‘erro: — _ _ Chemistry

Ertroduction

Theuniverse is made up of very large number of substances. If this vast

array of substance is examined more
closely, it is found that they are made up of some basic substa
nces which were given the name elements and
compounds.

As weall know that elements, compounds and mixtur

es are combinedly known as matter.
All the matter around us is not pure. In fact, matter around
usis of two types:
(i) Pure substance and

(ii) Mixtures
Let us now discuss, pure substances and mixturesin little more detail.

Pure substances

A pure substanceis made up of only onekind of particles. These particles may be either atoms or molecules.
Thus, A pure substance may also be defined as a material which contains only one kind of atoms or
molecules.

Based uponthe nature of the constituent particle pure substanceis of two types, i.e., elements and compounds.

A pure substance which is madevp of cily one fart of atomis called an element while that which is made up of
only one kind of molecule is called a cor pourid

A pure substanceis uniform or homogenous thicughout becauseit consists of only one kind ofparticles. These
particles are similar to one anotherand cannot be separated into simpler particles by any physical process.

For example, water is a pure substance becauseit has uniform composition throughout. It consists of only one
kind of particles called water molecules which cannotbe separated into its constituents (hygirGGgn'‘ahdBrygen)
a s oe
by any simple physical process.
© Library Tary )@=
+

i Impure substances - mixtures \3\\ S1|O/*/

A mixture is a material which contains two or moredifferent kinds of particles (atoms or mol ecules) whichdo not
substances. The
react chemically but are physically mixed together in any proportion. Thus, mixture are impure
the mixture. For example,
pure substances presentin a mixture are called the components orthe constituents of
ide) j water, both of which are
in ressubstances,;, thethe solution of
‘ pure
i{ we dissolve some commonsalt (sodiumchloride)
‘ : :
by simple iy
mixing .
of common salt we
id water
é and
common salt in water is knownas a mixture. It has been obtained
without any chemical reaction.
oo, . ition. Therefore, no definitee formula
A mixture has a variable composition, i.e., does not haveafixed composition. Therefore, no de

can be given to a mixture. Along with this, a mixture does not have a fixed melting point orafixed boiling point.
 aNSE N |
AN
CUM AE seera0: V2 4 b eee Vv
Class |renee:
MELE

py Noon
Matter
, (Solid, Liquid or Gas)
{
| |
Pure Substances i Mixtures
Substance which consist of same (No fixed composition)
type of particles.. Substance which contains
| different typeof particles, not in a
| 1 fixedratio.

Elements Compounds | |
Cannot be broken Have fixed composition,
down into simpler can be broken down into Homogeneous Heterogeneous

6
substances elements by chemical or Uniform composition Non-uniform composition
electrochemical reactions. for example - salt in for exdmple, iron filling

7
For example, water, water, sugar in water, and sulphur, sugar and
sugar,salt, etc. sulphur in carbon sand, salt and sand,

mem
disulphide, waterin iodized salt, wood, blood,
alcoholetc. waterin oil etc. :

a
| |

a
Metals Nomnletat Metalloids Solutions Suspension Colloids
me:

~~
ee some, telies of source ieee of bonding
mercury, sulphur, antimony, . . :
etc.) chlorine, etc.) etc.) Organic Inorganic Covalent Ionic .
(Urea, (Carbon (Carbon (Sodium chloride,
glucose, dioxide, dioxide) calcium carbonate)
starch) water, salt)

Whyare composite materials often used instead of single material?

Explanation
Composite material are those that combine the properties of twoconstituents. In order to get the exact properties
neededfor particular job. For example,
(a) Steel: It is used to makerust free, unbreakable utensils.

I ia sth: nhs
(bs) Bone is composite material.
(c) Wood consists of cellulose mixed with 'Lignin' whichis largely responsible for the strength of the wood.
ae pala sa ans — -. ae eh. a

‘Rdbert Boyle was the first scientist who used the term element in 1661. Antoine Laurent Lavoisier
(1743-1794), a French chemist wasthefirst to give a useful definition of an elementas follows.
An elementis defined as the simplest form or the basic form of a pure substance which can neither be broken
into nor built up from simpler substances by any physical or chemical method. For example, iron is an element
because we maybreakit into pieces, as small as possible, but the chemical formulaof all pieces will be same as
that of iron.
This definition given aboveis not considered to be absolutely correct now a days. This is because after the
discovery ofradioactivity, it has been found that elements can be brokeninto simpler substance. Furthermore,
a number of elements have beensynthesized from simpler substances. Hence, the definition of an element has
been modified as follows.
_ _ ag

An elementis now defined as a pure substancethat contains only one kind of atoms.

22 IT
 ALLER Chemistry

Elements (a) Iron (b) Silver

Anelementis madeup of only one kind of atoms whichare identical in all respects, size, mass, cornposition, ete.
However, atoms of different elements differ in size, mass and composition.
118 Elements have been discovered sofar. Out of these, 90 elements have been aan to occur in nature
whereas the remaining 28 have been synthesized bythe scientists in the laboratories by suitable chernical
reactions and nuclear reactions.
Further, elements are found toexist in all the three states of matter a

Solid elements
Majority of the elements are solids at room temperature. For example. iron, copper, aluminium, silver, gold,
sodium, potassium, sulphur, phosphorus, carbon (graphite or diamond), iodine, etc.
Liquid elements
Mercury and bromineare the only two elements which are known to exists in the liquid state at roorn ternperature.
Gallium and caesium becomeliquid at a temperatureslightly above room temperature (303 K).
Gaseous elements
Eleven elements are gaseous at roomternmperature. These are hydrogen, oxygen, nitrogen, fluorine, chlorine,
helium, neon, argon, krypton, xenon and radon

