanation of A
Charge (c) A is correct; R is incorrect
(a) Due to small ratio (d) R is correct; A is incorrect
Radius 25. Property of the alkaline earth metals that increases with
Charge their atomic number
(b) Due to its large ratio (a) Solubility of their hydroxides in water
Radius
(c) Due to its high polarization (b) Solubility of their sulphates in water
(d) Both (b) and (c) (c) Ionization energy
19. Which of the following metal do not form salt with (d) Electronegativity
ethyne? 26. A chemical (A) is used for the preparation of washing
(a) Li (b) Na soda to recover ammonia. When CO2 is bubbled
(c) K (d) Cs through an aqueous solution of A, the solution turns
20. [X] and [Y] are two nitrates of alkali metals [X] and milky. It is used white washing due to disinfectant
[Y] on decomposition produces oxides and nitrites nature. What is the chemical formula of (A)?
respectively. Here, [X] and [Y] refer to (a) Ca(HCO3)2 (b) CaO
(a) LiNO3 and KNO3 (b) LiNO3 and LiNO3 (c) Ca(OH)2 (d) CaCO3
(c) KNO3 and LiNO3 (d) None of these 27. Chemical clinker can be obtained by the reaction of
21. Along the group atomic and ionic radii are …X… and (a) Clay and lime (b) Lime and gypsum
along the period atomic and ionic radii are …Y… Here, (c) Clay and Fe2O3 (d) All of these
X and Y refer to 28. ‘A’ is an important constituent of cement which is
(a) Increases and decreases responsible for setting of cement. What is the number
(b) Decreases and increases of water of crystallization present in ‘A’?
(c) Decreases and decreases (a) 2 (b) 1
(d) Remain in constant and decreases (c) 0 (d) ½
22. The correct reason for smaller size of alkaline earth 29. Choose the incorrect statement among the following.
metal than that of alkali metal is that (a) Calcium present in bone is soluble
(a) Alkali metals have high value of nuclear charge (b) Calcium present in bone is redeposited
than alkaline earth metal (c) Calcium present in bone in inert
(b) Alkali metal have low value of nuclear charge than (d) Both (a) and (b) are incorrect
alkaline earth metal 30. Which one of the following has magnesium?
(c) Alkali metal has high value of screening constant (a) Vitamin B12 (b) Chlorophyll
than alkaline earth metals (c) Haemocyanin (d) Carbonic anhydrase
(d) Both (a) and (c)
40 s-BLOCK

Notes:

Find Answer Key and Detailed Solutions at the end of this book
:

s-Block
 p - BLOCK
(GROUP 13 AND 14)

LearnLIVEOnline __________
Chapter 14

p-Block (Group 13 And 14)

1. Introduction presence of additional 10 d-electrons offer only poor screening

effect for the outer electrons from the increased nuclear charge in
The p–block contains metals, metalloids as well as non–metals. gallium. Consequently, the atomic redius of gallium (135 pm) is
The p–block elements have general valence shell electronic less than that of aluminium (143 pm).
configuration ns2 np1–6. The first member of each group from
13–17 of the p–block elements differ in many respects from the 1.3 Ionization Enthalpy
other members of their respective groups because of small size, The ionisation enthalpy values as expected from the general trends
high electronegativity and absence of d–orbitals. The first member do not decrease smoothly down the group . The decreases from B
of a gorup also has greater ability to form p–p multiple bonds to to Al is associated with increases in size. The observed disconti-
itself (e.g. C = C, C  C, N  N) and to element of second row nuity in the ionisation enthalpy values between Al and Ga, and
(e.g C = O, C = N, C  N, N = O) compared to the other members of between In and Tl are due to inability of d- and f electrons.
the same group. The highest oxidation of p–block element is equal 1.4 Electronegativity
to the group number minus 10. Moving down the group, the
Down the group, electronegativity first decreases from B to Al
oxidation state two less than the highest group oxidation state
and then increases marginally. This is because of the discrepan-
becomes more stable in groups 13 to 16 due to inert pair effect.
cies in atomic size of the elements.
Group 13 Elements : The Boron Family
Boron is a typical non-metal, aluminium is a metal and gallium,
1.5 Melting and Boiling Points
indium and thallium are almost exclusively metallic in character, Melting Point B > Al > Tl > In > Ga
Boiling Point B > Al > Ga > In > Tl

1.1 Electronic Configuration 2. Physical Properties

The outer electronic configuration of these elements is ns2 np1. Boron is non-metallic in nature . It is extremely hard and black
coloured solid. It exists in many allotropic forms. Due to very
1.2 Atomic Radii strong crystalline lattice, boron has unusually high melting point.
On moving down the group, for each successive member one Gallium with low melting point (303 K), could exist in liquid state
extra shell of electrons is added and therefore, atomic radius is during summer.
expected to increases. Atomic radius of Ga is less than of Al. The

Table 14.1: Atomic & Physical Properties

Element B Al Ga In Tl
Atomic Number 5 13 31 49 81
Atomic Mass 10.81 26.98 69.72 114.82 204.38
Electronic configuration [He]2s 2p 2 1
[Ne]3s 3p
2 1
[Ar]3d 4s 4p
10 2 1
[Kr]4d 5s 5p
10 2 1
[Xe]4f145d106s26p1
Atomic Radius/pm 85 143 135 167 170
Ionic Radius M3+/pm – 53.5 62 80 88.5
Ionization enthalpy I 800 577 578 558 590
/(kJ mol )
–1
II 2427 1816 1979 1820 1971
III 3659 2744 2962 2704 2877
Electronegativity 2.0 1.5 1.6 1.7 1.8
Density/[g cm-3 (293 K)] 2.35 2.70 5.90 7.31 11.85
Melting point / K 2453 933 303 430 576
Boiling point / K 3923 2740 2676 2353 1730

SCAN CODE
p-Block (Group 13 and 14)
p-BLOCK (GROUP 13 AND 14) 43

3. Chemical Properties
3.1 Reactivity Towards Air
Boron is unreactive in crystalline form. Aluminium forms a very
thin oxide layer on the surface which protects the metal from
Fig.14.1: Dimer of AlCl3
further attack. Amorphous boron and aluminium metal on heating
in air form B2O3 and Al2O3 respectively. With dinitrogen at high
temperature they form nitrides.

5. Compouns of Boron
2E(s) + 3 O2 (g)  2 E2O3(s)

2E(s) + N2(g)  2 EN (s).
5.1 Orthoboric Acid (H3BO3)
Boron trioxide is acidic and reacts with base. Aluminium and gal- 5.1. 1 Preparation
lium oxides are amphoteric and indium and thallium are basic. It is precipitated by treating a concentrated solution of borax with
sulphuric acid.
Na2B4O7 + H2SO4 + 5H2O  Na2SO4 + 4H3BO3 
3.2 Reactivity Towards Acids and Alkalies
5.1. 2 Properties
Boron does not react with acids and alkalies even at moderate
It is a weak monobasic acid and in aqueous solution. The boron
temperature; but aluminium dissolves in mineral acids and aque-
atom completes its octet by removing OH– from water molecules:
ous alkalies and thus shows amphoteric character.
B(OH)3(aq) + 2H2O()  B(OH)4– (aq) + H3O+(aq).
Aluminimum dissolved in dilute HCl and liberates dihydrogen.
However, concentrated nitric acid renders aluminium passive by It, therefore, functions as a Lewis acid and not as a proton donor.
forming protective oxide layer on the surface . Aluminium also When heated it first forms metaboric acid (HBO2) and then boron
reacts with aqueous alkali and liberates dihydrogen . trioxide.
2 Al(s) + 6 HCl(aq)  2 Al3+ (aq) + 6 Cl–(aq) + 3 H2(g) 
H 3 BO 3  HBO 2 
 B2 O3
2Al(s) + 2NaOH (aq) + 6H2O (1)  2Na [Al(OH)4] (aq) + 3H2(g)
+ – Metaboric acid Boron trioxide

Sodium tetrahydroxoaluminate (III) Orthoboric acid is greasy to touch less soluble in cold water but
more soluble in hot water. It has a layered structure in which
planar BO3 units are joined by hydrogen bonds.
3.3 Reactivity Towards Halogens
These elements react with halogen to form trihalides
(except Tl I3 )..
2E(s) + 3X2 (g)  2EX3 (s) (X = F, Cl Br, I)
The tri-chlordes, bromides and iodies of all these elements being
covalent in nature are hydrolysed in water. Species like tetrahe-
dral [M(OH)4]– and octahedral [M(H2O)6]3+ (except in boron) exist
in aqueous medium.
The monomeric trihalides, being electron deficient, are strong
Lewis acids.

4. Anomalous Property of Boron Fig.14.2: Structure of Boric Acid (Dotted line represent
hydrogen bonds)
It is due to the absence of d orbitals that the maximum covalency
of B is 4. Since the d orbitals are available with Al and other
5.1.3 USES
elements, the maximum covalence can be expected beyond 4.
It is an antiseptic and its water solution is used as an eyewash.
Thus, boron hallides do not dimerise like other elements which
It is also used in glass, enamel and pottery industry.
can form halogen bridged molecules. (Dimer of AlCl3 has 3 centre
- 4 electrone bond)

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p-Block (Group 13 and s14)
44 p-BLOCK (GROUP 13 AND 14)

5.2 Borax (Na2B4O7.10H2O) Borax-bead test: Boric anhydride reacts with certain metal salts
such as, Ni2+, Co2+, Cr3+, Cu2+, Mn2+ etc. to form coloured
5.2.1 Preparation metaborates. The colour of the metaborates can be used to iden-
It is found in nature but can also be prepared by the following tify the metallic ions (cations) in salts.
methods. 
Na2B4O7. 10H2O  740ºC
Na2B4O7  2NaBO2+B2O3
(i) From Colemanite. 10H2O

When colemanite powder is heated with Na2CO3 solution, Borax bead

the following reaction occurs with the precipitation of CuO + B2O3  Cu(BO2)2 (blue bead)
CaCO3. 5.2.3 Uses
Ca2B6O11 + 2Na2CO3  2CaCO3  + Na2B4O7 + (i) In borax bead test
2NaBO2 (ii) In purifying gold
The filterate is cooled when white crystals of borax are (iii) As flux during welding of metals.
precipitated. The mother liquor on treatment with CO2
converts NaBO2 to Na2B4O7 which precipitates out on
crystallization. 5.3 Diborane (B2H6)
4NaBO2 + CO2  Na2B4O7 + Na2CO3 Binary compounds of B with H are called boron hydrides or
(ii) From orthoboric acid. boranes.
Borax is obtained by the action of Na2CO3 on orthoboric
acid.
4H3BO3 + Na2CO3  Na2B4O7 + 6H2O + CO2 

Fig.14.3: Structure of B2H6

5.3. 1 Preparation
(i) ether
4BF3 + 3LiAlH4   2B2H6 + 3LiF + 3AlF3
5.2. 2 Properties silent electric
(i) Borax is a white powder, less soluble in cold water, more (ii) 2BCl3 + 6H2 (excess) 
discharge
 B H + 6HCl
2 6
soluble in hot water.
(ii) Its aqueous solution is alkaline because of its hydrolysis to ether
(iii) 8BF3 + 6LiH   B2H6 + 6LiBF4
weak acid H3BO3 and strong alkali NaOH.
ether B2H6 + 2Na + H2 (Convenient lab
(iv) 2NaBH4 + 2 
Na2B4O7 + 7H2O  4H3BO3 + 2NaOH
method)
(iii) Action of heat.
When borax powder is heated, it first swells due to loss of ether
(v) 3NaBH4 + 4BF3 
450 K 3NaBF4 + 2B2H6 (Industrial
water in the form of steam but at 740oC it becomes converted
into colourless transparent borax bead. method)
 5.3. 2 Properties
Na2B4O7.10H2O  Na2B4O7 + 10 H2O
740ºC  2NaBO + B O (borax bead) (i) Diborane is a colourless gas.
Na2B4O7  2 2 3
(ii) It is rapidly decomposed by water with the formation of
(iv) Action of acids : H3BO3 & H2
Na2B4O7 + 2HCl + 5H2O  2NaCl + 4H3BO3 (boric acid) B2H6 + 6H2O  2H3BO3 + 6H2
Correct formula of borax is Na2[B4O5(OH)4] . 8H2O (iii) Mixtures of diborane with air or oxygen catches fire
spontaneously producing large amount of heat. Diborane

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p-Block (Group 13 and 14)
p-BLOCK (GROUP 13 AND 14) 45
has a higher heat of combustion per unit weight of fuel than
most other fuels. It is therefore used as a rocket fuel. Al 2 O 3  2NaOH  aq  
Aluminium oxide Sodium hydroxide
B2H6 + 3O2  B2O3 + 3H2O H = – 1976 kJ mol–1
2NaAlO 2  aq   H 2 O  l 
(iv) Cleavage reactions
Sodium aluminate
(a) B2H6 + 2Me3N  2Me3NBH3
200ºC, 20atm 2BH CO 6.1.3 Uses
(b) B2H6 + 2CO   3
(i) For the extraction of aluminium.
Heat (ii) For making artificial gems.
(v) 3B2H6 + 6NH3 [BH2(NH3)2]+ [BH4]–  2 B3N3H6
+ 12H2 (iii) For the preparation of compounds of aluminium.
In above reaction B3N3H6 is formed it is known borazine (iv) In making furnace linings. It is a refractory material.
(inorganic benzene) (v) As a catalyst in organic reactions.

7. Introduction: Group 14
Elements
Carbon (C), silicon (Si), germanium (Ge), tin (Sn) and lead (Pb) are
the members of group 14. Naturally occurring carbon contains
two stable isotopes:12C and 13C. In addition to these third iso-
topes, 14C is also presents , it is a radioactive isotope with half-
life 5770 years and used for radiocarbon dating. Silicon is a very
important component of ceramices, glass and cement. Germanium
Excess NH exists only in traces. Tin occurs mainly as cassiterite, SnO2 and
nB2 H 6  3   BN  n
(vi) High temperature lead as galena, PbS. Ultrapure form of germanium and silicon are
Diboane Boron nitride
used to make transistors and semiconductor devices.
Born nitride is known as inorganic graphite.
7.1 Electronic Configuration
The valence shell electronic configuration of these elements is
6. Compouns of Aluminium (Al) ns2 np2.
6.1 Aluminium Oxide (Al2O3) 7.2 Covalent Radius
It is also called alumina. It occurs in nature in the form of bauxite There is a considerable increase in covalent radius from C to Si,
and corundum. It is also found in the form of gems. thereafter from Si to Pb a small increase in radius is observed.
6.1.1 Preparation This is due to the presence of completey filled d and f orbitals in
heavier members.
Pure Al2O3 is obtained by igniting Al2(SO4)3, Al(OH)3 or
ammonium alum. 7.3 Ionization Enthalpy
 Al O + 3SO  The first ionization enthalpy of group 14 members is higher than
Al2(SO4)3  2 3 3
the corresponding members of group 13. The influence of inner
 Al O + 3H O
2Al(OH)3  core electron is visible here also. In general the ionisation en-
2 3 2
thalpy decreases down the group.Small decreases in iH from Si
6.1. 2 Properties to Ge to Sn and slight increase in iH from Sn to Pb is the conse-
It is a white amorphous powder insoluble in water but soluble in quence of poor shielding effects of intervening d and f–orbitals
acids (forming eg., AlCl3) as well as alkalies (forming NaAlO2) , and increases in size of the atom.
Thus amphoteric in nature. It is a polar covalent compound. 7.4 Electronegativity
Al2 O3  s   6HCl  aq   Due to small size, the elements of this group are slightly more
Aluminium oxide Hydrochloric acid electronegative than group 13 elements. The electronegativity
value for elements from Si to Pb are almost the same.
2AlCl3  aq   3H 2 O  l 
Aluminium chloride

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p-Block (Group 13 and 14)
46 p-BLOCK (GROUP 13 AND 14)

8. Physical Properties als with low melting points. Melting points and boiling points of
group 14 elements are much higher than those of corresponding
All group 14 members are solids. Carbon and silicon are non- elements of group 13.
metals, germanium is metalloid whereas tin and lead are soft met-

Table 14.2:Atomic & Physical Properties

Element C Si Ge Sn Pb
Atomic Number 6 14 32 50 82
Atomic Mass 12.01 28.09 72.60 118.71 207.2
Electronic configuration [He]2s 2p 2 2
[Ne]3s 3p
2 2
[Ar]3d 4s 4p
10 2 2
[Kr]4d 5s 5p
10 2 2
[Xe]4f145d106s26p2
Atomic Radius/pm 77 118 122 140 146
Ionic Radius M /pm+4
– 40 53 69 78
Ionization enthalpy I 1086 786 761 708 715
/(kJ mol–1) II 2352 1577 1537 11411 1450
III 4620 3228 3300 2942 3081
Electronegativity 2.5 1.8 1.8 1.8 1.9
Melting point / K 4373 1693 1218 505 600
Boiling point / K – 3550 3123 2896 2024

9. Chemical Properties 9.2 Reactivity Towards Water

Oxidation State: Carbon , silicon and germanium are not affected by water . Tin
The group 14 elements have four electrons in outermost shell. decomposes steam to form dioxide and dihydrogen gas. Lead is
The common oxidation states exhibited by these elements are + 4 unaffected by water, probably becauses of a protective oxide film
and + 2. Carbon also exhibits negative oxidation states.Since the formation.
sum of the first four ionization enthalpies is very high, compound   SnO + 2H
Sn + 2H2O  2 2
in +4 oxidation state are generally covalent in nature. In heavier
members the tendency to show +2 oxidation state increases in the 9.3 Reactivity Towards Halogen
sequence Ge < Sn < Pb. It is due to the inability of ns2 electrons of Except carbon, all other members react directly with halogen un-
valence shell to participate in bonding. (due to inert pair effects)
der suitable condition to make halides.
Table 14.4 Halides of Group 14 Elements
9.1 Reactivity Towards Oxygen
All members when heated in oxygen form oxides. There are mainly Dihalides (MX2) Tetrahalides (MX4)
two types of oxides. Heavier members Ge to Pb are All elements can form
Table 14.3: Monoxides and Dioxides of Group 14 able to make halides of formula tetrahalides. However, Pb
MX2. doesn’t form Pbl4 because Pb –
Elements
I bond initially formed during
Monoxides (MO) Dioxides (MO2) the reaction does not release
SiO only exists at high CO2, SiO2, and GeO2 - acidic enough energy to unpair and
temperature. excite 6s2 electrons.
CO - neutral SnO2 and PbO2 - amphoteric
Stability of dihalides increases Stability decreases down the
GeO - distinctly acidic group.
down the group.
SnO and PbO - amphoteric
PbX > PbX GeX2 < GeX4
2 4

MX2 is more ionic than MX4 Most of the MX4 are covalent
Oxides in higher oxidation states of elements are generally more
in nature except SnF4 and PbF4.
acidic than those in lower oxidation states.

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p-Block (Group 13 and 14)
p-BLOCK (GROUP 13 AND 14) 47

Except CCl4, other tetrachlorides are easily hydrolysed by water

because the central atom can accommodate the lone pair of elec-
trons from oxygen atom of water molecule in d orbital.

10. Important Trends and

Anomalous Behaviour of
Carbon
Carbon also differs from rest of the members of its group. It is due
to its smaller size, higher electronegativity, higher ionisation en-
thalpy and unavailability of d orbitals.
Carbon atoms have the tendency to link with one another through Fig.14.4: Structure of Diamond
covalent bonds to form chains and rings. This property is called 11.2 Graphite
catenation. This is becauses C–C bonds are very strong. Down Graphite has layered structure. Layers are held by van der Waal’s
the group the size increases tendency to show catenation de- forces and distance between two layers is 340 pm. Each layer is
creases. The order of catenation is C > > Si > Ge  Sn. Lead does composed of planar hexagonal rings of carbon atoms. C – C bond
not show catenation. length within the layer is 141.5 pm Each carbon atom in hexagonal
Table 14.5: Bond Enthalpy Value ring undergoes sp2 hybridisation and make three sigma bonds
with three neighbouring carbon atoms. Fourth electron forms a 
Bond Bond enthalpy / kJ mol–1 bond. The electrons are delocalised over the whole sheet. Elec-
C—C 348 trons are mobile and, therefore graphite conducts electricity along
Si — Si 297 the sheet.
Ge — Ge 260
Sn — Sn 240

11. Allotropes of Carbon

Carbon exhibits many allotropic forms; both crystallic as well as
amorphous.

11.1 Diamond
It has a crystalline lattice. In diamond each carbon atom under-
goes sp3 hybridisation and linked to four other carbon atoms by
using hybridised orbitals in tetrahedral fashion. The C–C bond
length is 154 pm. The structure extends in space and produces a
rigid three dimensional network of carbon atoms .In this structure
directional covalent bonds are presents throughout the lattice.
It is very difficult to break extended covalent bonding and there-
fore, diamond is a hardest substance on the earth.

Fig.14.5: Structure of Graphite

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p-Block (Group 13 and 14)
48 p-BLOCK (GROUP 13 AND 14)

11.3 Fullerenes
Fullerenes are made by the heating of graphite in an electrical arc 12. Compounds of Carbon
in the presence of inert gases such as helium or argon. Fullerences
are the only pure form of carbon becauses they have smooth
12.1 Oxides of Carbon
structure without having ‘dangling’ bonds. Fulleren are cage like 12.1.1 Carbon dioxide (CO2)
molecules. C60 molecule has a shape like soccer ball and called 12.1.1.1 Preparation
Buckminsterfullerene.
(i) In the laboratory it can be conveniently made by the action
It contains twenty six -membered rings and twelve five membered of dilute hydrochloric acid on marble chips:
rings. A six membered ring is fused with six or five membered rings
CO32-(aq) + 2H+(aq)  CO2(g) + H2O(l)
but a five membered ring can only fuse with six membered rings.
(ii) Industrially it is produced as a by-product during the
All the carbon atoms are equal and they undergo sp2 hybridisation.
Each carbon atom forms three sigma bonds with other three car- manufacture of quicklime and in fermentation processes:
bon atoms. The remaining electron at each carbon atom is CaCO3(s)  CaO(s) + CO2(g)
delocalised in molecular orbitals, which in turn give aromatic char-
acter to molecule. This ball shaped molecule has 60 vertices and 12.1.1.2 Properties
each one is occupied by one carbon atom and it also contains
(i) It is a colourless, odourless and heavy gas which dissolves
both single and double bonds with C – C distance of 143.5 pm and
in its own volume of water at ordinary temperature and
138.3 pm respectively. Spherical fullerenes are also called bucky
pressure. Like all gases, it dissolves much more readily in
balls in short. It is very important to know that graphite is thermo-
water when the pressure is increased and this principle is
dynamically most stable allotrope of carbon.
used in the manufacture of soda water and fizzy drinks.
(ii) CO2 is easily liquefied (critical temperature = 31.1oC)
(iii) Carbon dioxide readily reacts with alkalies forming the
carbonate and, if CO2 is in excess, the hydrogen carbonate.
This is the basis of the lime-water test for CO2 gas.
Ca(OH)2(aq) + CO2(g)  CaCO3(s) + H2O(liq)
CaCO3(s) + H2O(liq) + CO2(g)  Ca(HCO3)2(aq)
The above reaction accounts for the formation of temporarily
hard water.
(iv) Carbon dioxide, which is normally present to the extent of ~
0.03% by volume in the atmosphere, is removed from it by
the process known as photosynthesis. It is the process by
Fig.14.6: Structure of Fullerene
which green plants convert atmospheric CO 2 into
Uses of Carbons
carbohydrates such as glucose. The overall chemical change
(i) Graphite fibres embedded in plastic material form high can be expressed as:
strength, lightweight composites. The composites are used
in products such as tennis rackets, fishing rods, aircrafts hv
6 CO2 + 12 H2O  
Chlorphyll C6H12O6 + 6 O2 + 6 H2O
and canoes.
(ii) Graphite is used for electrodes in batteries and industrial By this process plants make food for themselves as well as
electrolysis. for animals and human beings.But the increase in
(iii) Crucibles made from graphite are inert to dilute acids and combustion of fossil fuels and decomposition of limestone
alkalies. for cement manufacture in recent years seem to increase
the CO2 content of the atmosphere. This may lead to increase
(iv) Carbon black is used as black pigment in black ink and as
in green house effect and thus, raise the temperature of the
filler in automobile tyres.
atmosphere which might have serious consequences.
(v) Coke is used as a fuel and largely as a reducing agent in
(v) Gaseous CO2 is extensively used to carbonate soft drinks.
metallurgy.
Being heavy and non–supporter of combustion it is used
as fire extinguisher. A substantial amount of CO2 is used to

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p-Block (Group 13 and 14)
p-BLOCK (GROUP 13 AND 14) 49

manufacture urea. with haemoglobin, which is about 300 times more stable
(vi) Carbonic acid, which is a weak dibasic acid and ionises in to than the oxygen-haemoglobin complex. This prevents
steps as follows: haemoglobin in the red blood corpuscles from carrying
oxygen round the body and ultimately resulting in death
H 2 CO3  aq   H 2 O  l   HCO3–  aq   H3 O   aq  (ii) Carbon monoxide is a powerful reducing agent, being
HCO3–  aq   H 2 O  l   CO32–  aq   H 3 O  aq  employed industrially in the extraction of iron and nickel:

H2CO3/HCO3– buffer system helps to maintain pH of blood Fe2O3(s) + 3CO(g)  2Fe(s) + 2CO2(g)
between 7.26 to 7.42
NiO(s) + CO(g)  Ni(s) + CO2(g)
(iii) It reacts with many transition metals, forming volatile
12.1.2 Carbon Monoxide (CO) carbonyls; the formation of nickel carbonyl followed by its
12.1.2.1 Preparation decomposition is the basis of the Mond’s process for
(i) It forms together with CO2, when carbon or carbonaceous obtaining very pure nickel:
matter is oxidized by air or oxygen. It is also produced when 90ºC Ni(CO) (liq)
Ni(s) + 4CO(g)  4
CO2 is reduced by red- hot carbon; this reaction is of
importance in metal extractions. 180ºC  Ni(s) + 4CO(g)
Ni(CO)4(liq) 
C(s) + CO2(g)  2CO(g)
(ii) In the laboratory it can be prepared by dehydrating
12.1.3 Carbon suboxide (C3O2)
methanoic acid with concentrated sulphuric acid:
This is an evil-smelling gas and can be made by dehydrating
373K propanedioic acid (malonic acid), of which it is the anhydride,
 
HCOOH (liq) conc.H SO CO(g) + H2O with phosphorus pentoxide:
2 4
3 CH2(COOH)2 + P4O10  3C3O2 + 4H3PO4
(iii) If oxalic acid is dehydrated in the same way, CO2 is formed
as well. When heated to about 200oC, it decomposes into CO2 and C:
C3O2(g)  CO2(g) + 2C(s)
conc. H SO , 
2 4 
H2C2O4  CO + CO2 The molecule is thought to have a linear structure:
–H O 2 O=C=C=C=O
(iv) On commercial scale it is prepared by the passage of steam –2 + 2 0 + 2 – 2 (Oxidation state of each atom)
over hot coke. The mixture of CO and H2 thus produced is
known as water gas or synthesis gas.
13. Compounds of Silicon
4731273 K CO (g) + H (g) (water gas).
C (s) + H2O (g)   2
13.1 Silicon Dioxide SiO2
When air is used instead of steam, a mixture of CO and N2 is
Silicon dioxide, commonly known as silica, occurs in several
produced, which is called producer gas.
crystallographic forms. Quartz, cristobalite and tridymite are some
1273 K of the crystalline forms of silica, and they are interconvertable at
2 C (s) + O2 (g) + 4 N2 (g)    2 CO (g) + 4 N2 (g)
(Producer gas). suitable temperature. Silicon dioxide is a covalent, three-dimen-
sional network solid in which each silicon atom is covalently
Water gas and producer gas are very important industrial
bonded in a tetrahedral manner to four oxygen atoms.
fuels. Carbon monoxide in water gas or producer gas can
Each oxygen atom in turn covalently bonded to another silicon
undergo further combustion forming carbon dioxide with
atoms. Each corner is shared with another tetrahedron. The entire
the liberation of heat.
crystal may be considered as giant molecule in which eight mem-
(v) Zn + CO2  ZnO + CO bered rings are formed with alternates silicon and oxygen atoms.
Silica in its normal form is almost non-reactive because of very
12.1.2.2 Properties high Si – O bond enthalpy. It resists the attack by halogens,
(i) Carbon monoxide is a colourless, odourless gas which burns dihydrogen and most of the acids and metals even at elevated
in air with a blue flame, forming CO2. The highly poisonous temperatures. Howevers it is attacked by HF and NaOH.
nature of CO arises because of its ability to form a complex SiO2 + 2 NaOH  Na2SiO3 + H2O

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p-Block (Group 13 and 14)
50 p-BLOCK (GROUP 13 AND 14)
SiO2 + 4 HF  SiF4 + 2 H2O (ii) Pyrosilicate
In these silicates two tetrahedral units are joined by sharing oxygen
at one corner thereby giving [Si2O7]6– units.

Fig.14.7: Structure of Silicon Dioxide

Fig.14.9: Structure of Pyrosilicates

Quartz is extensively used as a piezoelectric material ; it has made (–) charge will be present on the oxygen atoms which is bonded
possible to develop extremely accurate clocks, modern radio and with one Si atom.
television broadcasting and mobile radio communications. Silica (iii) Cyclic silicates
gel used as a drying agent and as a support for chromatographic
If two oxygen atoms per tetrahedron are shared to form closed
materials.
rings such that the structure with general formula (SiO32–)n or
(SiO3)n2n– is obtained, the silicates containing these anions are
called cyclic silicates.
13.2 Silicates
Si3O96– and Si6O1812– anions are the typical examples of cyclic
A large number of silicates minerals exist in nature. Some of the
silicates.
examples are - Feldspar, Zeolites and Mica
The basic structural unit of silicates is SiO44– in which silicon
atom is bonded to four oxygen atoms in tetrahedral fashion.
In silicates either the discrete unit is present or a number of such
units are joined together via corners by sharing 1, 2, 3 or 4 oxygen
atoms per silicate units.
When silicate units are linked together, they form chain, ring,
sheet or three-dimensional structures.
Negative charge on silicate structure is neutralised by positively
charged metal ions.
13.2.1 Classification of Silicates
(i) Orthosilicates
These contain discrete [SiO4]4– units i.e., there is no sharing of
Fig.14.10 : Structure of Cyclic silicates
corners with one another as shown is figure.
(iv) Chain silicates
Chain silicates may be further classified into simple chain & double
chain compounds.
In case of simple chains two corners of each tetrahedron are shared
& they form a long chain of tetrahedron. Their general formula is
also same as the cyclic silicates i.e. (SiO3)n2n–

Fig.14.8: Structure of Orthosilicates

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p-BLOCK (GROUP 13 AND 14) 51

13.3 Silicones
These are a group of organosilicon polymers, which have (R2SiO)
as a repeating unit.
The starting materials for the manufacture of silicones are alkyl or
aryl substituted silicon chlorides, RnSiCl(4–n), where R is alkyl or
aryl group.

Fig.14.11 : Structure of Chain silicates

Similarly, double chain silicates can be drawn in which two simple

chains are joined together by shared oxygen. Such compounds
are also known as amphiboles.
The silicones are formed by the hydrolysis of alkyl or aryl
substituted chlorosilanes and their subsequent polymerisation.
The alkyl or aryl substituted chlorosilanes are prepared by the
following reactions.
Cu 
(a) RCl + Si  R SiCl + R2SiCl2 + RSiCl3+R4Si
300ºC 3

(b) RMgCl + SiCl4  RSiCl3 + MgCl2

2RMgCl + SiCl4  R2SiCl2 + 2MgCl2
3RMgCl + SiCl4  R3SiCl + 3MgCl2
After fractional distillation, the silane derivatives are hydrolysed
and the ‘hydroxides’ immediately condense by intermolecular
(v) Sheet Silicates elimination of water. The final product depends upon the number
When SiO4 unit share 3 corners the structure formed is an infinite of hydroxyl groups originally bonded to the silicon atom:
two dimension sheet structure with general formula (Si2O5)n2n–

In this manner several molcules may combine to form a long chain

Si 2 O5 n
2n 
sheet polymer whose both the ends will be occupied by –OH groups.
Such compounds are generally represented from the following
Fig.14.12 :Structure of Sheet Silicates
formula.
(vi) Three dimenstional sheet silicates :
These silicates involve all four oxygen atom in sharing with
adjacent SiO44– tetrahedral units. e.g. Quartz.

SCAN CODE
p-Block (Group 13 and 14)
52 p-BLOCK (GROUP 13 AND 14)

The dichloro derivative will form a long chain polymer as usual.

But the growth of this polymer can be blocked at any stage by
the hydrolysis product of mono-chloro derivative.

The polymer chain depicted above is terminated by incorporating

a small quantity of the monochlorosilane derivative into the
hydrolysis mixture.
Silicones can be prepared from the following types of compounds
only.
Silicones being surrounded by non-polar alkyl groups are water
(i) R3SiCl (ii) R2SiCl2 (iii) RSiCl3
repelling in nature. They have in general high thermal stability,
Silicones from the hydrolysis of (CH3)3 SiCl high dielectric strength and resistance to oxidation and chemicals.
H 2 O (CH ) Si (OH)
(CH3)3 SiCl  They have wide applications. They are used as sealant, greases,
 3 3
electrical insulators and for water proofing of fabrics. Being
biocompatible they are also used in surgical and cosmetic plants.

13.4 Zeolites
If aluminium atoms replace few silicon atoms in three-dimensional
network of silicon dioxide, overall structure known as
aluminosilicate, acquires a negative charge. Cations such as
Na+, K+ or Ca2+ balance the negative charge. Examples are feldspar
and zeolites.
Zeolites are widely used as a catalyst in petrochemical industries
for cracking of hydrocarbons and isomerisation, e.g., ZSM-5
Silicones from the hydrolysis of a mixture of (CH3)3 SiCl & (CH3)2 (A type of zeolite) used to convert alcohols directly into gasoline.
SiCl2 Hydrated zeolites are used as ion exchangers in softening of “hard”
water.

SCAN CODE
p-Block (Group 13 and 14)
p-BLOCK (GROUP 13 AND 14) 53

Summary
Group 13 Group 14
Physical Property Remarks Physical Property Remarks
Atomic Radii  B < Al > Ga < In < Tl Atomic Radii  C < Si < Ge < Sn < Pb
Ionisation Energy  B > Tl > Ga > Al > In Ionisation Energy  C > Si > Ge > Sn < Pb
Electronegativity  B > Tl > In > Ga > Al Electronegativity  C > Si = Ge = Sn < Pb
Oxidation state  General oxidation states: +1, +3 Oxidation state  General oxidation states: +2, +4
Metallic character  Increases down the group Metallic character  Increases down the group
Melting point  Decreases up to Ga then increases Melting point  Decreases up to Sn then increases
Boiling point  Decreases down the group Boiling point  Decreases down the group
Density  Increases down the group Density  Increases down the group

Chemical Property Remarks Chemical Property Remarks

Reactivity with  Reacts with air to form oxide (at mod Reactivity with air  Reacts with air to form monoxide and
air erate temp.) and nitride (at high temp.) dioxides
Crystalline boron unreactive, amor Reactivity with  Only Sn reacts with steam. Rest all do
phous boron reacts. Aluminium forms water not react with water in any form
oxide layer and does not react further.
Reactivity with  Reacts with halogens to form
Reactivity with  Boron does not react. halogens halogens dihalides and tetrahalides
acids and alkalis Aluminium reacts with both acids and
alkalis to liberate hydrogen gas.
Aluminium passive with conc.
nitric acid.
Reactivity with  Reacts with halogens to form
halogens trihalides (except tri-iodide of
Thallium)
Nature of  Boron - acidic, Al and
trioxides Ga - amphoteric, In and Tl - Basic

SCAN CODE
p-Block (Group 13 and 14)
54 p-BLOCK (GROUP 13 AND 14)

Solved Examples
Example-1 state is more stable than the Tl. In Tl, the +1 state is more
Discuss the pattern of variation in the oxidation states of stable.
(i) B to Tl and Example-3
(ii) C to Pb. Why does boron trifluoride behave as a Lewis acid?
Sol. (i) B to Tl: This elements are belongs to group 13. The Sol. Boron trifluoride behave as a Lewis acid. Boron trifluroides
electronic configuration of this group are ns2 np1. Most are electron deficient species. boron halides have three
common oxidation state should be +3 but it is only boron covalent bonds hence, require two electrons to complete
and aluminium. Ga, In, Tl, show both the +1 and +3 oxidation octet.
states. On moving down the group, the +1 state becomes
more stable due to transition contraction. But for Tl (+1) is
more stable than Tl (+3) because of the inert pair effect. The
stability of the +3 oxidation state decreases on moving
down the group.
Group 13 element Oxidation state
B +3
Al +3
Ga, In, Tl +1, +3
Example-4
(ii) C to Pb
These elements are belonging to group 14. The electronic Consider the compounds, BCl3 and CCl4. How will they
configuration of this group are ns2 np 2. Most common behave with water? Justify.
oxidation state should be +4. The elements of group 14
Sol. BCl3 is electron deficient species. When it reacts with
show tetra valency by sharing four of its valence electrons.
But Ge, Sn, Pb also show +2 oxidation state due to inert pair electron rich species like water, it reacts fastly and formed
effect. the stability of the lower oxidation state increases boric acid.
and that of the higher oxidation state decreases on moving
down the group.
BCl3  3H 2 O  3HCl  B  OH 3
Group 14 element Oxidation state In case of CCl4, it cannot increase the coordination number
C +4 due to unavailability of vacant d orbital.
Si +4 Example-5
Ge, Sn, Pb +2, +4
Is boric acid a protic acid? Explain.
Example-2
Sol. Boric acid only partially reacts with water to form H3O+ and
How can you explain higher stability of BCl3 as compared
to TlCl3? [B(OH)4]-, it behaves as a weak acid.

Sol. Elements of 13 group reacts with halogens to form trihalides. B  OH 3  2HOH   B  OH  4   H 3 O 
BCl3 is more stable than TlCl3 because the boron +3 oxidation
It does not donate protons like other acids.
p-BLOCK (GROUP 13 AND 14) 55
Example-6 Example-9
Explain what happens when boric acid is heated. What are electron deficient compounds? Are BCl3 and SiCl4

 
electron deficient species?
H3 BO3  HBO2  B2 O3
370 K red hot
Sol. Explain.
Metaboric acid Boric oxide
Sol. Electron deficient species are those species in which the
Example-7 octet of the central metal atom is not complete.
Describe the shapes of BF 3 and BH 4 . Assign the –
(i) BCl3
hybridisation of boron in these species.
Boron trichloride behave as a Lewis acid. It is electron
Sol. deficient species. boron tri-chloride have three covalent
(i) BF3 : Broon trifluoride are planar molecule in which central bonds hence, require two electrons to complete octet.
atom is sp2 hybridized. An sp2 hybridized boron atom has (ii) SiCl4
an empty p-orbital which can accept a pair of electron. BF3 Silicon is belonging to group 14. The electronic
is shorter and stronger due to p  -p  back bonding. configuration of this group are ns2 np2. Most common
oxidation state should be +4. The elements of group 14
show tetra valency by sharing four of its valence electrons.
it forms four covalent bonds with four chlorine atoms.
Therefore, SiCl4 is not an electron-deficient compound.
Example-10
Write the resonance structures of CO 32  and HCO 3 .
Sol. (a) CO 32–

(ii) BH 4 : Boron-hydride ion hybridization is sp 3. it is

BH
tetrahedral in structure.

Example-8
Write reactions to justify amphoteric nature of aluminium. There are three resonating structures for the carbonate
ion.
Sol. Amphoteric: When the substance reacts with acid as well (b) HCO 3–
as base then substance known as amphoteric in nature.
Aluminum is amphoteric because it reacts with acid as well
as base.

(i) 2Al(s)  6HCl(aq)  2Al3 (aq)  6Cl  (aq)  3H 2(g)

There are only two resonating structures for the bicarbonate
(ii) ion.

2Al(s) 2NaOH (aq) 6H 2 O(l) 2Na   Al  OH 4   3H 2(g )
(aq)
56 p-BLOCK (GROUP 13 AND 14)

Example-11 Hence, PbCl4 is much less stable than PbCl2. However, the
What is the state of hybridisation of carbon in formation of PbCl4 takes place when chlorine gas is bubbled
through a saturated solution of PbCl2.
(a) CO 32 
PbCl2(s)  Cl 2(g)  PbCl4(l)
(b) Diamond
(c) Graphite? (b) The stability of the lower oxidation state increases and that
of the higher oxidation state decreases on moving down
Sol. The state of hybridisation of carbon in the given substance
the group. Pb(IV) is highly unstable and when heated, it
are:
reduces to Pb(II).
Substance Hybridization of carbon

PbCl4(l)   PbCl 2(s)  Cl 2(g)
CO32– sp 2
Diamond sp 3 (c) Lead is known not to form PbI4 due to I- is strong reducing
Graphite sp 2 agent which reduces
Example-12 Pb+4 to Pb+2 and also stability of +4 oxidation state of lead is
Explain the difference in properties of diamond and graphite lesser than +2 state.
on the basis of their structures. Example-14
Sol. Suggest reasons why the B–F bond lengths in BF3 (130
Diamond Graphite pm) and BF4 (143 pm) differ..
It is hardest substance. It is soft substance.
Hybridisation of each Hybridization of each Sol. Boron trifluoride are planar molecule in which central atom
carbon is sp3 carbon atom is sp2 is sp2 hybridized. An sp2 hybridized boron atom has an
Geometry is tetrahedral Geometry is planar empty p-orbital which can accept a pair of electron. BF3 is
Bad conductor of electricity Good conductor of electricity shorter and stronger due to p  -p  back bonding. This
due to free electron. imparts a double bond character to the B–F bond.
Not layered structure Layered structure
Used for making cutters Used as lubricant
Example-13
Rationalise the given statements and give chemical
reactions:
• Lead (II) chloride reacts with Cl2 to give PbCl4.
• Lead (IV) chloride is highly unstable towards heat.
• Lead is known not to form an iodide, PbI4. Bond length to shorten in BF3 (130 pm) due to double-bond
Sol. character.

(a) Lead belongs to group 14. The electronic configuration But in case of BF4- a change in hybridisation from sp2 to
of this group are ns2 np2. Most common oxidation state sp3. There is no double bond character because vacant
should be +4. The elements of group 14 show tetra valency orbital filled by other fluoride ion and B–F bond length of
by sharing four of its valence electrons. But Pb show +2 143 pm in BF4 ion.
oxidation state due to inert pair effect. the stability of the
lower oxidation state increases and that of the higher
oxidation state decreases on moving down the group.
p-BLOCK (GROUP 13 AND 14) 57

Example-17
B (OH)3 + NaOH  NaBO2 + Na [B (OH)4] + H2O
How can this reaction is made to proceed in forward
direction?
(a) Addition of cis 1, 2 diol
(b) Addition of borax
Example-15
(c) Addition of trans 1, 2 diol
If B–Cl bond has a dipole moment, explain why BCl3 (d) Addition of Na2HPO4
molecule has zero dipole moment. Ans. (a)
Sol. Boron trichloride are planar molecule in which central atom Sol. B  OH 3  NaOH  NaBO 2  Na  B  OH 4   H 2 O
is sp2 hybridized. It is a symmetrical molecule. Hereafter,
in this reaction, if you added cis 1,2-diol, then the product
the dipole-moments of the B–Cl bond cancel each other,
Na  B  OH 4  reacts with cis 1,2 -diol and produces a
thereby causing results zero-dipole moment
cyclic product and free water molecules. Due to the
formation of cyclic products and four water molecules the
entropy of the reaction increases, so the reaction becomes
more feasible. Therefore, this reaction is made to proceed
in the forward direction by the addition of cis 1, 2 diols. The
reaction is shown below,
OH O OH
HC HC
+ B(OH)—4 B + 2H2O
Example-16 HC OH HC O OH

 Na  B(OH) 4 
B(OH)3  NaOH 
1 : 1 polyol-boron complex

How can this reaction be made to proceed in forward direc- OH O O CH

HC HC
tion? 2 + B(OH)—4 B + 4H2O
(a) Addition of cis-1,2-diol HC OH HC O O CH

(b) Addition of borax bis-1, 2-diol 2 : 1 polyol-boron complex

(c) Addition of trans-1, 2-diol Example-18
(d) Addition of Na2HPO4 Which of the following minerals does not contain aluminium?
Ans. (a) (a) Cryolite (b) Mica
Sol. Boric acid on reaction with NaOH gives sodium (c) Feldspar (d) Fluorspar
metaborate as product. Because of aqueous conditions, Ans. (d)
this reaction is reversible in nature. Sodium metaborate gets Sol. Cryolite, mica, feldspar are ores of aluminium with
hydrolysed back to give boric acid and NaOH. In order to chemical formula given below:
prevent the reversibility of reaction add some polyhydroxy
compound such as glycerol, mannitol or 1, 2 cis- diols. Mica  KAl2  AlSi3 O10   OH 2
These polyhydroxy compounds can form chelate complex Cryolite  Na 3 AlF6
with sodium metaborate and prevent it to get hydrolysed.
Fluorspar  CaF2

Feldspars are the aluminosilicates with general formula

AT4 O8 .
58 p-BLOCK (GROUP 13 AND 14)

Example-19 Example-23
Aluminium chloride exists as dimer, Al2Cl6 in solid state as H 2O Heat NaOH
SiCl 4   X  Y  Z
well as in solution of non-polar solvents such as benzene.
When dissolved in water, it gives X, Y and Z in the above reaction are
(a) [Al(OH)6]3– + 3HCl (b) [Al(H2O)6]3+ + 3Cl– X Y Z
(c) Al3+ + 3Cl– (d) Al2O3 + 6HCl (a) SiO2 Si NaSi
Ans. (b) (b) Si(OH)4 SiO2 Na2SiO3
Sol. Aluminium chloride can form a dimer like Al 2 Cl 6 . In (c) Si(OH)4 Si SiO2
(d) SiO2 SiCl4 Na2SiO3
solid-state as well as in the solution of non-polar solvents
such as benzene aluminum chloride exists as a dimer. When Ans. (b)
it dissolves in water, it gives aluminium hexa hydroxide Sol. Silicon tetrachloride on reaction with water gives o-silicilic
anion with hydrochloric acid, as follows. acid and HCl. This acid on heating gives silica which is
acidic in nature. Therefore, silica on reaction with base like
Al2 Cl6  12H 2 O  2[ Al( H 2 O) 6 ]3  6Cl 
NaOH gives sodium salt of silicate and water as shown in
Example-20 the reactions:
Which of the following hydrides is least stable to hydrolysis? SiCl 4  4H 2 O  Si  OH 4 (X)  4HCl
(a) CH4 (b) SiH4
Si  OH 4 

 SiO 2 (Y)  H 2 O
(c) SnH4 (d) PbH4
SiO 2  2NaOH  Na 2SiO 3 (Z)  H 2 O
Ans. (d)
Example-24
Sol. PbH 4 is the least stable due to inert pair effect. An oxide X in its normal form is almost non-reactive due to
Example-21 very high X – O bond enthalpy. It resists the attack by
Which of the following is not a use of graphite ? halogens, hydrogen and most of acids and metals even at
(a) For electrodes in batteries. elevated temperatures. It is only attacked by HF and NaOH.
The oxide X is
(b)Crucibles made from graphite are used for its
inertness to dilute acids and alkalies. (a) SiO2 (b) CO2
(c) For adsorbing poisonous gases. (c) SnO2 (d) PbO2
(d) Lubricant at high temperature. Ans. (a)
Ans. (c) Sol. SiO2 have giant covalent structure and is not attacked by
Sol. Graphite is not used for absorbing poisonous gas. halogen, metal at high temp. But react with HF and
Example-22 NaOH.
Which property of CO 2 makes it of biological and Example-25
geochemical importance ? Silicon has a strong tendency to form polymers like silicones.
(a) Its acidic nature. The chain length of silicone polymer can be controlled by
(b) Its colourless and odourless nature. adding
(c) Its low solubility in water. (a) MeSiCl3 (b) Me2SiCl2
(d) Its high compressibility. (c) Me3SiCl (d) Me4Si
Ans. (c) Ans. (c)
Sol. Chain length of silicones polymer can be controlled by add-
Sol. CO 2 have low solubility in water..
ing Me3SiCl act as inhibitor of reaction.
p-BLOCK (GROUP 13 AND 14) 59

EXERCISE - 1 : Basic Objective Questions

Introduction to p-block Elements Physical and Chemical Properties of Group 13
1. The shapes and hybridisation of BF 3 and BH 4 Elements
respectively are 5. Ionisation enthalpy ( i H1 kJ mol1 ) for the elements
(a) BF3 - Trigonal, sp2 hybridisation ; of Group 13 follows the order
BH 4 - Square planar, sp3 hybridisation (a) B > Al > Ga > In > Tl (b) B < Al < Ga < In < Tl
(c) B < Al > Ga > In > Tl (d) B > Al < Ga > In < Tl
(b) BF3 - Triangular, sp3 hybridisation ;
6. The stability of +1 oxidation state increases in the se-
BH 4 - Hexagonal, sp3d hybridisation quence:
(c) BF3 - Trigonal, sp2 hybridisation ; (a) Tl < In < Ga < Al (b) In < Tl < Ga < Al
(c) Ga < In < Al < Tl (d) Al < Ga < In < Tl
BH 4 - Tetrahedral, sp3 hybridisation 7. Group 13 elements show +1 and +3 oxidation states.
3
(d) BF3 - Tetrahedral, sp hybridisation ; Relative stability of +3 oxidation state may be given as