‘i =P Classification of elements
Classification of elements based on physical and chemical properties
Onthe basis of physical properties, elements have been divided into the following three types:
) (i) Metals (ii) Non-metals and (iii) Metatloid
! Physical properties of metals
' Someimportant physical properties of metal, are described below:
(1) Metals are malleable
This means that metals can be harnmered or tycaten to form thin sheets without breaking. However, all
) metals are not equally malleable. Some are more malleable than others. For example, gold andsilver are
the most malleable metals.
| Uses
(i) Silverfoil is used for decorating sweets
4 (ii) Aluminiumfoils are used for wrapping medicines, cigarettes and food itemslike biscuits, chocolates,
a: etc. Milk bottle caps are also made up of aluminiumfoil.
p (iii) Sheets of iron, copper, aluminium, etc. are used for making utensils, containers and bodies of
5 automobiles.
) (2) Metals are ductile
y This means that metals can be drawnto stretchedinto thin wires. Like malleability, all the metals are not
; equally ductile. Gold andsilver are the most ductile metals. Gold is so ductile that 1 gram ofit can be drawn
) é to form a wire of about 2 kilometer length.
; (3) Metals are good conductors of heat and electricity
yt Generally, metals are good conductors of heat, i.e., they have high thermal conductivity. After silver,
* copper is the best conductor of heat. The cooking utensils and water boilers, etc. are usually made up of
: ; copper or aluminium metals because they are very good conductors of heat. Among metals, lead is the
» § poorest conductorof heat.
f Metals are good conductors of electricity also. That is metals offer very little resistance to the flow of
' 4 electric current and hence show highelectrical conductivity. Silver is the best conductor of electricity
, 3 followed by copper, gold, aluminium and tungsten. |
3 he metals like lead and mercury offer very highresistance to the flowof electric current and hence are
” § poor conductor of electricity
 kk
Class IX ALLEK |

27
(4) Metals are lustrous

Ex
Due to their shining surface, metals are goodreflectors. Silver metal is an excellent reflector of light and é

LLL
henceis used forsilvering of mirrors.
(5) Metals are generally hard

«
Metals are generally quite hard. For example, iron, aluminium, copper, etc. are very hard and hence s
cannotbe cut with a knife. However, metals like sodium and potassium are quite soft and hence can be

\
easily cut with a knife. &
(6) Metals have high tensile strength
6
Metals have a hightensile strength. This means that metals can hold large weights without breaking. For
example, steel (which is an alloy of iron and carbon) is very strong and hence has a hightensile strength. S
° e
Duetothis,it is used for construction ofbiilldings, bridges, railwaylines,chains, girders, machines, vehicles etc. ae
Although mostof the metals are strong, yet some of the metals are not strong. For example, sodium and
potassium metals are not strong and hencehavelowtensile strength. ° €—
(7) Metals are solids at room temperature e-
Except mercury whichis a liquid at room temperature.

aPpPre *
(8) Metals generally have high melting andboiling points
However, sodium and potassium have low melting points; sodium = 371 K, potassium = 336 K, gallium
and cesium becomeliquid at temperature slightly above room temperature (303 K).
(2) Metals generally have high densities
Except sodium and potassium which have low densities.
(10) Metals are sonorous
This meansthat metals make a ringing sound whenhit. It is because of this property that metals are used
for making bells, cymbals (manjira — in Hindi) and wiresof violin, guitar, sitar, tampoora, etc.
Physical properties of non-metals
The physical properties of non-metals are just opposite to those of metals. Some of these properties are

eee
described below:
(1) Non-metals are not malleable but are brittle (break easily)
This meansthat non-metals caret te harnmered or beaten to form thin sheet.
(2) Non-metals are not ductile

H ® ®
This meansthat non-metals cannot be drawnor stretched into wires.
(3) Non-metals are bad conductors of heat and electricity
This meansthat non-metals do not allow heat and electricity to pass through them. Therefore, non-metals
act as insulators. However, there are some exceptions. -

\
For example, diamondisan allotropic form of carbon. It is a non-metal whichis a good conductorof heat

‘= 5 -
i
but bad conductor ofelectricity. Graphite is anotherallotropic form of carbon. It is also a non-metal butis z
a good conductor of heat and electricity. Therefore, graphiteis used for making electrodes of batteries 8
and
drycells. é&
(4) Non-metals are not lustrous but actually have dull appearance x :
However, iodine and graphite are exceptions. They are non-metals which have shining
surface like thatof 7
metals. é<
(5) Non-metals are generally soft 3
Exceptpt diamond
diamond whichis extremely hard. Diamond whichis an allotropic form of carbonis the hardest 45©
~
natural substance known. oe
(6) Non-metals are not strong e*
Non-metals have low tensile strength. 34
(7) Non-metals maybe solid, liquid or gases at room temperature : gj a
Non-metals exist in all the three states of matter ie. solid, liquid and
gas. For example, boron, carbon g ~
sulphur and phosphorus are solid non-metals, bromine is a liquid
non-metal. while thydrogen ‘Sane. 3 e
nitrogen and chlorine are gaseous non-metals. _ ityyay: n 7 3
. nie 8 “«&
 ALLER Chemistry
(8) Solid non-metals have comparatively low melting and boiling points
Except boron, graphite and diamond which have high melting and boiling points.
(9) Non-metals have low densities
Non-metals are generally light elements. That is why have low densities. For example,
density of sulphuris
2 g/cm’.
3s (10) Non-metals exist in different colours
\

‘For example, sulphuris yellow, phosphorusis white, yellow or red, graphite is black, chlorineis yellowish
green, bromineis reddish brown while hydrogen, oxygen, nitrogen are colourless.
(11) Non-metals arenot sonorous
Metallaids -
Elements which have properties ii n between those of resotals and non-metals are called metalloids or semimetals.
For example, Boron(B), Silicon (Si), Germanium (Ge), Arsenic (As), Antimony(Sb), Tellurium (Te), Astatine(At)
and Polonium(Po).
These elements show some properties af metals and other properties of non-metals. For example, they may
looklike metals but arebrittle like non-metals. They are neither good conductorsofelectricity norinsulatorslike
non-metals. They are generally semi-conductors.