BH 4 - Tetrahedral, sp3 hybridisation. (a) Tl3  In3  Ga 3  Al3  B3

2. Which of the following is a Lewis acid ? (b) B3  Al3  Ga 3  In 3  Tl3
(a) AlCl3 (b) MgCl2
(c) CaCl2 (d) BaCl2 (c) Al3  Ga 3  Tl3  In 3  B3
3. Specify the coordination geometry around and hybrid-
(d) Al3  B3  Ga 3  Tl3  In 3
ization of N and B atoms in 1:1 complex of BF3 and NH3:
(a) N: tetrahedral, sp3 ; B:tetrahedral, sp3 8. Aluminium exhibits +3 oxidation state. As we move down
(b) N: pyramidal, sp ; B:pyramidal , sp
3 3 the group, +1 oxidation state gets more stable. This is a
consequence of
(c) N:pyramidal, sp3 ; B:planar, sp3
(a) increasing size of the atom
(d) N:pyramidal, sp3 ; B:tetrahedral, sp3
(b) inert pair effect
4. Trimethylammonia is pyramidal whereas trisilylammonia
is a planar molecule. Why ? (c) electron deficient nature
(d) p - p bonding.
9. Which one of the statements is incorrect for aluminium
metals?
(a) It is a good conductor of heat and electricity
(b) It is malleable and ductile
(c) It can be welded and cast but difficult to solder
(a) In silicon atom, the electron pair of nitrogen is involved (d) Its alloys are heavy
in p - d bonding. 10. The reason behind the lower atomic radius of Ga as
(b) In nitrogen, lone pair of electrons is present at compared to Al is
nitrogen hence it has pyramidal shape. (a) poor screening effect of d-electrons for the outer
(c) Both (a) and (b) are correct. electrons from increased nuclear charge
(d) Both (a) and (b) are wrong. (b) increased force of attraction of increased nuclear
charge on electrons
(c) increased ionisation enthalpy of Ga as compared to
Al
(d) anomalous behaviour of Ga.
60 p-BLOCK (GROUP 13 AND 14)
11. Electropositive charcter for the elements of group 13 (d) p—p back bonding
follows the order 21. When aluminium hydroxide dissolves in NaOH solution,
(a) B > Al > Ga > In > Tl (b) B < Al < Ga < In < Tl the product is:
(c) B < Al > Ga < In > Tl (d) B < Al > Ga > In > Tl (a) [Al(H2O)3(OH)3]
12. Aluminium is more reactive than iron. But aluminium is (b) [Al(H2O)4(OH)2]+
less easily corroded than iron because: (c) [Al(H2O)2(OH)4]–
(a) oxygen forms a protective oxide layer on aluminium (d) [Al(H2O)5(OH)]2+
(b) aluminium is a noble metal 22. Which of the following does not show similarity
(c) iron undergoes reaction easily with water between boron and aluminium ?
(d) iron forms mono and divalent ions (a) Both form oxides of type M2O3 when heated with
13. Aluminium does not react with:
oxygen at high temperature.
(a) NaOH (b) HCl
(b) Both dissolve in alkalies and evolve hydrogen.
(c) N2 (d) HNO3
(c) Hydroxides of both the elements are basic in nature.
14. When aluminium is heated with conc. H2SO4
(d) Both form nitrides of MN type when heated with N2.
(a) aluminium becomes passive
23. The exhibition of highest co-ordination number depends
(b) hydrogen is liberated on the availability of vacant orbitals in the central atom.
(c) oxygen is liberated Which of the following elements is not likely to act as
(d) sulphur dioxide is liberated
central atom in MF63 ?
15. Which of the following hydroxides is acidic ?
(a) B (b) Al
(a) Al(OH)3 (b) Ga (OH)3
(c) Ga (d) In
(c) Tl (OH)3 (d) B(OH)3
24. Which one of the following statements regarding BF3 is
16. Which of the following oxides is acidic in nature ? not correct?
(a) B2O3 (b) Al2O3 (a) It is a Lewis acid
(c) Ga2O3 (d) In2O3 (b) It is an ionic compound
17. The element which exists in liquid state for a wide range (c) It is an electron deficient compound
of temperature and can be used for measuring high (d) It forms adducts
temperature is 25. BF3 is used as catalyst in several industrial processes
(a) B (b) Al due to its:
(c) Ga (d) In (a) strong reducing nature
18. Boron is unable to form BF63 ions due to (b) weak reducing action
(c) strong Lewis acid nature
(a) non-availability of d-orbitals
(d) weak Lewis acid character
(b) small size of boron atom
26. The decreasing order of power of boron halides to act as
(c) non-metallic nature Lewis acids is
(d) it is a strong Lewis acid.
(a) BF3  BCl3  BBr3
19. Which of the following compounds are formed when
boron trichloride is treated with water? (b) BBr3  BCl3  BF3
(a) H3BO3 + HCl (b) B2H6 + HCl
(c) BCl3  BF3  BBr3
(c) B2O3 + HCl (d) None of these
20. The main factor responsible for weak acidic nature of (d) BCl3  BBr3  BF3
B—F bonds in BF3 is:
(a) high electronegativity of F
(b) three centred two electron bonds in BF3
(c) p—d back bonding
p-BLOCK (GROUP 13 AND 14) 61
27. In BX3, B – X distance is shorter than what is expected (d) in making optical glasses.
theoretically because (X = F, Cl, Br, I) 33. Which is the hardest compound of boron ?
(a) B2O3 (b) BN
(c) B4C (d) B2H6
34. Which of the following is the electron deficient molecule ?
3
(a) sp hybridisation of B is responsible for shorter (a) B2H6 (b) C2H6
B – X distance. (c) PH3 (d) SiH4
(b) B – X has a double bond character due to back- 35. Which of the following compounds are formed when
bonding. BCl3 is treated with water ?
(c) Dimerisation takes place in BX3 which is responsible (a) H3BO3 (b) B2H6
for shorter B – X distance.
(c) B2O3 (d) HBO2
(d) Due to large size of X, B – X distance decreases.
36. The geometry of a complex species can be understood
28. Identify X and Y in the following reaction.
from the knowledge of type of hybridisation of orbitals
140ºC NaBH of central atom. The hybridisation of orbitals of central
BCl3  NH 4 Cl 
C H Cl X 
4
Y
6 5 atom in [B(OH)4]– and the geometry of the complex are
(a) X = NaBO2, Y = B2O3 respectively
(b) X = Na2B4O7, Y = H3BO3 (a) sp3, tetrahedral (b) sp3, square planar
3 2
(c) sp d , octahedral (d) dsp2, square planar.
(c) X = BN, Y = [NH 4 ] [BCl4 ]
37. On the addition of mineral acid to an aqueous solution
(d) X = B3N3H3Cl3, Y = B3N3H6 of borax, the following compound is formed:
29. A gas other than HCl is obtained in : (a) boron hydride (b) orthoboric acid
Silent electric
(a) BCl3 + H 2  (c) metaboric acid (d) pyroboric acid
discharge 
 
(b) LiAlH 4 + BF3  38. Na 2 B4 O7 .10H 2 O   X  YZ

(c) Both (d) None of these X, Y and Z in the reaction are

30. Which of the following statements about anhydrous alu- (a) X  Na 2 B 4 O 7 , Y  NaBO 2 , Z  B 2 O 3
minium chloride is correct?
(b) X  Na 2 B4 O7 , Y  B2 O3 , Z  H 3 BO3
(a) It exists as AlCl3 molecule
(b) It is a strong Lewis base (c) X  B2 O3 , Y  NaBO 2 , Z  B(OH)3
(c) It sublimes at 100 C under vaccum
o

(d) X  NaBO 2 , Y  B2 O3 , Z  B(OH)3

(d) It is not easily hydrolysed
39. Borax is used as a cleansing agent because on dissolv-
ing in water, it gives:
Boron and Its Compounds
(a) alkaline solution (b) acidic solution
(c) bleaching solution (d) neutral solution
31. Which is not the use of orthoboric acid ?
40. The number of OH units directly linked to boron atoms
(a) As an antiseptic and eye wash. in Na2B4O7.10H2O is:
(b) In glass industry. (a) 2 (b) 3
(c) In glazes for pottery. (c) 4 (d) 10
(d) In borax - bead test. 41. Borax bead test is responded by:
32. Borax is not used (a) divalent metals (b) heavy metals
(a) as a styptic to stop bleeding (c) light metals
(b) in making enamel and pottery glazes (d) metals which form coloured metaborates
(c) as a flux in soldering
62 p-BLOCK (GROUP 13 AND 14)
42. What happens when a mixture of cobalt oxide and borax 49. Orthoboric acid behaves as a weak monobasic acid
is heated in a flame on a loop of platinum wire ? giving H3O+ and
(a) A transparent white bead is formed. (a) [B(OH)4]+ (b) H2BO2+
(b) A bright pink coloured NaBO2 bead is formed. (c) [B(OH)4]– (d) H2BO2–
(c) A blue coloured Co(BO2)2 bead is formed. 50. On hydroloysis, diborane produces
(d) A red coloured Co(BO2)2 bead is formed. (a) H3BO2 + H2O2 (b) H3BO3 + H2
43. Which of the following compounds is formed in borax (c) B2O3 + O2 (d) H3BO3 + H2O2
bead test? 51. In diborane,
(a) Metaborate (b) tetraborate (a) four bridged hydrogen atoms and two terminal
(c) Double oxide (d) Orthoborate hydrogen atoms are present
44. Boric acid H3BO3 and BF3 have the same number of elec- (b) two bridged hydrogen atoms and four terminal
trons. The former is a solid and the latter is a gas. The hydrogen atoms are present
reason is: (c) three bridged hydrogen atoms and three terminal
(a) BF3 is a Lewis acid while B(OH)3 is not hydrogen atoms are present
(b) they have different geometrics (d) there are no bridged hydrogen atoms in diborane,
(c) In BF3, F– is smaller in size than OH– in B(OH)3 only hydrogen bonds are present.
(d) No molecular association is possible in BF3 while it 52. The type of hybridization of boron in diborane is
is possible in B(OH)3 due to hydrogen bonding (a) sp-hybridization (b) sp2-hybridization
45. H3BO3 is: (c) sp3-hybridization (d) sp3d2-hybridization.
(a) monobasic and weak Lewis acid 53. In diborane, the two H – B – H angles are nearly :
(b) monobasic and weak Bronsted acid (a) 60º, 120º (b) 95º, 120º
(c) monobasic acid and strong Lewis acid (c) 95º, 150º (d) 120º, 180º
(d) tribasic acid and weak Bronsted acid
54. The structure of diborane (B2H6) contains :
46. An aqueous solution of boric acid is found to be weakly
(a) four 2C-2e bonds and two 3C-2e bonds
acidic in nature. This acidic character arises due to the
(b) two 2C-2e bonds and four 3C-2e bonds
following reasons.
(c) two 2C-2e bonds and two 3C-3e bonds
(a) It is a protic acid which donates protons in aqueous
solution. (d) four 2C-2e bonds and four 3C-2e bonds
55. In B2H6:
(b) It is a Lewis acid which abstracts OH– from water
(a) there is direct boron-boron bond
and leaves H+ to make the solution acidic.
(b) the boron atoms are linked through hydrogen bridges
(c) It gives metaboric acid when dissolved in water.
(c) the structure is similar to C2H6
(d) It is prepared by reaction of borax with sulphuric
(d) all the atoms are in one plane
acid hence it behaves as an acid.
56. Borazole, B3N3H6 is related to benzene as:
47. Boric acid is prepared from borax by the action of :
(a) isoelectronic (b) isostructural
(a) Hydrochloric acid (b) sodium hydroxide
(c) both (a) and (b) (d) none of these
(c) carbon dioxide (d) sodium carbonate
57. Which of the following compounds is known as inor-
48. Boric acid has a polymeric layer structure in which
ganic benzene?
planar BO3 units are joined by
(a) B6H6 (b) C5H5B
(a) covalent bonds
(c) C3N3H3 (d) B3N3H6
(b) two centre - two electron bonds
58. The bonds present in borazole are:
(c) coordinate bonds
(a) 9, 9 (b) 6, 6
(d) hydrogen bonds.
(c) 9, 6 (d) 12, 3
p-BLOCK (GROUP 13 AND 14) 63
59. Boron nitride can be represented by the given structure. 65. The main factor responsible for weak acidic nature of
B—F bonds in BF3 is:
(a) high electronegativity of F
(b) three centred two electron bonds in BF3
(c) p—d back bonding
(d) p—p back bonding
66. The power of halides of boron to act as Lewis acids
decreases in the order:
(a) BF3 > BCl3 > BBr3 (b) BBr3 > BCl3 > BF3
(c) BCl3 > BF3 > BBr3 (d) BCl3 > BBr3 > BF3
The structure of BN is similar to 67. Which of the following is a false statement ?
(a) graphite (b) diamond (a) BH3 is not a stable compound
(c) benzene (d) pyridine. (b) Boron hydrides are formed when dil. HCl reacts with
60. NaBH4 + I2  X + Y + Z Mg3B2
(c) All the B—H bond distances in B2H6 are equal
450 K
BF3 + NaH  X+P
(d) The boron hydrides are readily hydrolysed
BF3 + LiAlH4  X + Q + R 68. Which of the following is not true regarding the nature
X, Y, Z, P, Q and R in the reactions are of halides of boron ?
X Y Z P Q R (a) Boron trihalides are covalent.
(a) Na4B4O7 NaI HI HF LiF AlF3 (b) Boron trihalides are planar triangular with sp2
(b) B2H6 NaI H2 NaF LiF AlF3 hybridisation
(c) B2H6 BH3 NaI B3N3H6 Al2F6 AlF3 (c) Boron trihalides act as Lewis acids.
(d) BH3 B2H6 H2 B3N3H6 LiF AlF3 (d) Boron trihalides cannot be hydrolysed easily.
61. Boron cannot form which one of the following anions? 69. Na2B4O7.10H2O is correctly represented as:
(a) 2NaBO2.Na2B2O3.10H2O
(a) BF6 (b) BH 4
(b) Na2[B4O5(OH)4].8H2O
(c) [B(OH)4]– (d) BO 2 (c) Na2[B4(H2O)4O7].6H2O
62. The hardest compound of boron is: (d) all of these
(a) boric acid (b) boron nitride 70. In the structure of diborane
(c) boron carbide (d) boron hydride (a) all hydrogen atoms lie in one plane and boron atoms
63. Which one of the following is the correct statement ? lie in a plane perpendicular to this plane
(b) 2 boron atoms and 4 terminal hydrogen atoms lie in
(a) B 2H6  2NH3 is known as ‘inorganic benzene’.
the same plane and 2 bridging hydrogen atoms lie in
(b) Boric acid is a protonic acid. the perpendicular plane
(c) Beryllium exhibits coordination number of six. (c) 4 bridging hydrogen atoms and boron atoms lie in
(d) Chlorides of both beryllium and aluminium have one plane and two terminal hydrogen atoms lie in a
bridged chloride structures in solid phase. plane perpendicular to this plane
64. BCl3 does not exist as a dimer but BH3 exists as B2H6 (d) all the atoms are in the same plane.
because
71. Boric acid is used in carrom boards for smooth gliding of
(a) Cl2 is more electronegative than hydrogen pawns because:
(b) large size of chlorine atom does not fit between small (a) H3BO3 molecules are loosely chemically bonded and
sized boron atoms, while small-sized hydrogen hence it is soft
atoms occupy the space between boron atoms
(b) its low density makes it fluffy
(c) there is p-dback bonding in BCl3
(c) it is chemically inert with the plywood
(d) both (b) and (c)
(d) H-bonding in H3BO3 gives it a layered structure
64 p-BLOCK (GROUP 13 AND 14)
80. Reactivity of borazole is higher than that of benzene
Z  X 
B  LiH  Y  LiBH
72. 4 because:
Heat
(a) borazole is a polar compound
Which of the statement is true for the above sequence (b) borazole is a non-polar compound
of reactions? (c) borazole is electron deficient compound
(a) Z is hydrogen (b) X is B2H6 (d) of localised electrons in it
(c) Z and Y are F2 and B2H6 respectively [Note: In benzene, -electrons are delocalised over the
(d) Z is potassium hydroxide ring which give stability to benzene ring.]
81. Which of the following is correct?
73. Na 2 B4 O 7  X  H 3 BO3 . What is X in the reaction ?
(a) The members of BnHn+6 are less stable than BnHn+4
(a) Aqueous solution of NaOH series
(b) Dilute nitric acid (b) Diborane is coloured and unstable at room tempera
(c) Conc. H2SO4 or HCl ture
(d) Water (c) The reaction of diborane with oxygen is endothermic
74. When strongly heated, orthoboric acid leaves a residue (d) All of the above
of:
(a) metaboric acid (b) tetraboric acid
Aluminium and Its Compounds
(c) boric anhydride (d) boron
o o
75. H 3 BO3 
100 C
 X 
160 C
 Y 
Re d hot
B2 O3 ; 82. Thermite is a mixture of iron oxide and
X and Y respectively are: (a) aluminium powder (b) zinc powder
(a) X = Metaboric acid ; Y = Tetraboric acid (c) iron turnings (d) copper turnings.
(b) X = Borax; Y = Metaboric acid 83. Alumina is:
(c) X = Tetraboric acid ; Y = Metaboric acid (a) acidic (b) basic
(d) X = Tetraboric acid ; Y = Borax (c) neutral (d) amphoteric
76. From B2H6, all the following can be prepared except: 84. Which one is the wrong statement ?
(a) B2O3 (b) H3BO3 (a) Aluminium is the most abundant metal in the earth’s
crust
(c) B2(CH3)6 (d) NaBH4
(b) Aluminium is not affected by strong alkalies
77. A mixture of boron trichloride and hydrogen is subjected
(c) Aluminium becomes passive with conc. HNO3
to silent electric discharge to form ‘A’ and HCl. ‘A’ is
(d) Aluminium when heated in the atmosphere of
mixed with NH3 and heated to 200oC to form ‘B’. The
nitrogen forms a nitride of the formula AIN.
formula of ‘B’ is:
[Hint: Al is affected by strong alkalies with evolution of
(a) H3BO3 (b) B2O3
hydrogen. ]
(c) B2H6 (d) B3N3H6
85. Aluminium vessels should not be washed with materials
78. Diborane reacts with ammonia under different conditions
containing washing soda since :
to give a variety of products. Which one among the
(a) washing soda reacts with aluminium to form soluble
following is not fomed in these conditions?
aluminate
(a) B2H6.2NH3 (b) B12H12
(b) washing soda is expensive
(c) B3N3H6 (d) (BN)n
(c) washing soda is easily decomposed
79. What are X and Y in the reaction ?
(d) washing soda reacts with aluminium to form insoluble
3B2 H6  6X  3 [BH 2 (X) 2 ] [BH4 ] 
heat
 Y  12H 2 aluminium oxide

(a) X = NH3, Y = B3N3H6 (b) X = CO, Y = BH3CO

(c) X = NaH, Y = NaF (d) X = NF3, Y = B3N3
p-BLOCK (GROUP 13 AND 14) 65
(c) heating it with rock salt
86. Al2O3 formation from aluminium and oxygen involves
evolution of a large quantity of heat, which makes alu- (d) mixing it with carbon and heating the mixture in a
minium used in: current of dry chlorine
(a) deoxidiser (b) confectionary 94. Heating an aqueous solution of aluminium chloride to
(c) indoor photography (d) thermite welding dryness will give
87. When a solution of sodium hydroxide is added in excess (a) AlCl3 (b) Al2Cl6
to the solution of potash alum, we obtain: (c) Al2O3 (d) Al(OH)Cl2
(a) a white precipitate (b) bluish white precipitate 95. Which of the following will be formed, if we heat an
(c) a clear solution (d) a crystalline mass aqueous solution of AlCl3 to dryness ?
88. When excess of NaOH solution is added in potash alum, (a) Solid AlCl3 (b) Dimer Al2Cl6
the product is: (c) Al(OH)3 (d) Al2O3
(a) a bluish white precipitate 96. When alumina is heated with carbon in nitrogen atmo-
(b) clear solution sphere, the products are:
(c) a white precipitate (d) a greenish precipitate (a) Al + CO (b) Al + CO2
[Hint: Alum consists Al2 (SO4)3 reacts with NaOH. (c) Al + CO + CO2 (d) AlN + CO
The other sulphates K2SO4 and Na2SO4 are also soluble 97. Alumina is:
in water. Thus, a clear solution is obtained.] (a) a bad conductor of electricity
89. AIF3 is soluble in HF only in presence of KF. It is due to (b) a good conductor of electricity
the formation of (c) a dehydrating agent
(a) K3[AlF6] (b) AlH3 (d) soluble in water
(c) K[AlF3H] (d) K3[AlF3H3] 98. Alumina is:
90. In the purification of bauxite by Hall’s process: (a) acidic (b) basic
(a) bauxite is heated with lime (c) neutral (d) amphoteric
(b) bauxite is heated with NaOH solution at 150 C o

(c) bauxite is heated with Na2CO3 solution

Physical and Chemical Properties of Group 14
Elements
(d) bauxite is heated at 1800oC in an atmosphere of N2
91. Select the true statements: 99. Maximum ability of catenation is shown by
(i) The formula of the corundum is Al2O3. (a) silicon (b) lead
(ii) The formula of cryolite is Na3AlF6. (c) germanium (d) carbon.
(iii) The formula of borax is Na2B4O7.10H2O 100. There is a large number of carbon compounds due to
(iv) The formula of bauxite is Al2O3.H2O (a) tetravalency of carbon
(a) (i), (ii) and (iii) (b) (ii), (iii) and (iv) (b) strong catenation property of carbon
(c) (i), (ii) and (iv) (d) (iii) and (iv) (c) allotropic property of carbon
92. Al2O3 can be converted to anhydrous AlCl3 by heating: (d) non-metallic character of carbon.
(a) a mixture of Al2O3 and carbon in dry Cl2 gas 101. Catenation i.e., linking of similar atoms depends on size
(b) Al2O3 with Cl2 gas and electronic configuration of atoms. The tendency of
(c) Al2O3 with HCl gas catenation in Group 14 elements follows the order
(d) Al2O3 with NaCl in solid state (a) C > Si > Ge > Sn (b) C > > Si > Ge  Sn
93. Alumina may be converted into anhydrous aluminium (c) Si > C > Sn > Ge (d) Ge > Sn > Si > C
chloride by: 102. Moderate electrical conductivity is shown by
(a) heating it with conc. HCl (a) silica (b) graphite
(b) heating in a current of dry chlorine (c) diamond (d) None of these
66 p-BLOCK (GROUP 13 AND 14)

103. Graphite is soft while diamond is hard because (a) (A)  (i), (B)  (ii), (C)  (iii), (D)  (iv)
(a) graphite is in powder form. (b) (A)  (iii), (B)  (i), (C)  (iv), (D)  (ii)
2
(b) diamond has sp -hybridisation but graphite has sp - 3 (c) (A)  (iv), (B)  (iii), (C)  (ii), (D)  (i)
hybridisation. (d) (A)  (i), (B)  (iii), (C)  (ii), (D)  (iv)
(c) graphite is in planar form while diamond is in 110. which of the following is not from 14 th group
tetrahedral form. (a) C (b) Pb
(d) graphite is covalent and diamond is ionic. (c) Si (d) /Na
104 The stability of dihalides of Si, Ge, Sn and Pb 111. Aluminium chloride exists as dimer, Al2Cl6 in solid state
increases steadily in the sequence as well as in solution of non-polar solvents such as
benzene. When dissolved in water, it gives
(a) PbX2 < SnX2 < GeX2 < SiX2
(a) [Al(OH)6]3– + 3HCl (b) [Al(H2O)6]3+ + 3Cl–
(b) GeX2 < SiX2 < SnX2 < PbX2
(c) Al3+ + 3Cl– (d) Al2O3 + 6HCl
(c) SiX2 < GeX2 < PbX2 < SnX2
112. An element of group 14 forms two oxides one of which is
(d) SiX2 < GeX2 < SnX2 < PbX2. highly poisonous and neutral. Other oxide can be easily
105. Which one of the following is not the characteristic liquefied and compressed to give a solid which is used
property of carbon ? as a refrigerant under the name of drikold. The element
(a) It exhibits catenation. and the oxides are
(b) It forms compounds with multiple bonds. (a) Si, SiO, SiO2 (b) Pb, PbO, PbO2
(c) Its melting point and boiling point are exceptionally (c) C, CO, CO2 (d) Sn, SnO, SnO2
high. 113. All members of group 14 when heated in oxygen form
(d) It shows semi-metallic character. oxides. Which of the following is the correct trend of
106. AlCl3 on hydrolysis gives: oxides ?
(a) Al2O3. H2O (b) Al(OH)3 (a) Dioxides CO2, SiO2 and GeO2 are acidic while SnO2
(c) Al2O3 (d) AlCl3.6H2O and PbO2 are amphoteric.
107. When excesss of carbon dioxide is passed through lime (b) CO, GeO, SnO and PbO are amphoteric.
water, the milkiness first formed disappears due to (c) Monoxides react with haemoglobin to form toxic
(a) the reversible reaction taking place compounds.
(b) formation of water soluble calcium bicarbonate (d) All oxides burn with blue flame.
(c) huge amount of heat evolved during the reaction 114. Identify the wrong example from the following for the
(b) formation of water soluble complex of calcium. group 14 elements.
108. Identify X in the reaction : (a) Element which forms most acidic dioxide-Carbon
(b) Element which is affected by water - Lead