Mixture
Mostof the matter around us is not pure but is actually a mixture of two or more pure substances. For example,
air is not a pure substancebut is a mixture of gases such as oxygen, nitrogen, inert gases (mainly argon), carbon
a
dioxide, water vapours, etc. Milk is also not a pure substance becauseit is a mixture of water, fat and proteins.
Types of mixtures
Dependinguponthe nature of components that are. mixed to form mixtures, mixtures have beenclassified into
the following two types:
(1) Homogeneous mixtures {2} Heterogeneous mixtures
(1) Homogeneous mixtures
A homogeneous mixture hasa uniform composition throughout. The components of a homogeneous mixture
are notvisible to the naked eye nor even undera microscope. There are no visible boundaries of separation
between the components of a homogeneous mixture. In other words, a homogeneousmixtureconsists of
only one phase. Thesingle phase of the homogeneous mixture maybea liquid, gas or solid. For example,
(i) A solution of sugar in water is a homogeneous mixturein theliquid phase.
(ii) A mixture of two or more miscible liquids is also a homogeneous mixture in the liquid phase. For
example, a solution of alcohol and water is a homogeneous mixture.
(iii) Alloys are homogeneous mixtures of two or more metals in the solid phase. For example, brass is an
-alloy of zinc and copperand steelis an alloy of iron (98%), carbon (1.5%) and other metals (0. 5%).
Notethatall homogeneousmixturesare called solutions. araed
Ke Go
(2) Heterogeneous mixtures
A heterogeneous mixture does not have a uniform composition throughout. The components of a
heterogeneous mixture areeithervisible to the naked eye or under a microscope. Therefore, there are
visible boundaries of separation between the components of a heterogeneous mixture. In other words,
heterogeneous mixtures have two or moredistinct phases. For example,
(i) A mixture of sugar and sandis a heterogeneous mixture because different parts of the mixture will
havedifferent sugar-sand compositions.
(ii) lodized salt
(iii) Gun powder(sulphur + charcoal + KNO,)
(iv) A suspension ofsolids in liquids is a heterogeneous mixture. For example, a|suspensionof chalk or
sand particles in water is a heterogeneous mixture.

25
 a fixed proportion by mass.
Water (H,O)is acompound
made up of two elements, hyd
rogen (H)
together in a fixed proportion
of 1: 8 by mass.
_ Other examples of compounds
are methane(CH) , silica'or sand (SiO,),
/ (NH aC}}, caustic soda (NaOR), ammo
washing soda(Na,CO.), limeor quic
k lime or-cdldium oxide (CaO)
calcium hydroxide (Ca(OH), potassiumnitrate(KNO,)
meals

, coppersulphate (CuSO,)
potassium permanganate (K
MinO,)items
acid (H,SOa nitric acid(HNO,), gluc
sulphide (FeS), hydrogen chloride or hydrochloric acid(
HC]), sulphu
ose (C,H,,0)), sugar or Cane-sugaror sucr
ose (C,,H,,O,,), etc.
Properties of compounds
a
(1) A compound is made up of the different elements
combined togetherin a fixed proportion by mass.
(2) A chemical compoundis formed asa result of
a chemical change(orreaction) andits properties
are entircg
different from thoseofits constituents. A chemical compoundca
nnotbe formed simply by mixing constituent | le =
elements. It is formed only when a chemicalreaction takes
place between them. For example, simply by
mixingironfilings and sulphur powder, we get a mixture whose
properties are the same as thoseof i!
constituents. However, whenthis mixtu re is heated strongly
a chemical reaction occurs and a new compounr,
called iron sulphideis formed.
- ye

Strongly heat sys

8Fe + 5 Sareea oH &Fes el
- >
lron Sulphur lrovs sulphide © =
(Element) (Element) (Cormpenand) S S|
The properties of iron sulphide this fortesare allogether different from those ofits
constituents, i.e. iron. Vv
and sulphur. For example, when diltite siphuric acidis addedto iron sulphide, a foul smelling gas (having™”
»
the smell of rotten eggs) called hydrogen sulphide (1,5) is evolved. LF
However, wheniron reacts with dilute sulphuric acid, hydrogen gas is formed whichis a colourless, odourlessee | Se
combustible gas. This meansthatiron sulphide does not show the properties ofiron presentin it. .
Similarly, water is not formed when hydrogen and oxygen are simply mixed together.It
is formed only when
an electric spark is passed through this mixture. The properties of water thus formed are altogether we

different from thoseofits constituent elements. For example, hydrogen is a combustible gas while oxyge n
‘¥
is a supporter of combustion. Water on the other handis neither combustible nor a supporter of combustion,
~ Sde * “Ctymp a\Che” stry\O..” ossifoe

it actually extinguishesthefire.
aNf

4 [ ”'B

(3) A compound cannotbe separated into its constituents by simple physical means.
b

For example, water cannotbe separatedintoits constituents i.e. hydrogen and oxygen elements by simple a
"a / Ft (

physical means suchasfiltration, evaporation, distillation, solvent extraction, or using a magnet. This
Nu!

a
:
separation can however, be done by chemical meansi.e. by electrolysis (or passingelectricity)
>

(4) Acompoundhasa definite molecular formula andfixed melting point and boiling point.
(5) Energy in form of heat orlight is usually evolved or absorbed when a compoundis formed. ay
For example, formation of carbon dioxide (CO,) by buming of cokein air or oxygenis always accompanied 3 —S
by evolution of heat. Bee Na
(6) A compoundis a homogeneoussubstance. ae & :
For example, if we take water in a glass or a beaker, every dropofit looks alike’ vende: Homogeneous and —_—_
will show the sameproperties. ‘ s
PN
_
~wASe ier hr BE ew ENE ECE EE
SS

Important note
Compoundsare homogeneousbut mixtures may be homogeneousor heterogeneous.
Homogeneity alone cannot be used to decide between a mixture and a compound. For example, solutions of
commonsalt, sugar, copper sulphate, etc. in water are homogeneous. Butstill they are regarded as mixtures
because of the following reasons:
(i) The commonsalt solution shows the propertiesofits constituents i.e. commonsalt and water.
ii) The constituents of the salt solution i.e. commonsalt and water can be separated by the physical process of
distillation.
eee! =