X  2H 2 O   XO2  2H 2 (c) Commonly found in +2 oxidation state - Lead
(steam)
(d) Element used as semiconductor - Silicon
(a) C (b) Si
115. Which one of the following oxides is neutral ?
(c) Ge (d) Sn
(a) CO (b) SnO2
109. Match the column I with column II and mark the
appropriate choice. (c) ZnO (d) SiO2
Column I Column II 116. Which of the following oxides can act as a reducing
agent ?
(A) Coal gas (i) CO + H2
(a) CO (b) CO2
(B) Synthesis gas (ii) CH4
(c) SnO2 (d) PbO2
(C) Producer gas (iii) H2 + CH4 + CO
117. Sindoor is represented by
(D) Natural gas (iv) CO + N2
(a) Pb(NO3)2 (b) PbCO3Pb (OH)2
(c) Pb(OH)24PbCO3 (d) Pb3O4
p-BLOCK (GROUP 13 AND 14) 67
Carbon and Its Compounds 127. The members of group 14 form tetrahalides of the type
MX4. Which of the following halides cannot be readily
hydrolysed by water ?
118. The hardest substance is
(a) CX4 (b) SiX4
(a) iron (b) steel
(c) GeX4 (d) SnX4
(c) diamond (d) graphite
128. The most stable form of carbon at high temperature is X.
119. Buckminsterfullerence is
The C – C bond length in diamond is Y while C – C bond
(a) graphite (b) diamond
length in graphite is Z.
(c) C-60 (d) quartz.
What are X, Y and Z respectively ?
120. Which of the following does not depict properties of
(a) Graphite, 1.42 Å, 1.54 Å
fullerenes ?
(b) Coke, 1.54 Å, 1.84 Å
(a) Fullerenes are made by heating graphite.
(c) Diamond, 1.54 Å, 1.42 Å
(b) Fullerenes are pure forms of carbon.
(d) Fullerene, 1.54 Å, 1.54 Å
(c) Fullerenes have open cage structure like ice.
129. Identify the incorrect statement.
(d) C60 is called Buckminsterfullerene.
(a) Graphite is thermodynamically most stable allotrope
121. In graphite, C atom is in .......... state. of carbon.
(a) sp3 (b) sp (b) Other forms of elemental carbon like coke, carbon
(c) sp 2
(d) None of these black, charcoal are impure forms of graphite.
122. In graphite, the layers of carbon atoms are held by (c) All allotropes of carbon have thermodynamically
(a) covalent bonds different stability.
(b) coordinate bonds (d) Charcoal and coke are obtained by heating wood in
absence of air.
(c) van der Waals forces
130. Which of the following is not true about structure of
(d) ionic bonds.
diamond and graphite ?
123. What is the number of free electrons present on each
(a) In diamond, each carbon in sp3 hybridised while in
carbon atom in graphite ?
graphite each carbon is sp2 hybridised.
(a) Zero (b) 3
(b) In diamond, carbon atoms are closely packed in
(c) 2 (d) 1
crystal lattice while graphite has layer structure.
124. The purest form of coal is
(c) Diamond is a hard substance while graphite is a soft
(a) peat (b) anthracite substance.
(c) bituminous (d) lignite (d) Graphite is thermodynamically very less stable as
125. Carbon shows a maximum covalency of four whereas compared to diamond and is amorphous form of
other members can expand their covalence due to carbon.
(a) absence of d-orbitals in carbon 131. Which of the following is not a use of graphite ?
(b) ability of carbon to form p - p multiple bonds (a) For electrodes in batteries.
(c) small size of carbon (b) Crucibles made from graphite are used for its
(d) catenation of carbon. inertness to dilute acids and alkalies.
126.. Dry ice is (c) For adsorbing poisonous gases.
(a) solid NH3 (d) Lubricant at high temperature.
(b) solid SO2
(c) solid CO2
(d) solid N2.
68 p-BLOCK (GROUP 13 AND 14)

132. Match the column I with column II and mark the (c) increase in greenhouse effect, thus raising the
appropriate choice. temperature
Column I Column II (d) increase in formation of metal carbonates.
(A) Used as lubricant (i) Carbon dioxide 137. Which of the following acids cannot be stored in glass ?
(B) Oxide with three- dimensional (ii) Graphite (a) HF (b) HCl
structure (c) H2SO4 (d) HI
(C) Used in solar cells (iii) Silica 138. Silicon is an important constituent of
(D) Anhydride of carbonic acid (iv) Silicone (a) sand (b) atmosphere
(a) (A)  (iv), (B)  (iii), (C)  (ii), (D)  (i) (c) plants (d) water bodies
(b) (A)  (iv), (B)  (i), (C)  (iii), (D)  (ii) 139. Glass and cement are two important examples of
(c) (A)  (iii), (B)  (ii), (C)  (i), (D)  (iv) (a) man-made silicates (b) silicones
(d) (A)  (ii), (B)  (iii), (C)  (iv), (D)  (i) (c) zeolites (d) organic polymers.
133. Which is not a method of preparing carbon monoxide on 140. 4
In SiO , the tetrahedral molecule, two oxygen atoms
4
a commercial scale ?
are shared in
4731273 K
(a) C(s)  H 2 O (g) 
 CO (g)  H 2(g) (a) sheet silicates
(b) double-chain silicates
1273 K
(b) 2C (s)  O 2(g)  4N 2(g)  2CO (g)  4N 2(g) (c) chain silicates

(d) three-dimensional silicates.
(c) 2C(s)  O2(g)   2CO(g)
141. Which one of the following anions is present in the chain
373 K
structure silicates ?
(d) HCOOH 
conc. H2SO4  H 2 O  CO
(a) Si 2 O 76 (b) (Si 2 O 52 ) n
134 Carbon monoxide acts as a donor and reacts with certain
metals to give metal carbonyls. This is due to (c) (SiO32 ) n (d) SiO 44
(a) presence of one sigma and two pi bonds between C 142. Which of the following properties correctly explain SiO2 ?
and (a) Linear, basic
(b) presence of a lone pair on carbon atom in CO (b) Tetrahedral, acidic
molecule
(c) Tetrahedral, basic
(c) presence of lone pair on oxygen atom in CO molecule
(d) Linear, acidic
(d) poisonous nature of CO.
143. Which of the following is the correct statement about
135. Which of the following is not true about structure of silicones ?
carbon dioxide ?
(a) They are made up of SiO44 units.
(a) In CO2, carbon is sp - hybridised.
(b) C forms two sigma bonds one with each oxygen atom (b) They are polymers made up of R2SiO units.
and two p  p bonds. (c) They are water soluble compounds.
(c) CO2 is a linear covalent compound (d) They are hydrophillic in nature.
(d) It is a polar molecule. 144. A type of zeolite used to convert alcohols directly into
136. CO2 is not a poisonous gas but there is increase in gasoline is
concentration of CO2 in the atmosphere due to burning (a) zeolite A
of fossil fuels and decompostion of limestone. The (b) zeolite L
increase in concentration of CO2 may lead to (c) zeolite Beta
(a) increase in photosynthesis in plants (d) ZSM-5
(b) higher concentration of CO2 in water
p-BLOCK (GROUP 13 AND 14) 69

Inert Pair Effect 148. Which of the following halides is least stable and has
doubtful existence ?

145. Which of the following ions is the most stable ? (a) CCl4 (b) GeI4

(a) Sn2+ (b) Ge2+ (c) SnI4 (d) PbI4

149. The most commonly used reducing agent is
(c) Si2+ (d) Pb2+
(a) AlCl3 (b) PbCl2
146. The tendency of group 14 elements to show +2 oxidation
state increases in the order of (c) SnCl4 (d) SnCl2
(a) C < Si < Sn < Pb < Ge (b) C < Si < Ge < Sn < Pb 150. The stability of dihalides of Si, Ge, Sn and Pb
(c) Ge < Sn < Pb < C < Si (d) Pb < Sn < Ge < C < Si increases steadily in the sequence
147. In which of the following the inert pair effect is most (a) PbX2 < SnX2 < GeX2 < SiX2
prominent ? (b) GeX2 < SiX2 < SnX2 < PbX2
(a) C (b) Ge (c) SiX2 < GeX2 < PbX2 < SnX2
(c) Si (d) Pb (d) SiX2 < GeX2 < SnX2 < PbX2.
70 p-BLOCK (GROUP 13 AND 14)

EXERCISE - 2 : Previous Year Questions

1. Which of the following types of forces bind together 7. In graphite, electrons are (AIPMT 1997)
the carbon atoms in diamond? (AIPMT 1992) (a) localised on each C-atom
(a) Ionic (b) Covalent (b) localised on every third C-atom
(c) Dipolar (d) van der Waals (c) spread out between the structure
2. Which of the following statements about H3BO3 is (d) present in antibonding orbital.
not correct? (AIPMT 1994) 8. Which of the following does not show electrical
(a) It has a layer structure in which planar BO3 conduction? (AIPMT 1999)
units are joined by hydrogen bonds. (a) Diamond (b) Graphite
(b) It does not act as proton donor but acts as a (c) Potassium (d) Sodium
Lewis acid by accepting hydroxyl ion. 9. Percentage of lead in lead pencil is
(c) It is a strong tribasic acid. (AIPMT 1999)
(d) It is prepared by acidifying an aqueous solution (a) 80 (b) 20
of borax. (c) zero (d) 70
3. The type of hybridisation of boron in diborane is 10. Assertion: Silicones are hydrophobic in nature.
(AIPMT 1999) Reason: Si–O–Si linkages are moisture sensitive.
(a) sp -hybridisation
3 (AIIMS 2006)
(b) sp2-hybridisation (a) Both Assertion and Reason are true and Reason is the
(c) sp-hybridisation correct explanation of Assertion.
(d) sp3d2-hybridisation. (b) Both Assertion and Reason are true but Reason is not
4. Carbon and silicon belong to (IV) group. The the correct explanation of Assertion.
maximum coordination number of carbon in (c) Assertion is true but Reason is false.
commonly occurring compounds is 4, whereas that (d) Both Assertion and Reason are false.
of silicon is 6. This is due to (AIPMT 1994) 11. The colour imparted by Co(II) compounds to glass is
(a) availability of low lying d-orbitals in silicon (AIIMS 2006)
(b) large size of silicon (a) green (b) deep-blue
(c) more electropositive nature of silicon (c) yellow (d) red
(d) both (b) and (c). 12. The number of isomers possible for disubstituted borazine,
5. Aluminium (III) chloride forms a dimer because B3N3H4X2 is: (AIPMT 2006)
Aluminium (AIPMT 1995) (a) 3 (b) 4
(a) belongs to 3rd group (c) 6 (d) 2
(b) can have higher coordination number 13. Which glass will not crack when temperature changes ?
(DUMET 2006)
(c) cannot form a trimer
(a) Pyrex (b) Boron silicate
(d) has high ionization energy.
(c) Calcium silicate (d) Flint
6. Boron compounds behave as Lewis acids, because of
14. Value of x in potash alum, K2SO4.Alx (SO4)3 . 24H2O is
their (AIPMT 1996)
(CPMT 2007)
(a) ionisation property
(a) 4 (b) 1
(b) electron deficient nature
(c) 2 (d) None of these
(c) acidic nature
(d) covalent nature.
p-BLOCK (GROUP 13 AND 14) 71

15. In borax bead test which compound is formed? 23. The stability of +1 oxidation state increases in the
(Punjab PMET 2007) sequence (AIPMT 2009)
(a) Ortho borate (b) Meta borate (a) Al < Ga < In < Tl (b) Tl < In < Ga < Al
(c) Double oxide (d) Tetra borate (c) In < Tl < Ga < Al (d) Ga < In < Al < Tl
16. For which one of the following minerals, the composition 24. The lead of the lead pencils melts at (AIIMS 2009)
given is incorrect? (Kerala CEE 2007) (a) 2000ºC (b) 350ºC
(a) Glauber’s salt – Na2SO4. 10H2O (c) 3170ºC (d) 75ºC
(b) Borax – Na2B4O7.7H2O 25. Which amont the following is not a borane?
(c) Cornallite – KCl.MgCl2. 6H2O (AMU 2009)
(d) Soda ash – Na2CO3 (a) B2H6 (b) B3H6
17. Litharge is chemically (AIIMS 2007) (c) B4H10 (d) None of these
(a) PbO (b) PbO2 26. Darkening of surface painted with white lead is due to
(c) Pb3O4 (d) Pb(CH3COO)2 (CPMT 2009)
18. Supercritical CO2 is used as (AIIMS 2007) (a) H2S (b) CO2
(a) dry ice. (c) Cu (d) O2
(b) firefighting. 27. The main reason that SiCl 4 is easily hydrolyzed as
(c) a solvent for extraction of organic compounds from compared to CCl4 is that (Kerala CEE 2009)
natural sources. (a) Si—Si bond is weaker.
(d) a highly inert medium for carrying out various reactions. (b) SiCl4 can form hydrogen bonds.
19. White lead is (CPMT 2007) (c) SiCl4 is covalent.
(a) Pb3O4 (d) Si can extend its coordination number beyond four.
(b) PbO 28. Silica is soluble in (Haryana PMT 2009)
(c) 2PbCO3 . Pb(OH)2 (a) HCl (b) HNO3
(d) Pb(CH3COO)2 . Pb(OH)2 (c) H2SO4 (d) HF
20. Product of the following reaction is Al 4 C3  D 2 O  29. The tendency of BF3, BCl3 and BBr3 to behave as Lewis
acid decreases in the sequence (AIPMT 2010)
(PMT 2008)
(a) BF3 > BCl3 > BBr3 (b) BCl3 > BF3 > BBr3
(a) Al(OD)3 + CD4 (b) Al(OD)2 + CD4
(c) BBr3 > BCl3 > BF3 (d) BBr3 > BF3 > BCl3
(c) Al(OD)4 + CD4 (d) Al(OD)3 + CD
30. The strongest Lewis acid among boron halides is
21. Which of the following is used for making optical
instruments? (AFMC 2008) (RPMT 2010)
(a) SiO2 (b) Si (a) BBr3 (b) BCl3
(c) SiH4 (d) SiC (c) BI3 (d) BF3
22. Assertion: Coloured cations can be identified by borax 31. BF3 is (RPMT 2010)
bead test. (a) electron-deficient compound
Reason: Transparent bead (NaBO 2 + B 2 O3 ) forms (b) Lewis base
coloured bead with coloured cation. (AIIMS 2009) (c) used as rocket fuel
(a) Both Assertion and Reason are true and Reason is the (d) ionic compound
correct explanation of Assertion. 32. Borax is used as a cleansing agent because on dissolving
(b) Both Assertion and Reason are true but Reason is not in water, it gives (RPMT 2010)
the correct explanation of Assertion. (a) alkaline solution (b) acidic solution
(c) Assertion is true but Reason is false. (c) bleaching solution (d) amphoteric solution
(d) Both Assertion and Reason are false.
72 p-BLOCK (GROUP 13 AND 14)

33. Inorganic benzene is (PMT 2010) 41. The basic structural unit of silicates is (NEET 2013)
(a) B3H3N3 (b) BH3NH3 (a) SiO– (b) SiO 44
(c) B3N3H6 (d) H3B3N6 2
(c) SiO 3 (d) SiO 24
34. Chemical formula of phosgene is (AFMC 2010)
42. Boric acid is an acid because its molecule
(a) COCl2 (b) CaOCl2
(NEET 2016)
(c) CaCO3 (d) COCl
(a) gives up a proton
35. Graphite is a good conductor of electricity. Its electrical
(b) accepts OH– from water releasing proton.
conductivity is due to the fact that (CPMT 2010)
(c) combines with proton from water molecule.
(a) it is an allotrope of carbon.
(d) contains replacable H+ ion.
(b) it has C-atoms arranged in large plates of rings of
strongly bound C-atoms. 43. The element Z = 114 has been discovered recently. It will
belong to which of the following family/group and
(c) in it C-atoms are sp2 hybridised.
electronic configuration ? (NEET 2017)
(d) it is a non-crystalline substance. 14 10 2 2
(a) Carbon family, [Rn]5f 6d 7s 7p
36. Which of the following is not attacked by hot sodium
(b) Oxygen family, [Rn]5f146d107s27p4
hydroxide solution? (Manipal 2010)
(c) Nitrogen family, [Rn]5f146d107s27p6
(a) Silicon (b) Carbon
(d) Halogen family, [Rn]5f146d107s27p5
(c) Tin (d) Lead
44. It is because of inability of ns2 electrons of the valence
37. Which type of silicate is shown in the given figure
shell to participate in bonding that (NEET 2017)
(Guj. CET 2010)
(a) Sn2+ is oxidizing while Pb4+ is reducing.
(b) Sn2+ and Pb2+ are both oxidizing and reducing.
(c) Sn4+ is reducing while Pb4+ is oxidizing.
(d) Sn2+ is reducing while Pb4+ is oxidizing.
45. MF63 , Which one of the following elements is unable to
form ion? (NEET 2018)
(a) Al (b) B
(c) Ga (d) In
46. The correct order of atomic radii in group 13 elements is
(NEET 2018)
(a) Orthosilicate (b) Pyrosilicate (a) B < Al <Ga< In <Tl (b) B <Ga< Al <Tl< In
(c) Meta silicate (d) None of these (c) B < Al < In <Ga<Tl (d) B <Ga< Al < In <Tl
38. Which of the following is not hydrolysed easily? 47. Which of the following is incorrect statement?
(OJEE 2010) (NEET 2019)
(a) CCl4 (b) SiCl4 (a) SnF4 is ionic in nature
(c) GeCl4 (d) SnCl4 (b) PbF4 is covalent in nature
39. Name the type of the structure of silicate in which one (c) SiCl4 is easily hydrolysed
oxygen atom of [SiO4]4– is shared? (AIPMT 2011) (d) GeX4 (X = F, Cl, Br, I) is more stabled than GeX2.
(a) Three dimensional (b) Linear chain silicate 48. Which of the following species is not stable?
(c) Sheet silicate (d) Pyrosilicate (NEET 2019)
40. Which of the following structure is similar to graphite? (a) [SiCl6]2- (b) [SiF6]2-
(NEET 2013) (c) [GeCl6]2- (d) [Sn(OH)6]2-
(a) BN (b) B
(c) B4C (d) B2H6
p-BLOCK (GROUP 13 AND 14) 73
49. Which of the following compounds is used in cosmetic
surgery? (Odisha NEET 2019)
(a) Silica (b) Silicates
(c) Silicones (d) Zeolites
50. Identify the correct statements from the following:
(NEET 2020)
(A) CO2(g) is used as refrigerant for ice-cream and frozen
food.
(B) The structure of C60 contains twelve six carbon rings
and twenty five carbon rings.
(C) ZSM-5, a type of zeolite, is used to convert alcohols
into gasoline
(D) CO is colourless and odourless gas.
(a) (A), (B) and (C) only
(b) (A) and (C) only
(c) (B) and (C) only
(d) (C) and (D) only
74 p-BLOCK (GROUP 13 AND 14)

EXERCISE - 3: Achiever’s Section

1. The blue coloured mineral ‘Lapis Lazuli’ which is used (a) (A)  (iv), (B)  (ii), (C)  (i), (D)  (iii)
as a semi-precious stone is a mineral of the following
class: (b) (A) (iv), (B)  (i), (C)  (ii), (D)  (iii)

(a) sodium alumino silicate (c) (A)  (ii), (B)  (i), (C)  (iii), (D)  (iv)

(b) zinc cobaltate (d) (A)  (i), (B)  (ii), (C)  (iii), (D)  (iv)

(c) basic copper carbonate

Assertion-Reason Type Questions
(d) prussian blue
2. A metal X reacts with aqueous NaOH solution to form Y While answering these questions, you are required to choose
and a highly inflammable gas. Solution Y is heated and any one of the following four responses.
CO2 is poured through it. Z precipitates out and Na2CO3 (A) If both Assertion and Reason are correct and the Reason is
is formed. Z on heating gives Al2O3, Identify X, Y and Z. a correct explanation of the Assertion.
(B) If both Assertion and Reason are correct but Reason is not
X Y Z
a correct explanation of the Assertion.
(a) Al NaAlO2 Al(OH)3 (C) If the Assertion is correct but Reason is incorrect.
(D) If the Reason is correct but Assertion is incorrect.
(b) Al2O3 NaAlO2 Al2CO3
6. Assertion : Al(OH)3 is amphoteric in nature.
(c) Al2O3 [Na2AlO2]+OH– Al(OH)3
Reason : Al—O and O—H bonds can be broken with
(d) Al Al(OH)3 Al2O3 equal ease in Al (OH)3.
(a) A (b) B
3. When an inorganic compound (X) having 3C—2e as
well as 2c—2e bonds reacts with ammonia gas at a cer- (c) C (d) D
tain temperature, gives a compound (Y), isostructural
with benzene. Compound (X) with ammonia at a high 7. Assertion : BF3 is a weaker Lewis acid than BCl3.
temperature produces a substance (Z). Which of the Reason : BF3 molecule is stabilized to a greater extent
following is not correct? than BCl3 by B—F -bonding.
(a) (X) is B2H6
(a) A (b) B
(b) (Z) is known as inorganic graphite
(c) C (d) D
(c) (Y) is B3N3H6 (d) (Z) is soft like graphite
4. Which of the following is not matched correctly with its 8. Assertion : AlF3 is soluble in KF but addition of BF3
use ? brings its precipitation.

(a) Piezoelectric material - Quartz Reason BF3 is more acidic than AlF3.

(b) Ion-exchangers - Graphite (a) A (b) B

(c) Filtration platns - Silica (c) C (d) D

(d) Electrical insulators - Silicones 9. Assertion : Boron always forms covalent bond.