\Gii” The composition of the salt solutionis variable. In other words, different amountsofsalt can be dissolved in
the same amountof water to get solutions having different compositions. Thus, a salt solution does not have
a definite formula.
\iv)"Saltsolution does not have a fixed boiling point.
2. Non-stoichiometric compounds
Molecules (constituting units of compounds) which havedefinite atomic composition are referred as stoichiometric
compounds. For example, CH,, H,O, NH,, etc.
Certain materials in which atomic compositionis variable are called non-stoichiometric compounds. For example,
the composition of cuproussulphide may vary from Cu, ,S to Cu,S.
Cur — Lat
~ Non-stoichiometry ii s commonfeature of sulphides and oxides of transition metals.
Types of compounds — a
All the compounds may bedivided into the following two categories:
{1) Organic compounds
(2) Inorganic compounds
Organic compoundsare the compounds containing carbon and a few other elements like hydrogen, oxygen,
nitrogen, sulphur, halogens, etc. These were originally obtained only from animals andplants.
Inorganic compounds are the compounds containing any two or more elements out of more than 118 elements
known so far. These are usually obtained from minerals and rocks.
Criteria of purity of compounds
A solid compoundis said to be pureif it has a sharp melting pointi.e. whole ofthe solid melts within a range of
0.5°Cor 0.5 K. Impure solids on the other hand have lower melting points than the pure solids because
esra TE

impurities lower or depress the melting points.

A liquid compoundis said to be pureif it has a fixed boiling point i.e. whole of the liquid distills at a fixed
temperature.
Impureliquids on the other hand have higherboiling points than the pure liquids. This is because impurities
always raise the boiling points. For example, pure waterboils at 100 °C (373K) at one atmospherepressure.
However, sea water is impure because it contains a number of dissolved salts. Thus, the boiling point of sea
water is always higher than 100°C (373 k).

eresena te
List the following‘waters’ in orderofincreasing purity:
Ocean water, rainwater and drinking water.
Explanation
Ocean wateris the least pure becauseit contains a large amountof dissolved compounds. Thatis whyit is not
drinkable and cannot beused for cropirrigation. Drinking water also contains chlorine and some dissolved
compoundsbut not nearly as much as ocean water. Rain water is the purest of three butstill contains some
dissolved gases from the air.
 REY EF
ALLE...
Solutions ©
A solution is defined as a hon geneous mixtur
e of two or more chemically non reactina
substances whic g
composition can be varied withinlimits , f
It maybe notedthat all mixtures are not solutions If a mixture is to ea
be called as solution. then it must satisfy (hye

DE
{
following two conditions
&
ee eT Ee

———
pee fe fee meme femmes =
) The components of a mixture should be non
reactine
(i) Mixture should be honx IQENCOUS
For example, Homogeneous mixture from
our dailyhfe i: vinegar which is a 5
$9 u solution of acetic acid in wate’
Aqueous and non-aqueous solutions

poe pee jeer fe fe fe fee pT a ay Pe PT

Most of the substances are soluble in water. That is why
water 1s sometimes called a universal solvent
>
Asolutionin which water acts as the solvent
is called an aqueous solution while the one
in which anyother qué
acts as the solvent is called a non aqueous solutio
n. For example, the solution of common
salt or Sugar in Water
is called an aqueous solution. However, soluti
on of bromine In carbon te trachlonde, sulphur in carbon disulphide

pee jee} ee pee ‘oall

iodine in alcohol (tincture of iodine) are ¢
alled non-aqueous solutions
e
Eh Methods of expressing concentration of solutions

a
Following are the various wavsof express Inq
concentration of solutions
1.
e
Mass percent 2 Volume percent 3. Normality €
4. Molanty S. Molality 6. Mole fraction
7. Massfraction 8%. Formality 9. Mole percent e ae

pee
(1) Mass percent (% by weight)
e ¢
The massof solute in grams present in 100g of the solution is termed as the mass

pe polP— pop
percent
Mathematically,

?
* ® een
% b - Weightof thesolute 100 a mass of the solute 100

r
oY weight = Weight of the solution “ 00 on mass:

sj
J
= mass of solution
For example, a 15%solution of urea in water {by mass) means that 15
g of urea is present in 100 gof solution”

KHALEY
Similarly, a 10%solution of NaCl by weight means that 100gof solution contains 10 @
v%S of NaCl

CONCEPTUALCHALLENGE2.3
A syrup is prepared by dissolving 250 gram of sucrose in 150 gramof water Calcula
Some

te the mass perce

Redhak 1,JOR BAe a TPfs

@
Qatar
sucrosein the solution. °

Explanation ~ a
We know that a ‘
Massof solute > i 5

eo K 100 eo I +
: Mass% Massof solution “
However, Massof solution = Massof solute + Mass of solvent = 250 + 150 = 400 g a |
2509x100 r YY
% = Fa
Mass% 400g = 62.5%0 * _|_8
de

(2) Volume percentage (%by volume) ~ |. t

It may be defined as the volumeofsolute in ml present in 100 mlof the solution z -'
Volumeof the solute 00 4&
.. wile 6
9 N ES ‘ 7)
bby wohame Volume of the solution ae | 5
For example, a 20%solution of acetic acid (by volume) means 20 mi of acetic acdispre os Or pny of ~y t
solution. nS 3
Find the volume percentage of a solution, in which 20 mlof acetic acid is dissolved in 100 ; as Ss y
Volumeofsolute 8 ekih
Volume of
% by volume = L e solution = 00 = 20%
100 x 100 = 20% a sz
“___ %

ereERIS
fa
\y
LER Chemistry
Ele
Solubility

Solubility
Vhe maxi >
mMarnimum «amount ol sSs. olute2 W
| i
QramsSs which’
i SS
can be dissolved in ] 00 Qyaims of the Ss
3 solveo nt {
ata i
given
?

th if 2s | t 2 1 in Jal al S hve { a ta hat particular

le Mpe
a rature: t & ) for .1 n as t nN < t
Saturated Ss { \
Somuon is ( Ce \\ >
1 S Calec tl « \ | {y oO {
Ss C y| 1 S Olute Solver

For example,
A maxim ” of 36
coon 36 grams
grams of of commonsalt
c (sodiumchloride ) can be dissolved in 100 gramsof water at 20°C (or
293 , therefore, the solubility of commonsalt in waterat 20 °C (or 293 K)is 36. quai
Various factors that effect solubility BLACK mr NT be “TI "

(i) Effect of temperature

solids, gases becomeless
ae
Most solids and liquids are, more soluble in water at higher temperatures. Unlike
r being heated. As the temperature
soluble
__ as the temperatureincreases. This can be witnessed by obs erving wate
gases are expelled.
increases. the watertends to fizz somewhat as the dissolved

PTSeeeee
emforaquatic life?
Howhigh temperature inlakes could be a probl

Explanation
cause fish kills. The lowersolubility of
a dangerfor aquatic animals and may
High temperature in lakes can be -
er temp erat ures Can lead to an oxygen-depleted lake.
oxygen at the high
(ii) Effect of pressure
dissolve more gases in
ure. When you incre ase the pressure, you can usually
press
Solubility also depends on e because the contents of the
can
soda can. They are able to keep thefizz insid
the liquid. Think about your
are under higher pressure.
(iii) Nature of solvent nds to larger extent tha
n the
dissolve polar ionic compou
ven ts wit h hig h val ue ofdielectric constant can
Sol
.
e of dielectric constants
solvents with lowvalu

(iv) Nature of solute ). Non-polar compound

s
mo re sol ubl e in wat er(i.e., a polarsolvent
polar compound) are
lonic compounds(or ves like]
nzene. {Like dissol
-polar solvents like be
are moresoluble in non
rticles ered sugar
(v) Size of solute pa Fo r ex am pl e, it is easier to dissolve powd
e solubilit y.
e particles greater is th
Smallerthe size of th
1
ticles % Solubility ;
ar. Size of solute par
than granules of sug

(vi) Mechanical stirri

ng ng satel spoon. |
ex am pl e, sug ar dis solves faster on stirri
For
increases solubility. in pressure
Mechanical stirring cted by changes
remains unaffe
y of sol ids in liquids, however,
The solubilit
AF ith its help,
Solubility curves lity curves: en
of sol ubi lit y wit h tem perature are called solubi
the variation
The graphs which show temperature can be
find out. Je

solubility of any so
lu te at a pa rt ic ul ar 29
 Y. &. os

ppL-fffj\-TELLL eerhs
1’
CaSO,

0 10 20 30 40 50 60 70 80 90100
Temperature (°C)
Graph between solubility and temperature
Solubility of gasesin liquids
The gases are usually soluble in water as well in other solvents to a certain extent. Thesolubility of a gasin liquid
dependson(i) nature of the gas, (ii) the pressure applied, {iii) temperature and (iv) the nature of the liquid which SS

is taken as solvents.
The solubility of gas in liquid is defined as the mass ofa gas dissolvedin a given volumeof a liquid at constant |
temperatureis directly proportionalto the pressure of the gas in equilibrium with theliquid. This is known as

a
‘3

Henry's law
So, if m be the mass of gas dissolved per unit volume ofa solvent at pressure P then,
m oP at constant temperature
ri = KP whereK is proportionality constant
In terms of mole fraction
x=K,P
x — mole fraction of gas «|
P — partial pressure of gas over the solvent a wi}

The solubility of gases in liquids increases on decreasing the temperature, or decreases on increasing ‘he @. |
temperature. For example, water contains dissolved oxygen, when wateris boiled, the solubility of oxyeon reel
water decreases and the excess oxygen escapes in form of bubbles. ARR |
/p

of ELA

For example, In sea more water animal species are found in deep sea as dissolved oxygen is more. ~
Thesolubility of gases in liquids, however, increases on increasing the pressure and decreases on decr etre 2
pressure. For example, during manufacture of cold drinks, carbon dioxideis dissolved in water und). >» &

A suspension is a heterogeneous mixture in whichthe solute particles do not dissolve but re : 7 ie AN

throughout the bulk of the medium. ‘
Please note that suspensionsare formed by only those substances which are insoluble in wea ‘
Note: Properties of suspensions are discussedin foundation module. «

1 ONE TOMEI Ga ay a
/
[
SB
Pp
‘ELE a
Chemistry
Colloidal solution
Solutions in whichthesize of the
particles lies in between those of
Colloidal solutions or simply true Solutions and suspensions are
colloids. called
,
Particle size < 1nm
> 1000 nm

True solution Colloidal solution Suspension

Particle size of a true solution, a colloidal
solution and a suspension.z
Due to relatively smaller size
of particles, these mixtures appearto be homog
heterogeneous. Since the coll eneousbut actually they are
oidal solutions are heterogeneous in nature, there
true solutions, the term“sol” is fore, to distinguish them from
usedin place of solution.
Emulsions
Colloidal sols in which both the dispersed phas
e and the dispersion medium areliquids are calle
d emulsions.
(i) Oil-in-water emulsions: In these emulsions,oil
is the dispersed phase and wateris the dispersion medi
um.
(ii) Water-in-oil emulsions: In these emulsions, wateris
the disper sed phase andoil is the dispersion medium.
These emulsions are usually prepared by shaking oil
and water vigorously. However, these emulsions of two
pureliquids all usually not stable.
The substances whichare added to stabilize emulsionsar
e called emulsifiers or emulsifying agents. These
stabilize the sols by reducing the surface tension
of wa ter. For example, milk is oil-in-water type emulsion, in
whichliquid fat is dispersed in water and milk
protein 1 actalbuminis the emulsifying agent
Applications of colloids in everydaylife
Colloids play a very significantrole in nature andin our daily life.
Someof the important applicationsofcolloids
are discussed below:
(i) Medicines: Most of the medicines usedareinthecolloidal form because in
this form, they are moreeasily
assimilated due to large surface area and henceare moreeffective.
For example,
a) Argyrolisa silver sol used as an eyelotion
{o) Colloidal antimonyis used for curing kalazar.
(c) Colloidal gold is used as an intramuscular injection.
\ (d) Milk of magnesia, whichis an emulsion, is used as an antacid for reducing acidity in the stomach.
(ii) Food articles: A numberof food articles that we eat are colloidalin nature. For example, milk, butter,
ice
creams, fruit juices, halwa, etc.
NY ct SO I RS re