5. Match the column I with column II and mark the Reason : The small size of B3+ favours formation of co-
appropriate choice. valent bond.
(a) A (b) B
Column I Column II
(c) C (d) D
(A) Galena (i) Abrasive
10. Assertion : Boron is p block element.
(B) Diamond (ii) Metal carbonyls Reason : Last electron entres in p sub shell.
(C) Carbon monoxide (iii) Hydrides of Si (a) A (b) B
(D) Silanes (iv) An ore of lead (c) C (d) D
p-BLOCK (GROUP 13 AND 14) 75
11. Assertion : In water, orthoboric acid behaves as a weak 18. Assertion : If aluminium atoms replace a few silicon at-
monobasic acid. oms in three dimensional network of silicon dioxide, the
Reason : In water, othoboric acid acts as a proton donor. overall structure acquires a negative charge.
(a) A (b) B Reason : Aluminium is trivalent while silicon is tetrava-
(c) C (d) D lent.
12. Assertion : Borax bead test is not suitable for Al (III) (a) A (b) B
Reason : Al2O3 is insoluble in water. (c) C (d) D
(a) A (b) B
(c) C (d) D Comprehension Based Typed Questions
13. Assertion : In water, orthoboric acid behaves as a weak
monobasic acid.
Passage (Ques 19 to 24)
Reason : In water, orthoboric acid acts as a proton donor. Aluminium is stable in air and water in spite of the fact that it is
(a) A (b) B reactive metal. The reason is that a thin film of its oxide is formed
on its surface which it passive for further attack. The layer is so
(c) C (d) D
useful that in industry, it is purposely deposited by an electro-
14. Assertion : Pb4+ compounds are stronger oxidising lytic process called anodising
agents than Sn2+ compounds. Reaction of aluminium with oxygen is highly exothermic and is
Reason : The higher oxidation states for the group 14 called thermite reaction.
elements are more stable for the heavier members of the
group due to ‘inert pair effect’. 3
2Al(s) + O 2 (g)  Al 2 O3 (s); ΔH = –1670 kJ
(a) A (b) B 2
(c) C (d) D Thermite reaction finds applications in the metallurgical extrac-
15. Assertion : Between SiCl4 and CCl4, only SiCl4 reacts tion of many metals from their oxides and for welding of metals.
with water. The drawback is that to start the reaction, high temperature is
required for which an ignition mixture is used.
Reason : SiCl4 is ionic and CCl4 is covalent.
(a) A (b) B
(c) C (d) D 19. Anodising can be done by electrolysing dilute H2SO4
with aluminium as anode. This results in :
16. Assertion : SiF62 is known but SiCl 62 is not. (a) the formation of Al 2(SO 4 ) 3 on the surface of
Reason : Size of fluorine is small and its lone pair of aluminium anode
electrons interacts with d-orbitals of Si strongly. (b) the formation of oxide film (Al2O3) on the surface of
aluminium anode
(a) Both Assertion and Reason are true and Reason is
(c) the formation of polymeric aluminium hydride film
the correct explanation of Assertion. on the surface of aluminium anode
(b) Both Assertion and Reason are true but Reason is (d) none of the above
not the correct explanation of Assertion.
20. The reaction which is not involved in thermite process:
(c) Assertion is true but Reason is false.
(d) Both Assertion and Reason are false. (a) 3Mn 3 O 4  8Al 
 9Mn  4Al2 O3
17. Assertion : PbI4 is a stable compound. (b) Cr2 O 3  2Al 
 2Cr  Al2 O3
Reason : Iodide stabilizes higher oxidation state.
(c) 2Fe  Al 2 O 3 
 Fe 2 O 3  2Al
(a) Both Assertion and Reason are true and Reason is
(d) B 2 O3  2Al 
 2B  Al 2 O3
the correct explanation of Assertion.
(b) Both Assertion and Reason are true but Reason is 21. Thermite a mixture used for welding is:
not the correct explanation of Assertion. (a) Fe and Al (b) BaO and Mg powder
(c) Assertion is true but Reason is false. (c) Cu and Al (d) Fe2O3 and Al powder
(d) Both Assertion and Reason are false.
76 p-BLOCK (GROUP 13 AND 14)
22. Anodised aluminium is : 26. Compound (B) is:
(a) Al obtained at anode (a) NaBO2 (b) Na2B4O7
(b) Al prepared electrolytically (c) Na3BO3 (d) NaOH
(c) alloy of Al containing 95% Al 27. Compound (C) is:
(d) Al electrolytically coated with aluminium oxide (a) H2B4O7 (b) HBO2
23. Which one of the following metals cannot be extracted (c) H3BO3 (d) HB3O5
by using Al as a reducing agent? 28. Compound (D) is:
(a) Na from Na2O (b) Cr from Cr2O3 (a) H3BO3 (b) B2O3
(c) W from WO3 (d) Mn from Mn3O4 (c) B (d) none of these
24. Aluminium becomes passive in: 29. Compound (E) is:
(a) conc. HNO3 (b) H2CrO4 (a) Cu2O (b) CuS
(c) HClO4 (d) all of these (c) CuSO3 (d) Cu(BO2)2

Passage (Ques. 25 to 29) Passage (Ques. 30 )

Fused
Ca 2 B6 O11  Na 2 CO3  (A)  (B)  CaCO3 700 o C
(i) Boron  O 2     (X )

(A)  CO 2 
(B)  Na 2 CO3
Solution (ii) (X)  C(carbon)  Cl2  (Y)  CO
H O
2  Acid (C) (iii) (Y)  LiAlH 4  (Z)  LiCl  AlCl3
(B)  Conc.HCl 
 NaCl  Acid 

Strongly (iv) (Z )  NH 3  (A )  H

eat
 (B)
(C) (D)
heated
Heated
(v) (Z)  NaH  (D)
(D)  CuSO 4  Blue
 coloured (E) compound
inflame
30. Compound (Z) is:
(a) an ionic compound
25. Compound (A) is:
(b) an electron rich compound
(a) NaBO2 (b) Na2B4O7
(c) Na3BO3 (d) NaOH (c) 3C—2e compound
(d) having ethane like structure
p-BLOCK (GROUP 13 AND 14) 77

Notes:

Find Answer Key and Detailed Solutions at the end of this book

p-BLOCK (GROUP 13 AND 14)

 15
ENVIRONMENTAL
CHEMISTRY
Chapter 15

Enviornmental Chemistry

1. Introduction 2. Environmental Pollution

Environmental studies deal with the sum of all social, economical, Environmental pollution is an undesirable change in physical,
biological, physical and chemical interrelations with our chemical or biological characteristics of our surroundings (air, water
surroundings. In this unit the focus will be on environmental or land). It can affect human, animal and plant life as well as materials.
chemistry.The branch of science which deals with the chemical Pollution may be natural or man made. It can be classified according
phenomena occurring in the environment is called as environmental to the components of environment being damaged. These are :
chemistry. (i) Air pollution
The environment means surroundings. It has 4 following (ii) Water pollution
component: (iii) Soil (land) pollution
1.1 Atmosphere
1.1.1 Function of the Atmosphere 2.1 Environmental Pollutant
(i) It contain all the gases which are essential for the life on the
When the concentration of a substance already present in nature
earth.
or of a new substance increases to undesirable proportions
(ii) It is a carrier of water vapour which are needed for all life. causing danger to human beings, other animals or vegetation and
(iii) O3 is present in it which absorbs harmful U.V. radiations. other materials, the substance is treated as a pollutant. The
(iv) It maintain heat balance of the earth by absorbing infrared pollutants spoil the environment and are harmful to living
radiation coming from the sun and remitted from the earth. organisms and other materials. The common pollutants are :
1.1.2 Regions (or Structure) of the Atmosphere (i) gases like carbon monoxide, sulphur dioxide, oxides of
It has 4 region. These regions are defined by the temperature. nitrogen, etc.

Table. 15.1: Regions of atmosphere (ii) compounds of metals like lead, mercury, zinc, cadmium,
arsenic, etc.
Name of Height Temperature Main constituents
region in Kms. in °C (iii) pollen grains, dust
Troposphere 0.11 15 to - 56 N2, O2, CO2, H2O (iv) pesticides and detergents
Stratosphere 11 - 50 –56 to - 2 O3, O2 (v) sewage and
Mesophere 50 - 90 – 2 to – 92 N2 + O2 (vi) radioactive substances
Thermosphere 90 – 500 –92 to –1200 O2, O+, NO+
2.1.1 Primary and Secondary Pollutants
(i) Primary pollutants : Those which after their formation enter
1.2 Hydrosphere (75% of Earth)
the environment and remain as such. ex. : NO, NO2 , SO2.
The part which contain water in the form of sea, oceans, reivers,
(ii) Secondary pollutants : The harmful material which are
lakes, ponds.
formed by chemical reaction between primary pollutants in
the atmosphere. ex.
1.3 Lithosphere hv
Hydrocarbon  Oxideof nitrogen  compound
It is solid component of the earth consisting of soil, rocks,
mountains. 2.1.2 Bio Degradable and Non Bio Degradable
Pollutants
1.4 Biosphere (i) Bio-degradable pollutants : The materials (such as cow
dungs) which are easily decomposed by the micro-organism.
It is the part of the lithosphere, hydrosphere and atmosphere.
Thus are not harmful, but in the excess in environment, they
Where living organism interact with these parts and lived together.
do not undergo degradation completing and thus become
pollutant.

SCAN CODE
Enviornmental Chemistry
80 ENVIRONMENTAL CHEMISTRY

(ii) Non-biodegradable pollutants : The material (such as Hg, 3.2 Global Warming and Greenhouse
Al, DDT) which do not undergo degradation (or degrade
very slowly) but their presence even in very small amount Effect
in the environment is very harmful. They may react with Gases such as CO2 , NO2, CFCs (chloro fluorocarbons) allow sun
other compounds present in the environment and produce rays to pass through them but then absorb and reradiate the heat
more toxic compound. back towards the earth. These are therefore termed as green house
gases.
Radiations (ultra violet) from the sun penetrate the earth’s
3. Atmospheric Pollution atmosphere and reach earth. The surface of earth partially absorbs
the radiations. The rest is re-radiated as infrared radiation from
Atmospheric pollution is generally studied as tropospheric and
the earth’s surface. In polluted air, molecules of CO2 , CH4 , CFCs,
stratospheric pollution. The presence of ozone in the stratosphere
N2O, O3 and water vapours are present. These gases can absorb
prevents about 99.5 per cent of the sun’s harmful ultraviolet (UV)
infrared radiations but cannot absorb the ultra violet radiations.
radiations from reaching the earth’s surface and thereby protecting
Energy of these trapped radiations raise the temperature of earth
humans and other animals from its effect.
and its atmosphere. Thus if proportion of green house gases
increases in the atmosphere heat trapped by them will raise the
3.1 Tropospheric Pollution temperature of the earth and will cause global warming. Greenhouse
effect leading to global warming shall have severe effects on
The tropospheric pollution occurs because of the presence of rainfall, sea level, plant and animal growth.
undesirable solid or gaseous particles in air. The pollutants may
be broadly classified into two major types : 3.2.1 Harmful Effect of Global Warming
1. Gaseous air pollutants : These include oxides of sulphur, (i) Rise in sea level: Polar ice caps would melt because of rise
nitrogen and carbon, hydrogen sulphide, hydrocarbons, in temperature and add more water to sea. Moreover water
ozone and other oxidants. expands when it heats up. This will lead to rise of sea level.
It will flood the low lying coastal area and many cities will
2. Particulate pollutants : These are dust, fumes, mist, spray,
get submerged in water.
smoke etc.
(ii) Drought: warming will result in 10% decrease in precipitation
Table. 15.2: Major Air Pollutants their Sources and
(rain fall) and this will decrease rain fall causing drought
Effects conditions.
Major Pollutants Sources Effects (iii) Effect on plant and animals: Drought will reduce
of Air photosynthesis in plants and lead to reduced growth of
SO2 Vehicular Irritation to the eyes, plants.Warmer conditions will encourage growth of pests.
combustion, fossil acid rain premature
(iv) Increase in CO2 : Warmer conditions accelerate microbial
fuel burning falling of leaves
degradation of organic matter and add more CO2.
CO and CO2 Vehicular Global warming,
combustion and green house effect,
burning of fuels and CO has great affanity 3.3 Acid Rain
hydrocarbons for haemoglobin and Acid rain containg H2SO4, HNO3 (and small amount of HCl) which
forms the carboxy are formed from the oxide S and N2 present in the air is called as
haemoglobin acid rain. The pH of acid rain is 4-5.
Smoke, fly ash and Thermal power Respiratory diseases
soot station
3.3.1 Foramtion of Acid Rain
Lead and mercury Auto exhaust from Affects the nervous Formation of acid rain : The oxide of nitrogen undergo oxidation
gasoline, paints, system and reaction. The reaction with the water vapour present in the
strorage batteries, circulatory system atmosphere to form HNO3.
fossil fuel burning causing nerve and
brain damage
CFCs Refrigerants and Kidney damage and
aerosol ozone deplection

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Step (I) : 3.4 Particulates Pollutants

hv
NO  O3   NO 2  O 2 The small sized solid particles and liquid droplets which range in
NO  O  hv
 NO  O size from 2 × 10–10 m (0.0002 m) to 5 × 10–4 m are collectively
2 3 3 2

hv called as particulates. These particles are usually individually not

NO 2  NO3   N 2 O5 visible to the naked eye. However, small particles often collectively
N O  H O  hv
 2HNO form a haze that restricts the visibility. The common particulates
2 5 2 3
are smoke, mists, fumes, dust etc.
HNO3 come down with rain to earths.
The particulates in the atmosphere may be viable or non-viable.
Step (II) :
The viable particulates are the small living organisms which are
The SO3 reacts with water vapour and formed H2SO4.
dispersed in the atmosphere. These includes bacteria, moulds,
2SO 2  O 2 
 2SO3 fungi, algae, etc. Some of these viable particulates cause allergic
reactions on human beings. Fungi can also cause plant diseases.
The HNO3 and H2SO4 combine with HCl present in the air to
produce acidic precipitation which is called as acid rain. Non-viable particulates are formed either by the breakdown of
large materials or by the condensation of minute particles and
In acid rain H2SO4 = 60 - 70%
droplets.
HNO3 = 30 - 40 %
There are four types of non-viable particulates in the atmosphere:
HCl = Very small amount
(i) Mists are produced by particles of spray liquids and the
NOTE : condensation of vapours in air. Examples are portions of
The normal rain water has a pH about 5.6 due to dissolution of herbicides and insecticides that miss their targets and travel
CO2 in water. through the air to form mists.
CO 2  H 2 O  H 2 CO 3  2H   CO32 (ii) Smoke denotes very small soot particles produced by
burning and combustion of organic matter. Oil smoke,
When pH of rain water become less than 5.6 it will be acidic. tobacco smoke and carbon smoke are typical examples of
this type of particulate emission.
3.3.2 Harmfull Effect of Acid-Rain (iii) Fumes are condenses vapours : fumes of metals are the
(i) It damage to building and status which contain marble, lime well-known particulates of this type. Examples of this
stone, state, mortar etc. category also include metallurgical fumes and alkali fumes.
(iv) Dust consists of the particles produced during crushing,
CaCO 3  H 2SO 4 
 CaSO 4  H 2 O  CO 2 grinding and attribution of solid materials. Non-viable dust
(ii) It damage iron and steel structure. particulates in the atmosphere consist of ground limestone,
(iii) It corrodes water pipe, so heavy metal (like Fe, Pb, Cu) are sand tailings from floatation, pulverised coal, cement, fly
mixed with water which have toxic effect. ash and silica dust.
(iv) The acid rain increase the acidity of the lake. Which is The effects of particulate pollutants depend upon the size of the
harfmful to fishes. particles. The coarser particles of size more than 5 microns are
likely to lodge in the nasal passages whereas the smaller ones are
(v) It damage the trees, plants and retards the grwth of the
more likely to penetrate into the lungs. The rate of penetration is
plant.
inversely proportional to the size of the particles. Some of these
NOTE : particles are carcinogens. Continuous inhaling of these small
Acid rain reacts with marble, CaCO3 of Taj Mahal particles for long periods of time irritates the lungs and causes
(CaCO3 +H2SO4  CaSO4 + H2O + CO2) causing damage to ‘scarring’ or ‘fibrosis’ of the lung lining. This type of disease is
this wonderful monument that has attracted people from very common in industrial settings and is known as
around the world. As a result, the monument is being slowly “pneumoconiosis”.
disfigured and the marble is getting discoloured and lustreless.

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3.5 Smog 3.5.3 Effects of Photochemcial Smog

Smog is a mixture of smoke, dust particles and small drops of fog. (i) It can cause coughing, wheezing bronchial constriction and
It is a major air pollutant in big cities.Smog is of two types : Peroxyaetyl nitrates and aldehydes found in smog are eye
irritants.
3.5.1 Classical Smog
(ii) Materials are also adversely affected by some smog
This type of smog is formed by the combination of smoke, dust and
components.
fog containing sulphur dioxide from polluted air. This is also called
(iii) Smog also affects to cause damage to vegetation and
chemical smog. Chemically, it is a reducing mixture so it is also called
reduction in plant growth and crop productivity.
reducing smog.
(iv) PAN has the highest toxicity to plants, attacking younger
3.5.2 Photochemcial Smog
leaves and causing 'bronzing' and 'glazing' of their surfaces.
This type of smog is formed by the combination of smoke, dust
3.5.4 Control of Photochemical Smog
and fog with an air pollutant in the atmosphere as a result of
photochemical reaction. Installation of efficient catalytic converters in the automobiles is
the most straightforward way of reducing smog formation as it
The chemistry of formation of photochemical smog centres
prevents the release of nitrogen oxides and hydrocarbons to the
around nitric oxide (NO). The formation of photochemical smog
atmosphere.
can be understood by the following steps :
(i) During the early morning before the sun rise, the automobile
exhaust emits CO, hydrocarbons and oxides of nitrogen. The
NO reacts with oxygen to produce NO2, a yellowish brown gas.
4. Depletion of Ozone Layer
(ii) As the sun rises, ultra-violet and visible radiations fall on Ozone is an important constituent of the stratosphere at altitudes
the earth. The ultra-violet rays convert NO2 back to NO and between 15 and 25 km. It is formed in the atmosphere by the
decomposition of oxygen by ultra-violet radiation from the sun
produce highly reactive atoms of oxygen.
having wavelength shorter than 260 nm.
NO2  u.v.Radiation  NO  O
(Re active Oxygen) O 2  g   hv 
u.v
 O g  O g 
Some of these oxygen atoms combine with O2 in the air to produce O  g   O2  g  
u.v
O3  g 
ozone gas.
It is thermodynamically unstable and decomposes into molecular
O 2  O  O3 oxygen. It has the important photochemical property of absorbing
solar radiation between the wavelength of 200 nm and 300 nm.
Ozone reacts with NO to form NO2 and O2
O3  NO  NO 2  O 2 O3  g   hv  O  g   O 2  g 
The reactive atomic oxygen formed in the above reaction
NO2 again absorbs u.v. radiations and the entire cycle starts again.
recombines with molecular oxygen to form ozone. This completes
Both NO2 and O3 are strong oxidizing agents and can react with
the ozone cycle.
unburnt hydrocarbons (from exhaust of automobiles) to form organic
Thus, a dynamic equilibrium exists between the production and
free radicals. The formation of organic free radicals results into a
decomposition of ozone molecules.
number of chain reactions producing many undesirable compounds
(such as formaldehyde, acrolein, organic peroxides, organic The thick layer of ozone is called ozone blanket because it is very
hydroperoxides, peroxyacyl nitrates etc.) which constitute effective in absorbing harmful ultra violet rays given out by the
sun. Therefore, the ozone layer is also known as protective shield.
photochemical smog. It also includes H2O2. The brownish haze of
Recently in 1980, scientists have observed a hole in the ozone
photochemical smog is largely due to brown colour of NO2.
blanket covering the upper atmosphere around Antarctica. Recent
3CH 4  2O3  3HCHO  3H 2 O observations have also shown that the ozone layer diminishes over
Acrolein and peroxyacetylnitrate (PAN) are very noxious the south pole in spring during August-September to a greater
substances. extent year after year. This depletion of the protective blanket of
ozone will cause a damaging effect because harmful ultra-violet
rays can reach earth through this hole. The increased level of ultra-
violet rays will result in damage to plants, animals, human beings
and even matter posing great threat to ecosystem over the globe.

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Thus, the depletion of ozone layer is a serious threat to mankind.

The depletion of ozone may be due to some natural processes or
5. Water Pollution
industrial activities. The quality of drinking water is very important for human welfare.
The pollution of water by sewage has been linked to the spread of
The main cause of depletion of ozone layer is its reaction with
diseases such as cholera and typhoid fever. Table lists the major
chlorofluorocarbons. Unlike other chemicals, chlorofluorocarbons
water pollutants, their sources and effects:
are not removed from the atmosphere by usual scavenging
processes like photo dissociation, oxidation, rainfall, etc. As a In addition, industrial wastes also contaminate water:
result they move to stratosphere by random diffusion. Then these (i) Heavy Metals : Metals such as Cd, Pb and Hg may be present
are destroyed by photolysis and release atomic chlorine. This in industrial or mining waste. Cadmium and mercury can
released Cl atoms cause a catalytic chemical reaction and cause cause kidneys, liver brain and central nervous system.
significant depletion of stratospheric ozone layer. (ii) Detergents and Fertilizers : These may contain phosphates

Cl 2 CF2  hv  Cl  ClCF as additives. The addition of phosphours to water, in the
2
form of the phosphate anion PO43–, encourages the formation
The free radical, Cl• reacts with O3 through a chain reaction
of algae, which reduces the dissolved oxygen concentration
Cl  O3  ClO   O 2 of water. The process, known as eutrophication, impedes
ClO  O  Cl  O 2 the development of higher life forms, such as fish.
These chlorine atoms are free to react with more ozone. As a (iii) Acid-polluted water (pH < 3) : Water downstream from a
result, many O3 molecules can be destroyed for each chlorine mine may be contaminated by acid mine drainage, the result
atom produced. It has been shown that over one thousand ozone of microbial oxidation of discarded waste material at the
molecules can be destroyed by one Cl. mine site. Acid mine water principally contain sulphuric acid
produced by the oxidation of iron pyrites (FeS2). Industrial
The net result of these reactions is destruction of several
wastes and acid rain may also contribute to the acidity of
molecules of O3 for each Cl atom produced.
natural waters.

Table. 15. 3: Major Water Pollutants their Sources and Effects

Pollutant Sources of Pollutants Effects and Significance
Pathogens Sewage, human and animal wastes, natural Depletion of dissolved oxygen in water (foul
and urban runoff from land, industrial waste odour) health effects (outbreaks of water born
diseases)
Organic pollutants Automobile and machine waste, tanker spills, Disruption of marine life, aesthetic damage
 Oil and grease offshore oil leakage Chemicals used for bet- Toxic effects (Harmful for aquatic life), possible
ter yield from agriculture
 Pesticides and weedicides genetic defects and cancer ; kills fish Eutrophi-
 Plastics cation, aesthetics
 Detergents
Inorganic pollutants Fertilizers
Agricultural runoff Algal bloom and eutrophication, nitrates cause
(phosphates and nitrates)
methemoglobenemia

Acids and alkalies Mine drainage, industrial wastes, natural and Kill fresh water organisms, unfit for drinking,
urban runoff irrigation and industrial use.

Radioactive materials Natural sources, uranium mining and process- Cancer and genetic defects
ing, hospitals and research laboratories
using radioisotopes
Heat Cooling water for industrial, nuclear and ther- Decreases solubility of oxyegn in water, dis-
mal plants rupts aquatic ecosystems
Sediments Natural erosion, runoff from agricultual land Affects water quality, reduces fish population
and construction sites

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(iv) Polychlorinated biphenyls (PCBs) : These chemicals are Other Metals : The maximum recommended levels of common
relatively recent additions to the list of contaminants of metals in drinking water are as follows:
water. Having high stabilities, PCBs find many applications, Table. 15.4: Maximum Prescribed Concentration of
for example they are used as fluids in transformer capacitors.
Some Metals in Drinking Water
PCBs are resistant to oxidation and their release into the
environment causes skin disorders in humans. They are Metal Maximum concentration
reported to be carcinogenic. (ppm or mg dm-3)
Biochemical Oxygen Demand (BOD) : The polluted water may Fe 0.2
Mn 0.05
contain large amounts of inorganic and organic compounds. Some
Al 0.2
of these can be oxidised by dissolved oxygen in the presence of Cu 3.0
microorganisms. Biochemical oxygen demand (BOD) is a measure Zn 5.0
of the dissolved oxygen that would be needed by the Cd 0.005
microorganisms to oxidise these compounds. BOD, therefore, is a
measure of the contamination caused by the totality of those
compounds which can be oxidised in the presence of
6. Soil Polluion
microorganisms. They, therefore, don;t contribute to the BOD, Most of the land pollution is caused by pesticides and other
tough their presence makes water unfit for consumption. The chemicals which are added to the soil grow better crops. Often, a
BOD is taken as a realistic measure of water quality 'clean water' pesticide poisons many more organisms than those intended.
would have a BOD value of less than 5 ppm whereas highly Some of these poison pass through food chains and eventually
polluted river water could have a BOD value of 17 ppm or more. reach harmful proportions. Solid wastes are another cause of soil
(land) pollution.

5.1 International Standards for Drinking

6.1 Sources of Pollution
Water
1. Industrial waste: Industrial wastes are the major cause of
The quality of water is of vital concern for mankind since it is soil pollution because the wastes are toxic due to presence
directly linked with human welfare. There are some international of cyanides, chromates, acids, alkalies, metal like nickel,
standars for drinking water, which must always be obeyed if water cadmium, mercury and lead. Some industries like paper
is to be used for drinking purposes. These are : industries Sugar and textile mills, chemical industries &
Fluoride : Soluble fluoride is often added to drinking water to cement industries are also responsible for soil pollution.
bring it up to a concentration of 1 ppm or 1 mg dm–3. This The wastes of these industries are not bio-degradable.
concentration is within agreed safety limits and has been shown 2. Urban and domestic waste: The urban and domestic wastes
to protect teeth against decay. High concentrations of fluoride referred as soil refuse, containing garbage, and rubbish,
are poisonous and are harmful to bone and teeth at levels over 10 paper pieces, glass, plastics polythene bags, cans detergents
ppm (mg dm–3). and cakes. These substances emit.Toxic gases,
Lead : The limit for the concentration of lead ions in drinking hydrocarbons and pathogenic microbes cause to disease.
water is 50 ppb (g dm–3). If water is relatively acidic and lead pipes 3. Agricultural chemicals: The fertilizers, pesticides,
are used for water transport, then the water is liable to get herbicides insecticides and fungicides are commonly used
contaminated with lead. to save and increase the yield of crops but they have polluted
pH : The pH of drinking water should be between 5.5 and 9.5. A the soil. Some time the entry of these chemicals in food
decrease in the pH of the water increases the solubility of metal chain has cause to adverse effects on health of consumers.
ions. 4. Fertilizers: The fertilizers increase the yield crop it has no
Sulphate : Sulphate is harmless at moderate levles, but excessive doubt but the excessive use has adverse effects. It disturb
sulphate (> 500 ppm) is thought to have a laxative effect. the pH of soil, ionic balance and the presence of certain
Nitrate: Excess nitrate in drinking water can lead to elements. So they have a number of health hazards. The
methemoglobinemia (blue-baby syndrome). It also may be linked nitrites cause to cancer in human body.
to stomach cancer, although this link has not been proved. A
maximum limit of 50 ppm for the nitrate ion in drinking water has
been set.