(iii) Fog, mist and cloud:In winters,at night, the moisture of the air condenseson the surfaceof dust particles
formingfine droplets. These droplets are colloidal in size and hencecontinue tofloatin the air in the form
of fog or mist.
Clouds are aerosols consisting of small droplets of water suspendedin theair. In the upper atmosphere
where the temperatureis low, they condense together to form bigger drops which come down in the form
of rain. Rain is also caused when two oppositely charged clouds meeteach other.
(iv) Artificial rain: Artificial rain can be caused by sprayingelectrified or oppositely charged colloidal dust,
sand particles over a cloud. The colloidal water particles present in the cloud will get neutralized and
‘coagulate to form bigger water drops causing artificial rain. Artificial rain can also be caused by throwing
commonsalt on the clouds, asit is an electrolyte and brings about coagulation of waterparticles.

SE
AS
cumnieowt 3]
=
 aT SSS SERSES ES
(v) Formation of Delta: River water contains charged colloidal particles of clay, sand and manyother materwls
Sea wateris a very big store-house of a variety of electrolytes dissolvedin it. As soon asriver water comes 4
in contact with sea water, the electrolytes present in sea water coaqulate the suspended colloidal particlesy
whichultimately settle downat the point of contact. Thus, thelevel of the river bed rises. As a result, water

FP? P97 & ON.

adopts a different course and delta is formed in due course of time.
It is so called because the heap formedhas a shapesimilar to the Greek letter A (delta). In other words, (A

~S
delta is formeddueto silting of theestuary (i.e. deposit of sediment at the mouth of theriver).

VEEDEEP eee
FEEEEEANAANAN
SUITE ENNNNNNN
VETIEELEE RNNNNNN
CALLE 3
VAthhts.:
~ Sand &clay particles
coaqulated by salts of
VACLVAS 8 we sea Water
SILA Soe oe
HS NNANNAN

PF onnation of Delta

oP
(vi) Blue colour of the sky: This is due to the scattering of light by colloidal dust particles present in air
(Tyndall effect). This is explained by Rayleigh scattering according to which if diameter of particles is
smaller than the wavelength of the incident radiation, scattering takes place. As blue colour of the white @
sunlight has minimumwavelenath, it shows more intense scattering. Hence, sky looks blue.
Similarly, sea water looks blue due to scattering of light by the colloidal impurities present in sea water.
(vii) Tail of comets: It is seen as a Tyndall cone due to the scattering of hght by the tiny sold particles left by the £
cometin its path. «€

(vii) Blood: It is a colloidal solution of an albumunoid and the bleeding stops on applying ferric chloride solution
due to coagulation of blood forming a clot.

Ker
(ix) Cleansing action of soap: Soapsolutionis colloidal in nature. It removes the dirt particles either by @
adsorption or by emulsifying the greasy mattersticking to the cloth.

» %
&x) Smoke screen: In warfare, smoke screensare used which are nothing but colloidal dispersion of certain
substances (For example, titanium oxide) in the air.
: 1s
& 1 ;

ze
.
Separation of mixtures
ie
Pos,
“ |
; - ti
; order to obtain these useful substances, i “2.
Many mixture contain useful substances mixed with unwanted matenials. In
chemist often have to separate them fromthe impurities. Chemists have developed manydifferent methods of =. st
separation. Use of method depends on whatis in the mixture and the properties of substances. It also depends “ os
ance
dl it ond a :
on whether the substance to be separated aresolid,liquid or gas.
|
jly5,
Separation of solid i - solid i
i mixtures
a™ - . 4

(1) Solvent extraction oo

‘ : hg}
| t
used. For example, a mixtu’- i
In this method of separation, solubility of one component in a solventis
sulphur and sand can beseparated bythis method. Heresulphuris soluble in carbon disulphide (CS, ar. ax %4 -
eS
sandis insoluble.
gy ohsA

(2) Magnetic separation

NS

©
In this methodof separation, magnetic property of one component is used. For example, mix... sf i-on,
wp

\
by magnet and sand «ti t.chind. a Oy,
ore and sand can be separated by this method. Here ironoreis attracted
B

aX
vie§
aa
>
a“

32 ROEBS PRACT ee
(|
:
 Mixture of iron Bar maanet
filings and sand
—lron filings

Sand

Separation of a mixture ofiron filin

gs and sand
(3) Gravity method

In this method of separation, diff

erence in densities of component is
and chalk powder can be separate used. For example, mixture of sand
d bythis method. Her e, sand being
water whereas chalk powder floa heavierthan chalk powder sinks in
ts on w ater.
(4) Fractional crystallisation
In this method of Separation, diff
erence in solubility of the components in the
example, mixture of potassium nitr same solvent is used. For
ate (KNO.) and sodium chloride (NaCl) can be separa
Here, potass ted by this method.
ium nitrate (KNO,) being more
soluble than sodium chloride (NaC]) in water. whent
solution of this mixture is subje he aqueous
cted to heating and subsequent cooling the more solubl
(KNO,) remainsin the solution, less soluble sodium chloride
(NaCl) crystallizes out first.
e potassium nitrate

CONCEPTUAL CHALLENGE2.5
A mixture contains two components A
and B. The > solubilities of A and B in water neartheir
boiling point are 10
grams per 100 ml and 29 per 100 ml resp ectively
. Howwill you separate A and B from this mixture?
Explanation
Fractional crystallization. When th saturated hot
solution of this mixtureis allowed to cool. the less soluble
component B crystallizes out first leavin mM tno ire soluble compon
2 dha
ent A in the mother liquor
Separation of solid - liquid mixtures
(1) Sedimentation and decantation

In this methodof separation, high density of insoluble solid component is

used. For example. mixture of
sand andwater can be separated by this method. Here sand being heavier settles
at the bottom and liquid
is Slowly transferred into another container

Sand + Water

N Sediment
Fhe q
Clear water
Susy

Sand sediment

(a) Sedimentation (b) Decantation

(2) Filtration
7.The processof filtration is used to separate insoluble solid
idecomponent
) of a mixture
ire from the > sokube
habvt
ony
Component
wy sort

Ina Given solvent

33
 pe be eee be
rem
me
Class IX ALLER

ee ee eb
For example,

am

>
Liquid

ES
A mixture containing naphthalene and urea can be separated by Filter_, [4

ot
paper

eo npmp
this technique. Ureadissolves in water while naphthalene remains

bess
insoluble. Urea is recovered from thefiltrate by evaporating water. Perforation
- : . - z.
"\ Buchner
funne

aesuai igHalgp
Sometime for separation purposesthefiltration of a hot solutionis
required. For example, a mixture of anthracene and benzoic acid is

a
separated by dissolving it in hot water andfiltering the hotsolution. To filter pump

1s capeanmane
Benzoic acid crystallizes on cooling while anthracene remains as an Filtrate
insoluble —
——— residue. - through Buchnerfunnel
(a) Filtration
If the water soluble componentof a mixture is appreciallsoluble in ~

.
hot water butonly sparingly soluble in cold water, then to separate Filter paper

-
the mixture,filtration of a hotsolution is required. Thisis carried out
througha fluted filter paper to avoid crystallisation duringfiltration

powaye
and also to remove suspend impurities. If the solutionto be filtered Hot water
is sufficiently large, then filtration is done through a “hot water funnel’ ume
to avoid formationof crystals in the funnel and its stem. The jacket
Filtrate
of the hot water funnel keeps the solution hot in the glass funnel
f Ea &
placedin it.

bey of
Dh)— DomPn prompvePov
ear

2
For example, a mixture of anthracene and benzoic acid is separated Fikration of hot mixture

4)
M
(b) Fittration of hot mixture

PB
by dissolving the mixture in hot water andfiltering the hot solution.

be J
Benzoic acid dissolves in hot water but anthrance cines net. Upon fittration, anthracene remains as a residue on
the filter paper while benzoic acid crystallises fromthe filtrate on cooling.

fare
Be
n
Sometimes, thefiltration is very slow and takes a tong time. In suchcases, filtration is carried out under reduced

‘
bor P
pressure using a Buchnerfunneland water suction pump are shownin figure below.

Separation of liquid — liquid mixture

(1) Vacuum distillation or distillation under reduced pressure

>.
[. hi
This technique ofdistillation is applied to liquids which decompose onheatingto their boiling point. We know 2 =
that the boiling pointofa liquid varies with atmospheric pressurei.e., at reduced pressure the boiling point $ +
of liquid is also reduced andthusliquid distils at low temperature. 3 4 .3
i to
(2) Steam distillation
This is a convenient method forthe separation andpurification of organic compounds(solid or liquid) from : 35
non-volatile organic or inorganic impurities. This method is applicable to only those compoundswhich are ; Ls:
‘ “ 4USE\ M1 Advance. science Caympiods \Chemistry \02-Classifiest
)
volatile in steam, insoluble in water, possess a vapourpressure of about 10 - 15 mm of Hg at 373 K and
fp

contain non-volatile impurities. Some of the compoundswhich can bepurified by this process are essenti:: *° = >
aD

oils, nitrobenzene, chlorobenzene, etc. é gay .

COS
fh
A
fo

[,
ChE Oo Ravan.

(CECE
Howwill you separate a mixture of o-nitrophenolandp-nitrophenol?
Explanation
4
ih
noi ee OnIDD

Steam distillation, o-nitrophenol being volatile distils over along with water while P-nitrophenol ;
2
ie

WING AOA: -
volatile remainsin theflask. ,
gil

BOS BUA
os

34
RSALAE
‘>

4
 Separation of Gas - gas mixtures es
Scomihy
(t) Diffusion
In this method of separation, difference in densit
ies of componentgasesis used. The
gas with lower molecular
weight diffuses faster than the gas with higher molec
ular weight. For example, hydrogen(H,) and metha
(CH,), helium (He) and sulphurdioxide (SO,). ne
‘
(2) Dissolution in suitable solv
ents
In this method of separation, difference in solubility
of component gasesin a given solvent is used. For
example, a mixtu
re of carbon dioxide (CO,) is soluble in potassium
hydroxide (KOH) leaving behind carbon
monoxide (CO). Here, in a mixture of ammonia (NH,)
and nitrogen (N,) ammonia (NH,is soluble in water
and nitrogen (N,) is insoluble.
(3) Preferential liquefaction
In this method of separation, difference in liquefaction of
componentgasesin a given‘solventis used. For
example, a mixture of ammonia (NH,) and hydrogen (H,) can
be separated by this method. Here, ammonia
Gets liquefied under high pressure and hydrogen gasis
left behind.
(4) Fractional evaporation
in this method of separationdifferencein boiling points of the componentgases
is used. For example, when
airis liquefied, the major components of air, nitrogen (N,) and oxygen (O,)
can be separated by subjecting
theliquid to evaporation. Here, nitrogen (N,) has a lowerboiling point and
hence boils off, oxygen (O,) has
a higher boiling point and remains behind.
Separation of liquid - gas mixtures
(1) Heating:In this method of separation, decrease in solubility of a gas with increase in temperatur
eis used.
For example, when a solution containing a gas is subjected to slight heating below theboiling
pointof the
liquid, the gas escapes out leaving behind the liquid component. For example, separation of dissolved
oxygen (O,) in water by heating water.
(2) Loweringthe pressure: In this methodof separation, difference in solubility of gas in theliquid at different
pressureis used. For example, soda water can be separated by this method. Here, when soda waterbottle
is opened, the pressure inside the bottle decreases and carbon dioxide (CO,gas fizzes out of the bottle.
A special method applicabie for all types of mixture is
Chromatography:
The name chromatographyis based on the Greek word chroma, for colour since the method wasfirst used for
the separation of coloured substances foundin plants.
Types of chromatography: The stationary phase can beeithera solid or tightly boundliquid on a solid
support while the mobile phase can beeithera liquid or a gas. Depending uponthe nature ofthe stationary and
the mobile phases, the different types of chromatographic techniques commonly usedaregivenin.