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5. Pesticides: The chemicals are used to kill or to stop the (i) Swachh Bharat Mission–Urban (SBM–U): Primarily aims
growth of unwanted organisms and entry of these chemicals is making Urban India free from open defecation and
into food and water cause effect on the health of consumers. achieving 100% scientific management of solid waste in the
6. Insecticides: Some chemicals like DDT, BHC, aldrin, dieldrin country.
are used to kill the insects, the use of DDT is banned by the (ii) Swachh Bharat Mission Gramin (SBM–G): Its targets to
government because it is not biodegradable. Some bio bring about an improvement in the general quality of life in
degradable organ phosphates, carbonates may be used in rural areas by promoting cleanliness and hygiene, and
place of insecticides. eliminating open defecation.
7. Herbicides: The compounds used to control the growth of
weeds, some inorganic compounds like sodium chlorate and
sodium arsenite (Na 3AsO 3) were commonly used as 7.2 Collection and Disposal
herbicids. These one toxic in nature. So Now-a-days organic Domestic wastes are collected in small bins, then transferred the
herbicide Triazines are preferred. waste to community bins. From these community bins, these are
8. Fungicides: Fungicides are used to chock the growth of collected and carried to the disposable site. At the site, garbage is
fungi. Organic compounds of mercury have been used as sorted out and separated into biodegradable and non-
fungicides. Many people in Iraq resulted to death due to biodegradable materials. Biodegradable wastes are deposited in
eating breads made from grains that been treated with methyl land fills and are converted into compost. Non-biodegradable
mercury fungicide. materials such as plastic, metals, glass, etc. are sent for recycling.
The waste if not collected in garbage bins, finds its way into the
sewers. Some of it is eaten by cattle. Non-biodegradable wastes
6.2 Central of Soil Pollutions like polythene bag, glass, metal scraps, etc. choke the sewers and
The following steps have been suggested to control the soil cause inconvenience.
pollutioins: Therefore, all domestic wastes should be properly collected and
(i) The use of chemical fertilizers can be reduced by applying disposed. The poor management causes health problems leading
bio-fertilizers and manures. to epidemics due to contamination of ground water.
(ii) Re cycling and recovery of materials appears to be a
reasonable solution for reducing soil pollutions. Materials
like papers, gas and some kinds of plastics can be recycled. 8. Green Chemistry
(iii) Control of land loss can be attempted through restoring “Green chemistry is the design of chemical products and processes
forests and grass cover to check soil erosion and flood. that reduce or eliminate the use and generation of hazardous
(iv) Proper methods should be adopted for the disposal of solid substances.” Green chemistry is environment friendly, linking the
wastes. design of chemical products and processes with their impacts on
human health and the environment.

7. Strategies to Control 8.1 Principles of Green Chemistry

Environmental Pollution (i) The use of starting materials, reagents and solvents which
are less hazardous to man and his environment.
7.1 Waste Management (ii) More efficient use of raw materials.
The production and improper disposal of waste are causes for a (iii) Utilisation of chemical reactions which completely
great deal of environmental pollution. In addition to the household incorporate the starting materials in to final products and
waste which included sewage and municipal garbage, many toxic last amount of by product.
industrial wastes from manufacturing processes require treatment (iv) Search new alternatives which are environmental friendly.
and/or safe disposal. (v) It is better to prevent the waste than to treat or cleanup the
Under the mission ‘Swachh Bharat Abhiyan’ or ‘Clean India waste after it has been created.
Mission’ launched by the Government of India.Two programmes
are being implemented under this programme :

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8.2 Achievements of Green Chemistry (iv) ‘Green Solution’ to Clean Turbid Water: Powder of kernel
of tamarind seeds has been found to be an effective material
(i) Dry Cleaning of Clothes: Hydrogen peroxide (H2O2) gives
to clean municipal and industrial waste water. It is non-
better results and not harmful for bleaching of clothes in the
toxic, biodegradable and costeffective material. The present
laundary instead of tetrachloroethene (Cl2C=CCl2). This
practice is to use alum to treat such water. It has been found
compound is suspected to be carcinogenic and contiminated
that alum increases toxic ions in treated water and can cause
the ground water.
diseases.
(ii) Bleaching of Paper: Hydrogen peroxide (H2O2) is used with
catalyst for bleaching papers, instead of toxic chlorine gas.
(iii) Synthesis of Chemicals: Ethanal (CH 3CHO) is now
commercially prepared by one step oxidation of ethene in
the presence of ionic catalyst in aqueous medium with a
yield of 90%.
Catalyst
CH2  CH2  O2   CH3CHO  90%
Pd II  /Cu II in water

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Summary
 Environmental pollution: It is the effect of undesirable  Smog: Smoke is a mixture of smoke, dust particles and small
changes in our surroundings that have harmful effects on drops of fog.
plants, animals and human beings.  Biochemical Oxygen Demand (BOD): The amount of
 Major Environmental Pollutions are : oxygen required by bacteria to break down the organic matter
(i) Air pollution present in a certain volume of a sample of water.
(ii) Water pollution  Eutrophication: The process in which nutrient enriched
(iii) Soil pollution water bodies support a dense plant population, which kills
animal life by depriving it of oxygen and results in
 Green house effect: About 75% of the solar energy reaching
subsequent loss of biodiversity.
Earth is absorbed by the Earth’s surface, which increases
its temperature. The rest of the heat radiates back to the  Pesticides: These are organic compounds which are used
atmosphere. Some of the heat is trapped by gases such as to protect plants from pests.
carbon dioxide, methane, ozone, chlorofluorocarbon  Herbicides: They are used to kill weeds or undesirable
compounds (CFCs) and water vapour in the atmosphere. vegetation. Examples: sodium chlorate (NaClO3) and sodium
Thus, they add to heating of the atmosphere. This causes arsinite (Na3AsO3).
global warming.  Green chemistry: Green chemistry is a strategy to design
 Global warming: An increase in the average temperature of chemical processes and products which reduces or
the Earth’s atmosphere (especially a sustained increase that eliminates the use and generation of hazardous substances.
causes climatic changes) which may be caused by additional The chemical reactions should be such that the reactants
heat being trapped by the greenhouse gases. are fully converted into useful environmental friendly
products by using an environment friendly medium so that
no chemical pollutants introduced in the environment.

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Solved Examples
Example-1
Ans. (c)
Which of the following factors have harmful effect on our Sol. Particulate pollutants -These are dust mist, fumes smog,
environment ? smoke etc.,
(i) Environmental pollution Example-5
(ii) Natural environmental gases Sulphur dioxide causes:
(iii) Deforestation
I. respiratory diseases in human being
(iv) Uncontrolled birth rate II. Red haze in the traffic
(a) (i), (ii) and (iii) (b) (ii) and (iii) III. Irritation of the eyes.
(c) (i) and (iv) (d) (i), (iii) and (iv)
(a) I and II (b) II and III
Ans. (d)
(c) I and III (d) I, II and III
Sol. Factors causing harmful effect of environment are (i)
Ans. (c)
pollution (ii) increasing population, i.e., uncontrolled birth
Sol. Sulphur dioxide causes respiratory diseases in human
rate (iii) deforestation etc.,
being and irritation of the eyes.
Example-2
Example-6
Pollutants which are slowly degraded by natural process
Carbon monoxide gas is more dangerous than carbon
rapidly known as
dioxide gas. Why?
(a) Biodegradable pollutants
Sol. Carbon monoxide combines with haemoglobin to form a
(b) Non-Biodegradable pollutants
very stable compound known as carboxyhaemoglobin
(c) Both (a) and (b)
when its concentration in blood reaches 3-4%, the oxygen
(d) None of the above
carrying capacity of the blood is greatly reduced. This
Ans. (a)
results into headache, nervousness and sometimes death
Sol. Pollutants which are degraded by natural process rapidly
of the person. On the other had CO2 does not combine
are known as biodegradable pollutants.
with haemoglobin and hence is less harmful than CO.
Example-3
Example-7
The lowest region of atmosphere in which the human
Which gases are responsible for greenhouse effect? List
beings along with other organisms live is called…A… Here
some of them.
A refers to.
Sol. CO2 is mainly responsible for greenhouse effect. Other
(a) Stratosphere (b) Troposphere
greenhouse gases are methane, nitrous oxide, water
(c) Hydrosphere (d) Mesosphere
vapours, CFCs and ozone.
Ans. (d)
Example-8
Sol. The lowest region of atmosphere in which the human
beings along with other organisms live is called What is smog? How is classical smog different from
Troposphere photochemical smog?
Example-4 Sol. The word smog is a combination of smoke and fog. It is a
Which of the following are major particulate pollutants? type of air pollution that occurs in many cities throughout
I Dust II. Mist the world. Classical smog occurs in cool humid climate. It
III. Smoke IV. Smog is also called as reducing smog. Whereas photochemical
smog occurs in warm and dry sunny climate. It has high
(a) I and IV (b) II and IV
concentration of oxidising agents and therefore, it is also
(c) I ,II,III and IV (d) I, II and III
called as oxidising smog.
ENVIRONMENTAL CHEMISTRY 89

Example-9 Ans. (c)

What do you mean by ozone hole? What are its Sol. Classical smog occurs in cold humid climate. It is a mixture
of smoke fog and SO2 Chemically it is a reducing mixture
consequences?
and so it is also called as reducing smog. Photochemical
Sol. Depletion of ozone layer creates some sort of holes in the smog occurs in warm dry and sunny climate the main
blanket of ozone which surround us, this is known as components of the photochemical smog result from the
ozone hole. action of sunlight on unsaturated, hydrocarbons and
1. With the depletion of the ozone layer, UV radiation nitrogen oxides produced by automobile and factories.
filters into the troposphere which leads to aging of Example-14
skin, cataract, sunburn, skin cancer etc. Catalyst converters are fitted automobiles to reduce
2. By killing many of the phytoplanktons, it can damage emission of harmful gases. Catalytic converters change
the fish productivity. unburnt hydrocarbons into
3. Evaporation rate increases through the surface and (a) carbon dioxide and water
stomata of leaves which can decrease the moisture (b) carbon monoxide
content of the soil. (c) methane
Example-10 (d) carbon dioxide and methane

What would have happened if the greenhouse gases were Ans. (a)
totally missing in the earth’s atmosphere? Discuss. Sol. Catalytic converters are fitted into automobiles to reduce
emission of harmful gases. Catalytic converts change
Sol. The solar energy radiated back from the earth surface is
unburnt hydrocarbons into CO2 and H2O.
absorbed by the green house gases (CO2, CH4, O3, CFCs)
Example-15
are present near the earth’s surface.
When rain is accompanied by a thunderstorm, the
They heat up the atmosphere near the earth’s surface and
collected rain water will have a pH value
keep it warm. As a result of these, there is growth of
(a) slightly lower than that of rain water without
vegetation which supports the life. In the absence of this
thunderstorm
effect, there will be no life of both plant and animal on the
(b) slightly higher than that when the thunderstorm is not
surface of the earth.
there
Example-11
(c) uninfluenced by occurrence of thunderstorm
What is chlorosis? (d) Which depends on the amount of dust in air
Sol. Slowdown of process of formation of chlorophyll in plants Ans. (a)
with the presence of SO2 is called chlorosis. Sol. Thunderstorm creates high temperature condition. At this
Example-12 temperature O2 and N2 react to each other and form oxides
Which zone is known as ozonosphere? of nitrogen. Now, oxides of nitrogen react with rain water
and form HNO3. So that collected rain in this condition is
Sol. Stratosphere
slightly acidic.
Example-13
Example-16
…A…smog occurs in warm dry and sunny climate while
What do you mean by Biochemical Oxygen Demand
… B… smog occurs in cool humid climate. Here, A and B
(BOD)?
refer to
Sol. The amount of oxygen required by bacteria to breakdown
(a) ) A  Classical smog, B  Photochemical smog the organic matter present in a certain volume of a sample
(b) A  Normal smog, B  Photochemical smog of water is called Biochemical Oxygen Demand (BOD).
(c) A  Photochemical smog, B  Classical smog
(d) A  Photochemical smog, B  Normal smog
90 ENVIRONMENTAL CHEMISTRY

Example-17 dissolved oxygen in water. When the level of dissolved

The value of BOD of clean water is : oxygen falls below 6 ppm the fish cannot survive.

(a) < 5 ppm Example-21

(b) > more than 5 ppm Which of the following pesticides is introduced during
(c) 1 ppm World War II to control malaria :
(d) 5 ppm (a) Nicotine
Ans. (a) (b) DDT
Sol. Clean water would have BOD value of less than 5 ppm. (c) Aldrin
Example-18 (d) Dieldrin

Pollution from domestic sewage and animal excreta when Ans. (b)

dissolved in river water then it. Sol. During World War II DDT was found to be of great use in
the control of malaria and other insect-borne diseases.
(a) increases BOD of water
Example-22
(b) decreases BOD of water
(c) does not affect BOD of water Soil is polluted by

(d) increases DO of water I. Pesticied

Ans. (a) II. Synthetic fertilizers
Sol. Pollution from domestic sewage and animal excreta when III. Green manure
dissolved in river water then it increases biochemical (a) I and II
oxygen demand of H2O (b) I and II
Example-19 (c) II and III
What are pesticides and herbicides? Explain giving (d) I, II and
examples. Ans. (b)
Sol. Pesticides are the chemical compounds used in agriculture Sol. Pesticides and synthetic fertilizers pollute the soil.
to control the damages caused by insects, rodents, weeds Example-23
and various crop diseases. Waste management
Example: Aldrin, Dilldrin, B.H.C. etc. (a) The proper disposal of wastes
Herbicides: These are the chemicals used to control weeds. (b) The improper disposal of wastes
Example: Triazines (c) Both (a) and (b)
Example-20 (d) The oxidation of wastes in open air
A large number of fish are suddenly found floating dead Ans. (a)
on a lake. There is no evidence of toxic dumping but you Sol. Waste management includes the proper disposal of
find an abundance of phytoplankton. Suggest a reason wastes.
for the fish kill.
Sol. Excessive phytoplankton (organic pollutants such as
leaves, grass trash etc.) present in water are biodegradable.
Bacteria decomposes these organic matters in water.
During this process when large number of bacteria
decomposes these organic matters, they consume the
ENVIRONMENTAL CHEMISTRY 91

Example-24 Example-25
Why the management wastes is of utmost importance? Which of the following chemical has more toxic effect when
(a) The improper disposal of wastes is one of the major used for the purpose dry cleaning of clothes?
causes of environmental degradation (a) Tetrachloroethene (b) H2O2
(b) The poor management causes health problems leading (c) Liquified CO2 (d) None of the above
to epidemic Ans. (a)
(c) Both (a) and (b) Sol. Tetra chloroethene has more toxic effect when used for
(d) It is directly linked with our economy the purpose of dry cleaning of clothes.
Ans. (c)
Sol. As a normal practice, all domestic wastes should be
properly collected and disposed. The poor management
of wastes causes heath problems.
92 ENVIRONMENTAL CHEMISTRY

EXERCISE-1: Basic Objective Questions

Environmental Pollution 8. Non-biodegradable pollutants are created by
(a) Natural disasters
1. Which of the following interrelation with our
(b) Humans
surroundings are included in environmental studies?
(c) Excessive use of resources
(a) Physical and chemical only
(d) Nature
(b) Chemical and economical only
9. Match the Column I with Column II and choose the
(c) Chemical and social
correct option from the codes given below:
(d) All of the above
2. Environmental chemistry deals with the study of the Column I Column II
(a) origin of chemical species in environment A. Biodegradable 1. Nuclear wastes
(b) effect of chemical species in environment pollutant(s) 2. Plastic
(c) Reactions of chemical species in environment B. Non-Biodegradable 3. Discarded
(d) All of the above pollutant(s) vegetables
3. A substance which cause pollution is known as 4. DDT
(a) Catalyst (b) Pollutant Codes:
(c) activator (d) Inhibitor A B
4. Pollutant can be found in the form of : (a) 1.2 3,4
I. Solid (b) 1,2,3 4
II. Liquid (c) 3 1,2,4
III. Gas (d) 1,2,4 3
The correct option(s) is/are
(a) I and II (b) II and III Atmosphere Pollution
(c) I, II and III (d) I and III
5. An average human being requires nearby…A… times 10. There are concentric layers of air regions around earth
more air than the food. and each layer has….A. Here, A refers to
Here, A refers to (a) Same density
(a) 2-4 (b) 200-400 (b) Different density
(c) 12-15 (d) None of these (c) Sometime (a) and sometimes(b)
6. Pollutants which are slowly degradable and remain in (d) None of the above
the environment in an unchanged for many decades, 11. The troposphere extends up to the height of A Km from
termed as : the sea level. Here A refers to.
(a) Biodegradable pollutants (a) ∼ 10 km (b) ∼ 50 km
(b) Non-Biodegradable pollutants (c) ∼ 100 km (d) ∼ 1 km
(c) Both (a) and (b) 12. Stratosphere lies above sea level between :
(d) None of the above (a) 10 -50 km (b) 0-10 km
7. Which of the following are the examples of non-bio- (c) 50-100 km (d) None of the these
degradable pollutants? 13. Which of the following atmosphere layer contains
I. DDT clouds, water vapour and air?
II. Nuclear waste (a) Stratosphere (b) Troposphere
III. Plastic materials (c) Mesosphere (d) All of the these
Select the correct options 14. Ozone layer is present in:
(a) I and II I. Mesosphere II. Hydrosphere
(b) II and III III. Mesosphere IV. Stratosphere
(c) I, II and III (a) I and II (b) II and III
(d) I and III (c) Only IV (d) I, II and II
ENVIRONMENTAL CHEMISTRY 93

15. Ozone layer absorbs mainly …A… Here, A refer to. 25. What is true about CO gas?
(a) UV-radiation (b) X-rays (a) It binds to hemoglobin to form stable compound
(c) IR-radiation (d) All of these (b) It is carcinogenic in nature
16. Which of the following are major gaseous pollutants (c) Both (a) and (b)
present in the troposphere? (d) It includes the chance of heat attack
I. H2S 26. In blood, when concentration of carboxyhaemoglobin
II. Oxides of sulphur, nitrogen and carbon reaches about 3-4%, the oxygen carrying capacity of
III. O3 blood …A… Here, A refers to
(a) I and II (b) I, II, III (a) Increased
(c) III (d) II, III (b) Reduced
17. SO2 gas is poisonous to: (c) Remains same
(a) Animals (b) Plants (d) Sometimes (a) and sometimes (b)
(c) Both (a) and (b) (d) neither (a) nor (b) 27. In pregnant women who have the habit of smoking the
18. Which of the following diseases is caused due to SO2?. increased CO level in blood may induce harmful effects
I. Digestive diseases II. Asthma like :
III. Bronchitis IV. Emphysema (a) Premature birth
(a) I and II (b) II, III and IV (b) Spontaneous abortions
(c) III and IV (d) I, II and III (c) Deformed babies
19. Which of the following pollutant(s)catalyse(s) the (d) All of these
oxidation of sulphur dioxide to sulphur trioxide? 28. Content of CO2 present in atmosphere is :
(a) Particular matter (b) CO2 (a) 3.4% (b) 0.00034%
(c) NO2 (d) All of the above (c) 0.034% (d) 0.34%
20. In an automobile engine, (at high temperature) when 29. Green plants require CO2 for
fossil fuel is burnt, N2 and O2 combine to yield : (a) Respiration (b) Photosynthesis
(a) NO (b) NO2 (c) Excertion (d) All of these
(c) Both (a) and (b) (d) HNO3 30. Which of the following gases cause global warming ?
21. The irritation red haze in the traffic and congested place I. CO2
is due to…A.. II. O3
(a) Oxides of Sulphur (b) Oxides of nitrogen III. CO
(c) CO2 (d) CO IV. Chlorofluorocarbons
22. Which of the following are the harmful effect of (a)I, II and III (b) II, III and IV
nitrogen oxide? (c) I, II and IV (d) I, II, III and IV
I. It retards the rate of photosynthesis 31. In cold places flowers, vegetables and fruits are grown
II. It causes respiratory disease in children in glass covered areas called …A…here A refers to :
III. It is toxic to living tissues. (a) Cold storage (b) Green house
(a) I and II (b) II and III (c) Green glass (d) Both (a) and (c)
(c) I, II and III (d) I and III 32. Atmospheric gases trap the sun’s heat near the earth’s
23. Which of the following statement(s) is//are true about surface and keep it warm. This is called …A… Here A
carbon monoxide? refers to
(a) It is a colourless gas (a) Natural greenhouse effect
(b) It is an odorless gas (b) Tyndall effect
(c) It is highly poisonous (c) Heating effect
(d) All of these (d) All of these
24. Carbon monoxide is mainly released into air by : 33. Which of the following is/are the greenhouse gases?
(a) Automobile exhaust (a) CO2
(b) Incomplete combustion of coal (b) Chloroflurocarbon
(c) Incomplete combustion of firewood (c) CH4
(d) All of the above (d) All of these
94 ENVIRONMENTAL CHEMISTRY

34. Which of the following greenhouse gas is released in 43. Which of the following air pollutants is deposited as
paddy field? dry-deposition ?
I. CFCs (a) SO2 (b) Aerosel
II. CH4 (c) CO (d) All of these
III. SO2 44. Acid rain is harmful for:
(a) Only I (b) Only II I. Agriculture
(c) Only III (d) I and II II. Aquatic ecosystem
35. Which of the following green gas is damaging the III. Buildings and other structures made of stone or
ozone layer? metal.
(a) CFCs (b) CO2 Select the correct option;
(c) CH4 (d) SO2 (a) I and II only
36. Excess use of chemical fertilizers increases the quantity (b) II and III only
of…A… (air pollutant) in the atmosphere. Here, A (c) I, II and III
refers to.. (d) I and III only
(a) Nitrogen oxides 45. The Taj Mahal in India is affected by pollutant:
(b) Carbon dioxide (a) SO2 (b) O3
(c) Carbon monoxides (c) CFC (d) None of these
(d) Methane 46. Which of the following is responsible for damaging
37. pH of normal rain water is : Tajmahal and other monuments near Agra ?
(a) 3 (b) 7 (a) SO2
(c) 5.5 (d) 10 (b) NO2
38. Rain water is slightly acidic because (c) Industrial Pollutants
I. Water reacts with CO2 and forms H2CO3 (d) All of these
II. Rain water reacts with CO and forms H2CO3 47. What do you mean by Taj-Trapezium?
Identify the correct option: (a) A Trapezium shaped park inside the Tajmahal
(a) Both I and II are correct (b) A Trapezium shaped residential colony developed
(b) I is correct and II is incorrect near Tajmahal for promoting greenary
(c) I is incorrect and II is correct (c) A Plan that aims at cleaning the air in an area that
(d) Both I and II are in correct includes the towns of Agra, Firozabed, Mathura
39. When the pH of the rain water drops below 5., it is and Bharatpur
called …A…A, Here, A refers to : (d) Both (a) and (b)
(a) Acid rain (b) Base rain 48. The viable particulate stand for :
(c) Neutral rain (d) Normal rain I. Minute living organisms present in atmosphere
40. Acid rain is due to : II. Minute non-living particles present in atmosphere
I. Oxides of nitrogen (a) Inly I (b) Only II
II. Oxides of sulphur (c) Both I and II (d) Neither I or II
III. Methane present in the air 49. Which of the following is not a viable particulates :
(a) I and II (b) II and III (a) Bacteria (b) Fungi
(c) I, II and III (d) I and III (c) Moulds (d) Mist
41. How can we reduce the rate of global warming? 50. Non-viable particulates are classified on the basis of :
(a) By minimizing use of automobiles (a) Nature of particle (b) Size of particle
(b) By avoiding burning of dry leaves (c) Both (a) and (b) (d) Neither (a) nor (b)
(c) Both (a) and (b) 51. Mist is produced by :
(d) None of the above I. Particles of spray liquids
42. Aerosol particles of oxides are ammonium salts in rain II. Condensation of vapour in air
drops results in …A… here A refer to. (a) Only I (b) Only II
(a) Dry-deposition (b) Wet deposition (c) Both I and II (d) Neither I nor II
(c) Both (a) and (b) (d) Normal deposition
ENVIRONMENTAL CHEMISTRY 95

52. Herbicides and insecticides are travel through air and 61. Which of the following is/are common components of
form …A… Here A refers to: photochemical smog?
(a) Smoke (b) Dust (a) O3 (b) Acrolein
(c) Mist (d) All of these (c) PAN (d) All of these
53. The effect of particulate pollutants are largely 62. Which of the following components of photochemical
dependent on the …A… Here, A refers to. smog act as powerful eye irritiants?
(a) Particle size I. O3
(b) Particles nature II. PAN
(c) Neither (a) nor (b) III. Hydrocarbon
(d) Particle configuration (a) I, II and III (b) I and II
54. Which of the following is the major particulate matter (c) I and II (d) II and III
immitted by vehicles. 63. Which of the following is/are the primary precursor(s)
(a) Hg (b) Pb of the photochemical smog?
(c) Cd (d) Co (a) PAN (b) NO2
55. The word smog stands for : (c) Hydrocarbon (d) Both (a) and (c)
(a) Smoke 64. Catalytic converts are used to control…A… Here, A
(b) Fog refers to.
(c) Combination of Smoke and fog (a) Photochemical smog (b) Classical smog
(d) Neither (a) nor (b) (c) water pollution (d) Acid rain
56. Classical smog is a mixture of 65. Point out the plants which are most effective for
(a) smoke + SO2 (b) Smoke + H2O controlling of photochemical smog ?
(c) Smoke+fog+H2O (d) Smoke+fog+SO2 (a) Pinus (b) Juniparus
57. Classical smog is also called …A…smog. Here A (c) Vitis (d) All of these
refers to 66. Which of the following protect us from the harmful
(a) Oxidising (b) Reducing UV-radiation coming from the sun?
(c) Both (a) and (b) (d) Foam I. O2 II. O3
58. Photochemical smog has …I… concentration of III. N2 IV. CO2
oxidising agents and is therefore, called as …II… (a) I and II (b) II and IV
smog. Here, I and II refer to : (c) II only (d) I and IV
(a) I  low, II  reducing 67. The disease caused by UV radiation(s) in human is/are:
(b) I  high, II  reducing I. Melanoma (skin cancer) II. Heart attack
(c) I  high, II  oxidising III. Hypertension IV. Cough cold
(d) I  low, II  oxidising (a) Only I (b) II, III and IV
59. Which of the following options represents the PAN? (c) III and IV (d) I, III and IV
(a) CH2O (b) CH2=CH-CHO 68. Which of the following reaction(s) is/are happen during
the formation of O3 layer in stratosphere ?
(c) CH3CH2-O-N=O (d) (a) O2 (g) UV
O(g)+O(g)
(b) O(g)+O 2 (g) 
UV
(g)O3 (g)
60. Which of the following are involved in the formation of
(c) O3 (g) 
UV
O2(g)+O(g)
PAN?
I. NO2 (d) All of the above.
II. O3 69. Thermodynamically ozone is :
III. Unburnt hydrocarbon (a) Stable
IV. CO2 (b) Unstable
(a) I and II only (b) I, II and IV (c) Sometimes stable and sometimes unstable
(c) I, III and IV (d) I, II and III (d) None of the above
96 ENVIRONMENTAL CHEMISTRY

70. How do CFCs cause thinking of ozone layer in 79. In summer season, nitrogen dioxide and methane reacts
stratosphere ? with …A… and …B… atoms forming chlorine sinks.
(a) CFCs are transporting agents for continuously Here, A and B refer to
generating chlorine radicals into stratosphere (a) A  Chlorine, B  Carbon dioxide
(b) CFCs are transporting agents for continuously (b) A  Chlorine monoxide, B  Chlorine
generating fluorine radicals into stratosphere (c) A  Chlorine, B  Chlorine monoxide
(c) Both (a) and (b) (d) A  ozone, B  Chlorine
(d) In presence of UV CFC formed stable compound 80. Polar stratospheric cloud is formed over Antarctica
which degrade the ozone layer during ..A.. Here, A refers to
71. The main reason of ozone layer depletion is : (a) Summer season (b) Winter season
I. release of CFCs (c) Both (a) and (b) (d) None of the above
II. release of CO2 81. Which of the following is/are the harmful effect(s) of
III. release of CH4 UV radiation?
(a) Only I (b) Only II I. It causes mutation in the cell
(c) Only III (d) I, II and III II. UV radiation leads to ageing of skin
72. CFCs also knows as: III. It kills many phytoplankton
(a) Pyrenes (b) Freons IV. It causes global warming
(c) Radons (d) Both (a) and (b) (a) I and II are correct. III and IV are incorrect
73. CFCs are used in refrigerators, air conditioners because: (b) I, II and III are correct, IV is incorrect
(a) Non-reactive in nature (c) I, II, III and IV are correct
(b) Non-toxic in nature (d) II and IV are correct
(c) Non-flammable in nature 82. Match the Column I with Column II and choose the
(d) All of these. correct option from the codes given below :
74. CFCs deplete the ozone layer because Column I Column II
(a) They release Cl2 gas A. Gaseous air pollutants 1. CO2
(b) They release chlorine free radical B. Particulate pollutants 2. Smoke
(c) They release F2 gas 3. Smog
(d) Both (a) and (b) 4. O3
75. The depletion of ozone layer is known as
Codes
I. ozone hole
A B
II. ozone centre (a) 1,2 3,4
III. ozone point (b) 2,3 1,4
(a) Only I (b) II and III (c) 1,4 2,3
(c) I and II (d) I and III (d) 3,4 1,2
76. The depletion of ozone hole was first reported in …I… 83. Match the Column I with Column II and choose the
over Antarctica. Here I refers to : correct option from the codes given below :
(a) 1920 s (b) 1980 s
Column I Column II
(c) 1940 s (d) 1970 s
A. SO2 1. Binds o haemoglobin
77. Ozone hole is found over :
B. NO2 2. Leads to stiffness of flower Buds
(a) India (b) Africa
C. CO 3. Irritant red haze in the traffic
(c) Antarctica (d) America
78. Chlorine sinks are formed during :
Codes
I. Summer II. Winter
A B C
(a) Only I
(a) 1 2 3
(b) Only II
(b) 3 2 1
(c) Both I and II
(c) 2 3 1
(d) Neither I nor II
(d) 1 3 4
ENVIRONMENTAL CHEMISTRY 97

84. Dinitrogen and dioxygen are main constituents of air 91. The consequence of global warming may be…
but these do not react with each other to form oxides of I. Increase in average temperature of the earth
nitrogen because. II. Melting of Himalayan Glaciers
(a) The reaction is endothermic and requires very high III. Increased biochemical oxygen demand.
temperature IV. Eutrophication
(b) The reaction can be initiated only in presence of a (a) I and III (b) II and IV
catalyst (c) I and II (d) I and IV
(c) Oxides of nitrogen are unstable 92. Which of the following belongs to secondary air
(d) N2 and O2 are unreactive pollutants?
85. Which of the following statement(s) is/are true? (a) PAN (b) Hydrocarbon
I. Carbon monoxide is a secondary air pollutant (c) SO2 (d) CFCs
II. SO2 causes brown air effect during traffic 93. Match the Column I with the Column II and choose the
congestion in cities. correct option from cods given below :
III. DDT is a non-biodegradable pollutant. Column I Column II
(a) I and II (b) II and III A. Normal 1. H2CO3
(c) Only III (d) I, II and III B. Acid rain 2. HNO3
86. Which of the following statement(s) is/are incorrect 3. HCl
regarding photochemical smog ? 4. H2SO4
(a) CO does not play any role in photochemical smog Codes :
formation A B
(b) Photochemical smog is an oxidising agent in (a) 2,4 1,3
character (b) 1,3 2,4
(c) Photochemical smog is formed through (c) 1 1,2,4
Photochemical reaction involving solar energy (d) 1,2,4 1
(d) Photochemical smog does not cause irritation in 94. Match the terms given in Column I with the compounds
eyes and throat given in Column II and choose the correct option from
87. Photochemical smog is caused by light mediated the codes given below.
reaction between: Column I Column II
(a) NO2 and unsaturated hydrocarbons A. Acid rain 1. CHCl2 – CHF2
(b) NO2 and O3 B. Photochemical smog 2. CO
(c) SO2 and unburnt hydrocarbons C. Combination with 3. CO2
(d) SO2 and O3 haemoglobin 4. SO2
88. Which of the following statement is incorrect about D. Depletion of ozone 5. Unsaturated hydrocarbons
particulate pollutant? layer
(a) It is found in O3 layer
Codes
(b) particulate pollutant are present in the troposphere
A B C D
(c) Dust, mist and smog are examples of the
(a) 3,4 5,4 2 1
particulate pollutants
(b) 2 1 3 4
(d) It is harmful for plants and animals
(c) 1 2 3,4 5,4
89. Photochemical smog does not contain:
(d) 5,4 3,4 2 1
(a) O3 (b) Hydrocarbon
95. CO emitted automobiles prevents O-transport to body
(c) NO2 (d) O2
tissues by:
90. Bad ozone is found in the :
(a) Changing O2 to CO2
(a) Mesosphere
(b) Destroying hemoglobin
(b) Troposphere
(c) Forming a stable compound with hemoglobin
(c) Stratosphere
(d) Obstructing the reaction of O2 with haemoglobin
(d) Ionosphere
98 ENVIRONMENTAL CHEMISTRY

96. Match the Column I with the Column II and choose the (d) None of these
correct option from the codes given below. 104. Concentration of dissolve oxygen in clear water is
Column I Column II (a) ∼ 10 ppm (b) ∼ 100 ppm
A. Nuclear power 1. Radioactive wastes (c) ∼ 5 ppm (d) ∼ 1 ppm
plant 2. Release of NO2 105. The amount of oxygen required by bacteria to break
B. Burning of fossil 3. No pollution down the organic matter present in a certain volume of
fuel water is called…A…Here, A refers to
C. Solar energy (a) BOD (b) DO
Codes : (c) COD (d) All of these
A B C 106. BOD measures the amount of
(a) 1 2 3 I. Inorganic material in water
(b) 3 2 1 II. Organic material in water.
(c) 3 1 2 Identify the correct option:
(d) 2 1 3 (a) Only I (b) Only II
97. ‘Good ozone’ is found in the (c) Both I and II (d) neither I nor II
(a) Mesosphere (b) Troposphere 107. The value of BOD of highly polluted water is :
(c) Stratosphere (d) Ionosphere (a) More than 17 PPm (b) More than 5 ppm
(c) 1 ppm (d) 5 ppm
Water Pollution 108. Heavy metal water pollutants are dangerous to human
because:
98. Which of the following is most essential for life? I. Human body cannot excrete them
(a) Water (b) Carbon dioxide II. Human body can excrete them
(c) Nitrogen (d) Carbon monoxide III These metals can damage kidney and liver.
99. …A… of pollution are those where a source of Which of the following is/are the correct option(s)?
pollution cannot be identified. Here, A refers to : (a) I, II and III are correct
(a) Point source (b) Non-point source (b) I and II are correct
(c) Both (a) and (b) (d) Main source (c) II and III are incorrect
100. Which of the following is/are the examples of non-point (d) I and III are correct
sources of pollution? 109. Which of the following pollutants cause water
I. Agricultural run off pollution?
II. Acid rain (a) Oil spills in ocean (b) Pesticides
III. Drainage (from steels, lawns) (c) Detergents (d) All of these
(a) I and II (b) II and III 110. Match the items in Column I and Column II and choose
(c) I,II and III (d) I and III the correct option from the codes given below :
101. Disease causing water pollutants are called: Column I Column II
(a) Chemical pollutants (b) Organic wastes A. UV-radiation 1. Biomagnification
(c) Pathogens (d) Both (a) and (b) B. DDT 2. Skin cancer
102. Human excreta contain bacteria such as Escherichia C. Phosphate 3. Eutrophication
coli and streptococcus faecalis, which cause Codes
(a) Respiratory diseases A B C
(b) Gastrointestinal diseases (a) 1 2 3
(c) Hypertension (b) 3 2 1
(d) All of these (c) 2 3 1
103. Organic water waste are : (d) 2 1 3
(a) Non-biodegradable
(b) Biodegradable
(c) Both (a) and (b)
ENVIRONMENTAL CHEMISTRY 99

111. Match the pollutants given in Column I with their 116. A process in which nutrient enriched water bodies
effects given in Column II and choose the correct support a dense plant pollutation, which kills animal
option from the codes given below. life by depriving it of oxygen is known as …A…Here,
Column I Column II A refers to :
A. Sulphur dioxide in air 1. Global warming (a) Biological oxygen demand
B. Carbon dioxide in air 2. Eutrophication (b) Biomagnification
C. Phosphate fertilisers in 3. Acid rain (c) Eutrophication
H 2O 4. Increases BOD (d) Both (a) and (b)
D. Detergents in water level in water 117. Fluoride deficiency in drinking water causes :
Codes: I. Harmful effect on home
A B C D II. Tooth decay
(a) 3 1 4 2.4 III blue baby syndrome
(b) 3 1 2,4 4 (a) Only I (b) Only II
(c) 1 3 2,4 4 (c) Only III (d) I and II
(d) 2,4 4 1 3 118. The F- ions make the enarnel of teeth :
112. Source(s) of dissolved oxygen in water is/are : (a) Soffer
(a) carbon dioxide and water (b) Harder
(b) carbon monoxide (c) Sometimes (a) and sometimes (b)
(c) methane (d) None of the above
(d) carbon dioxide and methane 119. When fluoride ion concentration in water is more than 2
113. When domestic sewage mixes with river water. ppm then it causes :
(a) Small animals like rats will die after drinking river I. Tooth decay
water II. Brown motting of teeth
(b) the increased microbial activity releases III. Harmful effect to bones
micronutrients such as iron (a) I and II (b) II and III
(c) The increased microbial activity uses up dissolved (c) I, II, and III (d) None of these
oxygen 120. The prescribed upper limit concentration of lead in
(d) the river water is still suitable for drinking as drinking water is :
impurities are only about 0.1% (a) ∼ 50 ppb (b) ∼ 2 ppb
114. Phosphate containing fertilizers cause water pollution. (c) ∼ 200 ppb (d) ∼ 500 ppb
Addition of such compounds in water bodies causes. 121. Excess nitrate in drinking causes :
I. Enhanced growth of algae I. Tooth decay
II. decreases amount of dissolved oxygen in water II. Methemoglobinemia
III. deposition of calcium phosphate III. Digestive disorder
IV increase in fish population (a) Only I (b) Only II
(a) I and III (b) I, II and IV (c) Only III (d) III and IV
(c) I and II (d) III and IV 122. Statement I Excessive growth of algae inhibited the
115. Polychlorinated biphenyl (PCBs) are growth of other organism which lives in water due to it
I. Non-Carcinogenic in nature decreases the DO in water.
II. Carcinogenic in nature Statement II The value of BOD of polluted water is less
III used to cleansing solvent than 5 ppm.
(a) I and II are true (b) II and III are true Identify the correct statement(s).
I I, III and IV are true (d) I and IV are true (a) Only I (b) Only II
(c) Both I and II (d) Neither I nor II
100 ENVIRONMENTAL CHEMISTRY

123. Some statements are given below : 130. Most of the organic toxins are water…A…and …B…
I. If the concentration of dissolve oxygen of water is Here, A and B refer to.
below 6 ppm, the growth of aquatic life gets (a) A  soluble, B  biodegradable
inhibited. (b) A  soluble, B  non-biodegradable
II. Clean water would have BOD value more than 17 (c) A  insoluble, B  non-biodegradable
ppm. (d) A  insoluble, B  biodegradable
Select the correct option:
I II 131. High persistent toxins are transferred from …A…
(a) Correct Incorect trophic level to…B.. trophic level through …C…Here,
(b) Incorrect Correct A B and C refer to..
(c) Correct Correct (a) A  lower, B  higher, C  food series
(d) Incorrect Incorrect (b) A  lower, B  higher, C  food chain
124. BOD in the river water:
(c) A  higher, B  lower, C  food chain
(a) Remains unchanged when algai bloom occurs
(d) A  high, B  lower, C  food series
(b) Has no relationship with concentration of O2 in the
132. Which of the following pesticide(s) cause(s) severe
water
nerve toxicity?
(c) increases when sewage get mixed with river water
(a) DDT (b) Carbamate
(d) gives a measure of salmonella in the water.
(c) Aldrin (d) None of these
125. Nuisance growth of aquatic plants and bloom forming
133. Match the Column I with the Column II and choose the
algae in natural waters is
correct option from the codes given below.
(a) Carbon (b) Sulphur
Column I Column II
(c) Calcium (d) Phosphorus
A. Domestic sewage 1. Micro-organism
126. Assertion (A)If BOD level of water in a pond is more
B. Nuclear power plant 2. Organic waste
than 20 ppm, it is said to highly polluted.
C. Chemical used for 3. Radioactive substance
Reason (R) High BOD means low activity of bacteria in
killing insects and 4. Pesticides
water.
fungi
(a) Both A and R are correct : R is the correct
explanation of A Codes
(b) Both A and R are correct; R is not the correct A B C
(a) 1,2 3 4
explanation of A
(b) 2 1,3 4
(c) A is correct; R is incorrect
(d) R is correct ; A is incorrect (c) 2,3 4 1
(d) 4 2 1,3
134. Which of the following is/are example(s) of herbicides?
Soil Pollution and industrial waste
(a) Sodium chlorite (b) Sodium arsinite
(c) Both (a) and (b) (d) KmnO4
127. Naturally occurring chemical nicotine is obtained from:
(a) Power plants (b) Cotton 135. Industrial solid wastes are :
(a) Biodegradable (b) Non-biodegradable
(c) Paddy (d) Tobacco
(c) Both (a) and (b) (d) None of these
128. Nicotine is used as :
136. Biodegradable industrial wastes are generated by :
I. Fertilizers
(a) Cotton mills (b) Paper mills
II. Pest controlling chemical
III. Medicine (c) Food processing unit (d) All of these
137. Non-biodegradable industrial wastes are generated by :
(a) I and II (b) Only I
(a) Thermal power plants (b) Steel plant
(c) Only II (d) I, II and III
(c) fertilizer industries (d) All of these
129. Pesticides are basically…A… toxic chemical with
ecological repercussions., Here, A refers to
(a) Natural (b) Synthetic
(c) Organic (d) Both (b) and (c)
ENVIRONMENTAL CHEMISTRY 101

138. How to electricity is produced garbage ? Here, A refers to

(a) Garbage is burnt open air (a) Green fuel (b) Biofuel
(b) Garbage is cultured with bacteria and produce (c) Octane fuel (d) Toxic fuel
methane
(c) Both (a) and (b) Green Chemistry
(d) The oxidation wastes in open air
139. Methane is commonly known as 144. Green chemistry involves :
(a) Biogas (b) Laughing gas (a) Minimum pollution of deterioration to the
(c) producer gas (d) LPG environment
140. Which of the following statement(s) is/are correct (b) To excess exploitation of natural resources
regarding to waste management? (c) Environment unfriendly and cost-ineffective
I. Wastes are separated into biodegradable and non- producer
biodegradable wastes (d) To study the reactions in plants
II. Non-biodegradable wastes such as plastic glass 145. Why water is better aqueous medium for most of the
etc., are sent for recycling. synthetic chemical reaction?
III. Biodegradable wastes are deposited in landfills and I. Use of water is cost effective
are converted into compost. II. It is devoid of any carcinogenic effects
(a) I and II (b) II and III (a) I and II (b) II and III
(c) I, II and III (d) I and III (c) I. II and III (d) I and III
141. A farmer was using pesticides on his farm. He used the 146. “Reducing potentially hazardous waste through smarter
production of his farm as food for rearing fishes. After production.”
examining the fishes, scientist told that fishes were not This represents a great step forward for
fit for human consumption because (a) Green revolution (b) green chemistry
(a) fishes were highly resistant to disease (c) Industrial revolution (d) Green biotechnology
(b) fishes were killed by pesticides 147. Which type of harm in environment will be prevented
(c) large amount of pesticides had accumulated in the by stopping use of tetra-chloroethene?
tissues of fishes. (a) At contaminates the ground water
(d) Both (a) and (b) (b) It is also a suspected carcinogen
142. Match the pollutant(s) in Column I with the effect(s) in (c) Both (a) and (b)
Column II and choose the correct option from the codes (d) None of the above
given below. 148. Match the Column I and Column II and choose the
correct option from the codes given below :
Column I Column II Column I Column II
A. Oxides of sulphur 1. Global warming A. Dry cleaner which is 1. Production of CH3CHO
B. Nitrogen dioxide 2. Damage to kidney environment by environment
C. Carbon dioxide 3.‘Blue baby’ syndrome unfriendly friendly process
D. Nitrate in drinking 4. Respiratory diseases B. Dry cleaner which is 2. Tetrachloroethene
water 5.Red haze in traffic and environmental friendly
E. Lead congested areas C. Ionic catalysts in 3. H2O2
Codes aqueous medium
A B C D E Codes:
(a) 1 2 3 4 5 A B C
(b) 4 5 1 2 3 (a) 1 2 3
(c) 5 4 1 2 3 (b) 3 2 1
(d) 4 5 2 3 1 (c) 2 3 1
143. Fuel obtained from plastic waste has high octane rating. (d) 1 3 2
It contains no lead and is known as …A….
102 ENVIRONMENTAL CHEMISTRY

149. Match the Column I with the Column II and choose the
correct option from the codes given below.
Column I Maximum concentration
(Metals) (ppm or Mg dm-3)
A. Fe 1. 0.005
B. Cd 2. 0.2
C. Mn 3. 5.0
D. Zn 4. 0.05

Codes
A B C D
(a) 1 3 2 4
(b) 2 1 4 3
(c) 2 1 3 4
(d) 1 2 4 3
150. If there were no green house gases in the atmosphere,
then the temperature of the earth
(a) increases (b) decreases
(c) remain same (d) cannot predicted
ENVIRONMENTAL CHEMISTRY 103

EXERCISE-2: Previous Years Questions

1. Phosphate pollution is brought about by (AIPMT 1997) (a) PAN (b) PBN
(a) phosphate rocks (c) NO2 (d) All of these
(b) fertilizers 9. Use of chlorofluorocarbon is not encouraged because
(c) phosphate rocks and sewage (KCET 2005)
(d) fertilizers and sewage (a) they are harmful to the eyes of people
2. Greenhouse effect is caused by: (b) they damage the refrigerators and air conditioners
(AIPMT 2002, AFMC 2002) (c) they eat away the ozone in the atmosphere
(a) Green plants (b) Infrared rays (d) they destroy the oxygen layer
(c) UV rays (d) X-rays 10. The water pollutants mainly responsible for
3. When rain is accompanied by a thunderstorm, the eutrophication are (Punjab PMET 2006)
collected rain water will have a pH value (a) Cd, Pb and Hg present in industrial waste
(AIEEE 2003) (b) heavy metals present in mining waste
(a) slightly lower than that of rain water without (c) detergents and fertilisers containing phosphate anion
thunderstorm (d) polychlorinated biphenyls
(b) slightly higher than that when the thunderstorm is 11. Match the column I and column II and pick the correct
not there matching from the codes given below.
(c) uninfluenced by occurrence of thunderstorm (Kerala CEE 2006)
(d) which depends on the amount of dust in air Column I Column II
4. Biological Oxygen Demand (BOD) is a measure of A. Peroxyacetyl nitrate 1. Waste incineration
(AIIMS 2003) B. Polycylic aromatic 2. Global warming
(a) amount of oxygen needed by green plants during C. Dioxins 3. Photochemical smog
night D. Indigo 4. Carcinogens
(b) amount of carbon monoxide inseparably combined E. IR active molecules 5. Vat dye
with haemoglobin Codes
(c) industrial wastes poured into water bodies A B C D E
(d) extent to which water is polluted with organic (a) 3 4 1 5 2
compounds (b) 1 2 3 4 5
5. Which one of the following is responsible for depletion (c) 3 5 1 2 4
of the ozone layer in the upper strata of the atmosphere? (d) 5 3 1 2 4
(AIPMT 2004) 12. Which of the following is secondary pollutant?
(a) Polyhalogens (b) Ferrocene (Manipal 2007)
(c) Fullerenes (d) Freons (a) CO2 (b) N2O
6. Nitrogen oxides produced from the presence of (c) PAN (d) SO2
(KET 2004) 13. The brown haze of photochemical smog is largely
(a) O2 and O3 attributable to (Punjab PMET 2007)
(b) O2 and N2 (a) NO
(c) oxides of sulphur and nitrogen (b) NO2
(d) O3 and N2 CH3 – COONO2
7. The smog is essentially caused by the presence of : ||
(c) O
(Guj. CET 2004)
(d) CH2 = CHCH = O
(a) O2 and O3
(b) O2 and N2
14. Which one of the following compounds helps in
(c) Oxides of sulphur and nitrogen
achieving equilibrium between O2 and CO2 in
(d) O3 and N2
atmosphere? (EAMCET 2008)
8. The basic components of the smog are (AMU 2005)
104 ENVIRONMENTAL CHEMISTRY

(a) Chlorophyll (b) Vitamin-B12 22. DDT residues are rapidly passed through food chain
(c) Porphyrin (d) Acetyl salicylic acid causing biomagnification because DDT is
15. Green chemistry means such reactions which : (AIPMT 2009)
(AIPMT 2008) (a) Non-toxic to aquatic animals
(a) produce colour during reactions (b) Water soluble
(b) reduce the use and production of hazardous (c) Non-Biodegradable
chemicals (d) Moderately toxic
(c) are related to the depletion of O3 layer 23. The chemical entities present in thermosphere of the
(d) study the reactions in plants. atmosphere (EAMCET 2009)
+ + +
16. Freon gas causing stratospheric ozone depletion is (a)O2 , O , NO (b) O3
mainly released from : (WB CET 2008) (c) N2, O2, CO2, H2O (d) O3, O2+, O2
(a) Refrigerator (b) Automobile 24. Pollution is (MHT CET 2010)
(c) Thermal power plant (d) Steel industry (a) removal of top soil
17. The process of ‘eutrophication’ is due to the (b) release of toxic and undesirable materials in
(Kerala CEE 2008) environment
(a) increase in concentration of insecticide in water (c) conservation of energy
(b) increase in concentration of fluoride ion in water (d) All of the above.
(c) reduction in concentration of the dissolved oxygen 25. UV radiations brings about (RPMT 2010)
in water due to phosphate pollution in water (a) skin cancer (b) mouth cancer
(d) attack of younger leaves of a plant by peroxyacetyl (c) lung cancer (d) liver cancer
nitrate 26. Gas released during Bhopal Gas Tragedy was
18. 5L aqueous solution is kept in the presence of oxygen (RPMT 2010)
and suitable microorganism for five days at 20°C. If the (a) methyl isocyanate (b) potassium isocyanate
O2 consumed is 0.2g, the BOD value of the sample is (c) sodium isocyanate (d) ethyl isothiocyanate
(EAMCET 2008) 27. Global warming can be controlled by :
(a) 4 ppm (b) 0.4 mg L–1 (CBSE-AIPMT 2010)
(c) 40 ppm (d) 20 mg L–1 (a) Reducing deforestation, cutting down use of fossil
19. Assertion (A): London smog is oxidising in nature. fuel.
Reason (R): London smog contains O3, NO2 and (b) Reducing reforestation, increasing the use of fossil
hydrocarbons. (AIIMS2009) fuel
(a) Both A and R are correct and R is the correct (c) Increasing deforestation, slowly down the growth
explanation of A. of human population
(b) Both A and R are correct but R is not the correct (d) Increasing deforestation, reducing efficiency of
explanation of A energy usage
(c) A is correct but R is incorrect 28. Greenhouse effect is caused by (JCECE2010)
(d) Both A and R are incorrect (a) NO2 (b) CO
20. Photochemical smog is caused due to the presence of (c) NO (d) CO2
(Kerala CEE2009) 29. Identify the incorrect statement from the following.
(a) oxides of sulphur (b) oxides of nitrogen (AMU 2010)
(c) oxides of carbon (d) lead (a) Oxides of nitrogen in the atmosphere can cause the
21. Antidote for carbon monoxide is/are depleting of ozone layer.
(CG PMT, Haryana PMT 2009) (b) Ozone absorbs the intense ultraviolet radiations of
(a) carborundum the sun
(b) dry ice (c) Depletion of ozone layer is because of its chemical
(c) carbonic acid reactions with chlorofluoro alkanes.
(d) pure oxygen and carbogen (d) Ozone absorbs infrared radiations.
ENVIRONMENTAL CHEMISTRY 105

30. ‘Good ozone’ is found in the (AIPMT Mains 2011) (a) Both A and R are correct and the R is the correct
(a) Mesosphere (b) Troposphere explanation of the A
(c) Stratosphere (d) Ionosphere (b) Both A and R are correct but the R is not the
31. Which of the following statements is not true ? correct explanation of the A
(AIPMT 2011) (c) A is correct but R is incorrect.
(a) Concentration of DO below 6 ppm is good for the (d) Both A and R is incorrect.
growth of fish 38. Which one of the following statements is not true?
(b) Clean water would have a BOD value of less than 5 (Karnataka NEET 2013)
ppm (a) Clean water would have a BOD value of 5 ppm.
(c) Oxides of sulphur, nitrogen and carbon are the (b) Fluoride deficiency in drinking water is harmful.
most widespread air pollutants Soluble fluoride is often used to bring its
(d) pH of drinking water should be between 5.5-9.5 concentration upto 1 ppm.
32. Excess nitrate in drinking water can cause (c) When the pH of rain water is higher than 6.5, it is
(Kerala CEE 2011) called acid rain.
(a) methemoglobinemia (b) kidney damage (d) Dissolved Oxygen (DO) is cold water can reach a
(c) liver damage (d) laxative effect concentration upto 10 ppm.
(e) leucoderma 39. Assertion (A): Nitrogen oxides are one of the
33. Eutrophication is due to (AMU 2011) components of photochemical smog.
(a) SO24 ion present in water Reason (R): Vehicular pollution is a major source of
nitrogen oxides (AIIMS 2013)
(b) NaCl present in water
(a) Both A and R are correct and R is the correct
(c) PO34 present in water explanation A
(d) heavy metal present in water (b) Both A and R are correct but R is not the correct
34. Photochemical smog is caused by light mediated explanation of A
reaction between : (AIPMT 2012) (c) A is correct but R is incorrect
(a) NO2 and unsaturated hydrocarbons (d) A is correct but R is incorrect
(b) NO2 and O3 40. Which one of the following is not a common
(c) SO2 and unburnt hydrocarbons component of photochemical smog?
(d) SO2 and O3 (CBSE AIPMT 2014)
35. Which one of the following statements regarding (a) Ozone (b) Acrolein
photochemical smog is not correct? (c) Peroxyacetyl nitrate (d) Chlorofluorocarbons
(CBSE, AIPMT 2012) 41. Among the following, the one which is not a
(a) Carbon monoxide does not play any role in ‘greenhouse gas’, is (Kerala CEE 2014)
formation of photochemical smog. (a) N2O (b) CO2
(b) Photochemical smog is an oxidising agent by (c) CH4 (d) O2
character. 42. Assertion: (A) London smog is produced when carbon
(c) Photochemical smog is formed through soot particles combine with gaseous oxides of sulphur.
photochemical reaction involving solar energy. Reason: Presence of carbon particles and SO2 makes it
(d) Photochemical smog does not cause irritation in reducing in nature. (AIIMS 2017)
eyes and throat. (a) Both A and R are correct and R is the correct
36. BOD stands for (AMU 2012) explanation of A
(a) Biochemical oxygen demand (b) Both A and R are correct but R is not the correct
(b) Biochemical oxygen degradation explanation of A
(c) Bacterial oxygen demand (c) A is correct but R is incorrect
(d) Neither I nor II (d) Both A and R are incorrect
37. Assertion (A): CO and NO combine with haemoglobin.
Reason (R): Both have equal affinity for haemoglobin.
(AIIMS 2012)
106 ENVIRONMENTAL CHEMISTRY

43. Which of the following is a sink for CO? (NEET 2017) 49. The incorrect statement about carbon monoxide is
(a) Microorganisms present in the soil (NEET 2020)
(b) Oceans (a) It reduces the oxygen – carrying ability of blood.
(c) Plants (b) The carboxyhaemoglobin (haemoglobin bound to
(d) Haemoglobin CO) is less stable than oxyhaemoglobin.
44. Which of the following chemicals are used to (c) It is produced due to incomplete combustion
manufacture methyl isocyanate that caused “Bhopal (d) It forms carboxyhaemoglobin.
tragedy”? (JIPMER 2018) 50. Match list-I with list-II (NEET 2021)
(i) Methylamine (iii) Phosgene List – I List – II
(iii) Phosphine (iv) Dimethylamine (a) (i) Acid rain
(a) (i) and (ii) (b) (iii) and (iv) 2SO2  g   O2  g   2SO3  g 
(c) (i) and (iii) (d) (ii) and (iv)
(b) (ii) Smog
45. Which oxide of nitrogen is not a common pollutant
 
introduced into the atmosphere both due to natural and HOCl  g  
hv
 O H  Cl
human activity? (NEET 2018)
(c) (iii) Ozone
(a) N2O (b) NO2
(c) N2O5 (d) NO CaCO3  H 2SO 4  depletion
46. Among the following, the one that is not a greenhouse CaSO 4  H 2 O  CO 2
gas is (NEET 2019) (d) (iv) Tropospheric
(a) methane (b) ozone NO2  g  hv pollution
(c) sulphur dioxide (d) nitrous oxide
NO  g   O  g 
47. Assertion: Photochemical smog results from the action
of sunlight on NOx and hydrocarbons. Choose the correct answer from the options given
Reason: It occurs in warm, dry and sunny climate. below.
(AIIMS 2019) (a) (a)-(iv), (b)-(iii), (c)-(i), (d)-(ii)
(a) If both assertion and reason are true and reason is (b) (a)-(iii), (b)-(ii), (c)-(iv), (d)-(i)
the correct explanation of assertion (c) (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)
(b) If both assertion and reason are true but reason is (d) (a)-(ii), (b)-(iii), (c)-(iv), (d)-(i)
not the correct explanation of assertion
(c) If assertion is true but reason is false
(d) If both assertion and reason are false
48. Which of the following statement is NOT true about
acid rain? (NEET 2020)
(a) It is due to reaction of SO2, NO2 and CO2 with rain
water
(b) Causes no damage to monuments like Taj Mahal
(c) It is harmful to plants
(d) Its pH is less than 5.6
ENVIRONMENTAL CHEMISTRY 107

EXERCISE-3: Achiever’ s Section

Single Choice Questions
1. Presence of which fuel gas in the exhaust fumes shows 11. The statement which is not true
incomplete combustion of fuel (a) NO2 does not play any role in photochemical smog
(a) Sulphur dioxide (b) SO3 is more harmful air pollutant than SO2
(b) Carbon monoxide and water vapour (c) SO2 dos not affect larynx (voice box)
(c) Carbon monoxide (d) NO is more toxic to living tissues than NO2
(d) Nitrogen dioxide 12. The substance which is a primary pollutant?
2. The region which is greatly affected by air pollution is (a) H2SO4 (b) CO
(a) Thermosphere (b) Stratosphere (c) PAN (d) Aldehydes
(c) Troposphere (d) Mesosphere 13. The aromatic compounds present as particulates are
3. The gas responsible for ozone depletion (a) Polycyclic aromatic hydrocarbons
(a) NO and freons (b) SO2 (b) Benzene
(c) CO2 (d) CO (c) Toluene
4. The ozone layer is present in (d) Nitrobenzene
(a) Stratosphere (b) Troposphere 14. Which of the following statement is false?
(c) Thermosphere (d) Mesosphere (a) London smog is oxidising in nature
5. Which of the following is most abundant hydrocarbon (b) Photochemical smog causes irritation in eyes
pollutant (c) London smog is a mixture of smoke and fog
(a) Butane (b) Ethane (d) Photochemical smog results in the formation of
(c) Methane (d) Propane PAN
6. Formation of ozone in the upper atmosphere from 15. Which of the following chemical, harmful to ozone, is
oxygen takes place by the action of released by chlorofluoro carbon
(a) Nitrogen oxides (b) Ultraviolet rays (a) Sulphur dioxide (b) Fluorine
(c) Cosmic rays (d) Free radicals (c) Chlorine (d) Nitrogen dioxide
7. Ozone is an important constituent of stratosphere 16. Which of the following acts as a sink for CO?
because it (a) Plants
(a) Destroys bacteria which are harmful to human life (b) Haemoglobin
(b) Prevents the formation of smog over large cities (c) Microorganisms present in the soil
(c) Removes poisonous gases of the atmosphere by (d) Oceans
reacting with them 17. The greenhouse effect is caused by
(d) Absorbs ultraviolet radiation which is harmful to (a) CO2 (b) NO2
human life (c) NO (d) CO
8. Which of the following is not involved in the formation 18. Ozone layer of stratosphere requires protection from
of photochemical smog? indiscriminate use of
(a) Hydrocarbon (b) NO (a) Baloons
(c) SO2 (d) O3 (b) Pesticides
9. Formation of London smog takes place in (c) Atomic explosions
(a) Winter during day time (d) Aerosols and high flying jets
(b) Summer during day time 19. The non-viable particulate among the following is
(c) Summer during morning time (a) Dust (b) Bacteria
(d) Winter during morning time (c) Moulds (d) Fungi
10. Which forms the part of hazy fumes of photochemical 20. Which of the following causes lung cancer
smog (a) Textiles (b) Asbestos
(a) SO2 (b) Nitrogen dioxide (c) Both (a) and (b) (d) Paper
(c) PAN formation (d) Aldehydes
108 ENVIRONMENTAL CHEMISTRY

21. The greatest affinity for haemoglobin is shown by 26. Eutrophication causes reduction in
which of the following (a) Dissolved oxygen (b) Nutrients
(a) NO (b) CO (c) Dissolved salts (d) All the above
(c) O2 (d) CO2 27. BOD is connected with
22. The false statement among the following is : (a) Microbes and organic matter
(a) The average residence time of NO is one month (b) Organic matter
(b) Limestone acts as a sink for SOx (c) Microbes
(c) SOx can be removed from flue gases by passing (d) None of these
through a solution of citrate ions 28. Water is often treated with chlorine to
(d) Ammonia acts as a sink for NOx (a) Remove hardness
23. The substance having the largest concentration in acid (b) Increase oxygen content
rain? (c) Kill germ particles
(a) H2CO3 (b) HNO3 (d) Remove suspended
(c) HCl (d) H2SO4 29. The type of pollution caused by spraying of DDT
24. Phosphate pollution is caused by (a) Air and soil (b) Air and water
(a) Sewage and agricultural fertilizers (c) Air (d) Air, water and soil
(b) Weathering of phosphate rocks only 30. Which is true about DDT
(c) Agricultural fertilizers only (a) Greenhouse gas
(d) Phosphate rocks and sewage (b) A fertilizer
25. Phosphate fertilizers when added to water leads to (c) Biodegradable pollutant
(a) Increased growth of decomposers (d) Non-biodegradable pollutant
(b) Reduced algal growth
(c) Increased algal growth
(d) Nutrient enrichment (eutrophication)
ENVIRONMENTAL CHEMISTRY 109

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ENVIRONMENTAL CHEMISTRY
110 ANSWER KEY

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CHAPTER - 13: s- BLOCK

Exercise - 1: Basic Objective Questions

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1. (b) 2.(a) 3. (b) 4. (c) 77. (b) 78. (b) 79. (c) 80. (b)
5. (c) 6. (a) 7. (b) 8. (c) 81. (c) 82. (a) 83. (a) 84. (a)
9. (a) 10. (b) 11. (b) 12. (b) 85. (c) 86. (a) 87. (b) 88. (b)
13. (a) 14. (a) 15. (b) 16. (c) 89. (a) 90. (c) 91. (d) 92. (a)
17. (c) 18. (b) 19. (d) 20. (b) 93. (b) 94. (a) 95. (c) 96. (b)
21. (c) 22. (a) 23. (c) 24. (b) 97. (a) 98. (c) 99. (c) 100. (b)
25. (d) 26. (d) 27. (d) 28. (a) 101. (d) 102. (b) 103. (a) 104. (c)
29. (d) 30. (a) 31. (b) 32. (d) 105. (d) 106. (c) 107. (a) 108. (a)
33. (d) 34. (d) 35. (d) 36. (a) 109. (c) 110. (c) 111. (c) 112. (a)
37. (c) 38. (b) 39. (c) 40. (a) 113. (b) 114. (b) 115. (a) 116. (a)
41. (d) 42. (a) 43. (b) 44. (d) 117. (c) 118. (c) 119. (a) 120. (a)
45. (a) 46. (c) 47. (d) 48. (d) 121. (c) 122. (d) 123. (c) 124. (c)
49. (a) 50. (d) 51. (d) 52. (a) 125. (b) 126. (d) 127. (c) 128. (a)
53. (d) 54. (c) 55. (d) 56. (b) 129. (d) 130. (c) 131. (b) 132. (a)
57. (b) 58. (a) 59. (c) 60. (a) 133. (a) 134. (c) 135. (a) 136. (b)
61. (a) 62. (b) 63. (b) 64. (a) 137. (b) 138. (a) 139. (a) 140. (c)
65. (c) 66. (d) 67. (b) 68. (d) 141. (a) 142. (c) 143. (d) 144. (a)
69. (b) 70. (c) 71. (d) 72. (c) 145. (c) 146. (d) 147. (c) 148. (a)
73. (a) 74. (d) 75. (c) 76. (d) 149. (d) 150. (c)
ANSWER KEY 111

Exercise - 2: Previous Year Questions Exercise - 3: Achiever’s Section

DIRECTIONS FOR USE- DIRECTIONS FOR USE-

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1. (a) 2. (c) 3. (d) 4. (d) 1. (d) 2. (c) 3. (d) 4. (d)

5. (a) 6. (a) 7. (b) 8. (d) 5. (d) 6. (b) 7. (d) 8. (c)
9. (b) 10. (c) 11. (d) 12. (b) 9. (c) 10. (c) 11. (a) 12. (b)
13. (b) 14. (d) 15. (d) 16. (a) 13. (d) 14. (d) 15. (b) 16. (d)
17. (d) 18. (b) 19. (c) 20. (b) 17. (a) 18. (b) 19. (a) 20. (a)
21. (c) 22. (d) 23. (b) 24. (c) 21. (a) 22. (b) 23. (c) 24. (a)
25. (d) 26. (a) 27. (a) 28. (d)
25. (a) 26. (c) 27. (a) 28. (a)
29. (b) 30. (c) 31. (a) 32. (d)
29. (c) 30. (b)
33. (a) 34. (c) 35. (d) 36. (c)
37. (d) 38. (b) 39. (b) 40. (c)
41. (c) 42. (a) 43. (d) 44. (a)
45. (a) 46. (a) 47. (d) 48. (b)
49. (c) 50. (b)
112 ANSWER KEY

CHAPTER - 14: p-BLOCK (GROUP 13 AND 14)

Exercise - 1: Basic Objective Questions

DIRECTIONS FOR USE-

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1. (c) 2. (a) 3. (a) 4. (c) 77. (d) 78. (b) 79. (a) 80. (a)
5. (d) 6. (d) 7. (b) 8. (b) 81. (a) 82. (a) 83. (d) 84. (b)
9. (d) 10. (a) 11. (d) 12. (a) 85. (a) 86. (d) 87. (c) 88. (b)
13. (d) 14. (a) 15. (d) 16. (a) 89. (a) 90. (c) 91. (a) 92. (a)
17. (c) 18. (a) 19. (a) 20. (d) 93. (d) 94. (c) 95. (d) 96. (d)
21. (c) 22. (c) 23. (a) 24. (b) 97. (a) 98. (d) 99. (d) 100. (b)
25. (c) 26. (b) 27. (b) 28. (d) 101. (b) 102. (b) 103. (c) 104. (d)
29. (c) 30. (c) 31. (d) 32. (a) 105. (d) 106. (b) 107. (b) 108. (d)
33. (b) 34. (a) 35. (a) 36. (a) 109. (b) 110. (d) 111. (b) 112. (c)
37. (b) 38. (a) 39. (a) 40. (c) 113. (a) 114. (b) 115. (a) 116. (a)
41. (d) 42. (c) 43. (a) 44. (d) 117. (a) 118. (c) 119. (c) 120. (c)
45. (a) 46. (b) 47. (a) 48. (d) 121. (c) 122. (c) 123. (d) 124. (b)
49. (c) 50. (b) 51. (b) 52. (c) 125. (a) 126. (c) 127. (a) 128. (c)
53. (b) 54. (a) 55. (b) 56. (c) 129. (d) 130. (d) 131. (c) 132. (d)
57. (d) 58. (d) 59. (a) 60. (b) 133. (d) 134. (b) 135. (d) 136. (c)
61. (a) 62. (b) 63. (d) 64. (b) 137. (a) 138. (a) 139. (a) 140. (c)
65. (d) 66. (b) 67. (c) 68. (d) 141. (c) 142. (b) 143. (b) 144. (d)
69. (b) 70. (b) 71. (a) 72. (c) 145. (d) 146. (b) 147. (d) 148. (d)
73. (c) 74. (c) 75. (a) 76. (c) 149. (d) 150. (d)
ANSWER KEY 113

Exercise - 2: Previous Year Questions Exercise - 3: Achiever’s Section

DIRECTIONS FOR USE- DIRECTIONS FOR USE-

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1. (b) 2. (c) 3. (a) 4. (a) 1. (a) 2. (a) 3. (d) 4. (b)

5. (b) 6. (b) 7. (c) 8. (a) 5. (b) 6. (c) 7. (a) 8. (a)
9. (c) 10. (c) 11. (b) 12. (b) 9. (a) 10. (a) 11. (c) 12. (b)
13. (b) 14. (c) 15. (b) 16. (b) 13. (c) 14. (c) 15. (c) 16. (a)
17. (a) 18. (c) 19. (c) 20. (a) 17. (d) 18. (a) 19. (b) 20. (c)
21. (a) 22. (a) 23. (a) 24. (c) 21. (c) 22. (a) 23. (a) 24. (d)
25. (b) 26. (a) 27. (d) 28. (d) 25. (a) 26. (b) 27. (c) 28. (b)
29. (c) 30. (c) 31. (a) 32. (a) 29. (d) 30. (c)
33. (c) 34. (a) 35. (c) 36. (b)
37. (d) 38. (a) 39. (d) 40. (a)
41. (b) 42. (b) 43. (a) 44. (d)
45. (b) 46. (d) 47. (b) 48. (a)
49. (c) 50. (d)
114 ANSWER KEY
CHAPTER - 15: ENVIRONMENTAL CHEMISTRY
Exercise - 1: Basic Objective Questions

DIRECTIONS FOR USE-

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1. (d) 2.(d) 3. (b) 4. (c) 77. (c) 78. (a) 79. (b) 80. (b)
5. (c) 6. (d) 7. (c) 8. (b) 81. (d) 82. (c) 83. (c) 84. (a)
9. (c) 10. (b) 11. (a) 12. (a) 85. (c) 86. (d) 87. (a) 88. (a)
13. (b) 14. (c) 15. (a) 16. (a) 89. (d) 90. (b) 91. (c) 92. (a)
17. (c) 18. (b) 19. (a) 20. (c) 93. (c) 94. (a) 95. (c) 96. (a)
21. (b) 22. (c) 23. (d) 24. (d) 97. (c) 98. (a) 99. (b) 100. (c)
25. (a) 26. (b) 27. (d) 28. (c) 101. (c) 102. (b) 103. (c) 104. (a)
29. (b) 30. (c) 31. (b) 32. (a) 105. (a) 106. (b) 107. (a) 108. (d)
33. (d) 34. (b) 35. (a) 36. (a) 109. (a) 110. (d) 111. (b) 112. (d)
37. (c) 38. (b) 39. (a) 40. (a) 113. (c) 114. (c) 115. (b) 116. (c)
41. (c) 42. (d) 43. (d) 44. (c) 117. (b) 118. (b) 119. (c) 120. (a)
45. (a) 46. (d) 47. (c) 48. (a) 121. (b) 122. (a) 123. (a) 124. (c)
49. (d) 50. (c) 51. (c) 52. (c) 125. (d) 126. (c) 127. (c) 128. (a)
53. (a) 54. (b) 55. (c) 56. (d) 129. (a) 130. (c) 131. (a) 132. (b)
57. (b) 58. (c) 59. (d) 60. (d) 133. (a) 134. (c) 135. (c) 136. (d)
61.(d) 62. (b) 63. (d) 64. (a) 137. (d) 138. (b) 139. (a) 140. (c)
65. (d) 66. (c) 67. (a) 68. (d) 141. (c) 142. (b) 143. (a) 144. (a)
69. (b) 70. (a) 71. (a) 72. (b) 145. (c) 146. (b) 147. (c) 148. (c)
73. (d) 74. (b) 75. (a) 76. (b) 149. (b) 150. (b)
ANSWER KEY 115

Exercise - 2: Previous Year Questions Exercise - 3: Achiever’s Section

DIRECTIONS FOR USE- DIRECTIONS FOR USE-

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1. (d) 2. (b) 3. (a) 4. (d) 1. (c) 2. (c) 3. (a) 4. (a)

5. (d) 6. (a) 7. (c) 8. (d) 5. (c) 6. (b) 7. (d) 8. (c)
9. (c) 10. (c) 11. (a) 12. (c) 9. (d) 10. (b) 11. (b) 12. (b)
13. (b) 14. (a) 15. (b) 16. (a) 13. (a) 14. (a) 15. (c) 16. (c)
17. (c) 18. (c) 19. (d) 20. (b) 17. (a) 18. (d) 19. (a) 20. (c)
21. (d) 22. (c) 23. (a) 24. (b) 21. (b) 22. (a) 23. (d) 24. (a)
25. (a) 26. (a) 27. (a) 28. (d)
25. (d) 26. (a) 27. (a) 28. (c)
29. (d) 30. (c) 31. (a) 32. (a)
29. (d) 30. (d)
33. (c) 34. (a) 35. (d) 36. (a)
37. (b) 38. (c) 39. (b) 40. (d)
41. (d) 42. (a) 43. (a) 44. (a)
45. (c) 46. (c) 47. (b) 48. (b)
49. (b) 50. (a)
MASTER INDEX
VOLUME 1:
Structure of an Atom
Periodic Properties
Chemical Bonding
Mole & Equivalent concept

VOLUME 2:
Redox Reactions
Gaseous State
General Organic Chemistry
Hydrocarbons
Hydrogen

VOLUME 3:
Thermodynamics and Thermochemistry
Chemical Equilibrium
Ionic Equilibrium

VOLUME 4:
s- Block
p-Block (group 13 and 14)
Environmental Chemistry
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