Some commontypes of chromatography

S.No. Type of chromatography Mobile/ Uses
Stationary
phase
1 Adsorption or Column Liquid / Solid |Large scale separations
chromatography
See. ~as “..

Z Thin layer chromatography (TLC) Liquid / Solid |Quallitative analysis (identification and
characterization of organic compound)
3 High performance liquid Liquid / Solid |Qualitative and quantitative analysis
Nag @o \WUAI DY \UO oe + AU Ne ey

chromatography (HPLC)
Gasliquid chromatography (GLC) Gas / Liquid |Qualitative and quantitative analysis
’ Paperor partition chromatography} Liquid / Liquid |Qualitative and quantitative analysis
of polar organic compounds(sugars,
aminoacids) and inorganic compounds.
 —_ fmm mmr femme fmm: fmm po) mT fy eT
JN
Class IX i
Depending upon the principle involved, chromatograp :
ALLEM 4
hy can be divided into the folk wing tworcalega
IQATICS:
ries:
f
(a) Adsorption chromatography 4
(b) Partition chr« »ymatography
Adsorption chromatography; -
G
Principle. This method is based upon the differential adsorp
tion of the various componentsof a mixture on a

cy A & O_®™
suitable adsorbent such as silica gel or alumina. Since some compounds are
more strongly adsorbed than the
other, they will travel through the column at different rates and thus
get separated.
Types of adsorption chromatography
Adsorption chromatography is of the following two types:
() Cohan chromatography (ii) Thin layer chromatography

‘tention factor (R,) values = Il is defined as Distancetravelled by the compound (X)

nae : (Ri) R. =
' Distancetravelled by the solvent from (Y)
Since, the solvent front always moves faster on the TLC

(e
plate than the compounds, R, values are usually
expressed as a decimal fraction.

oe
Partition chromatography:
Principle: Paper chromatography works
on the principle ofpartition thatis it is based upon continuous differen
partitioning of the various components of tial
the mixture betweenthe stationary and the mobile phases. e*
CONCEPTUAL CHALLENGE 2.7
Name the method whichis most
suitable for separation of the follow
ing:
(a) Oxygenfrom liquid air d
(b) Red bloodcell from plasma I
(c) Petrol and kerosene from crude oil e
(a) Coffee grains from coffee solution SI
(e) Pieces of steel from engineoil
(f) Aminoacids fromfruit juice solution
(g) Ethanoland e}ther
Explanation
a
|
(a) Oxygen from liquid air = Fractional distil
lation
(b) Red bloodcell from plasma = Centrifuga &
tion
(c) Petrol and Kerosene fromcrude oil ~ q
= Fractional distillation
(d) Coffee grain fromcoffee solution = Filtration eS
(e) Pieces of steel from engine oil = Magnetic oq
separation
(f) Amino acids from fruit juice solution = Chro ~ q
matograp hy
(g) Ethanol and ether = Fractional distillation ‘on +f ©
oo :
ra.
Some Additional Topics
(1) Normality (N) d - a
Normality of a solution may a
bedefined as the number of
solution. It is denoted by N, gram equivalent of solute Prese
nt per litre of the ©& |
_ a SS _ “ex
Mathematically,
A ¢
N Gramequivalents of solute i .
7.
~ Volumeof the solution in litres : ‘2
‘'S |
. Weightof solute in g — &
Eq. wt.of solute xVolume of Cen TAS
solution in litre
:
4 Strength of solution in G/litre
oN
~ Equivalent weightof solute * )
The unit of normality is equivalent 5° s
lit”.
36 S s:~
8 A
L
a

a
OMIfisor,
a
FMRC APPRIAY Hyin

N = Normal solution
N
ao O5N= Seminormal

N
== 0O.2N= Pentanormal

N
To = 9-1N = Decinormal
LON = Decanormal

aeeeoe
Calculate the normality of NaOHsolution containing 50.0
gm NaOHin5.0 litre solution.
Explanation

Eqquivalent M.W. of NaOH 409

nt weig
wei ht of NaOH =
se e~ ~~
Acidity of bas
|
= 40

No. of equivalents in 50.0 g NaOH = 407

1.25

Normality of NaOHsolution = iva of solut

; Equi cents = lute
Volume of solution inlitres = —
5
= 0.25N
(2) Molarity (M)
Molarity ofa solution is defined as the numberof molesof the solut
e perlitre of solution. For example, a
molar (1 M) solution of sugar meansa solution containing 1 mole of
sugar(i.e., 342 g) perlitre of the
solution.
Thus mathematically,

Number of moles of solute Massof the solute

= —— [No. of moles = ==
Volumeof solutionin litres Molar mass ofsolute
Wt.of solute in gms ‘
or M=
Molecular wt. of solute x Volume of solution in litres
Therefore,unit of molarity is moles lit”. It isthe most common wayof representing the concentration of the
solution.
Relationship between normality and molarity of a solution

Mol.uwt. . ;
Normality = Molarity x = wt Of Normality = Molarity x Acidity of Base or Basicity of acid

where acidity of base = No. of replaceable OH”ion

andbasicity of acid = No. of replaceable H’* ion.

Molarity = Normality x
Mol.wt.
 AN a

a ad foes bee bee beet

Class IX

~
ALLER -

A
0)an a
(3) Motality (m)
Molality of a solution may be defined as the numberof moles of the solute dissolved per 1000g of the
solvent. For example, a 0.2 molal (0.2 m) solution of glucose means a solution obtained by dissolving 0.2
gram mole of glucose in 1000 g (1 kg) of water.
Mathematically, ,
Moles of solute

e
Molality (m) =
Massorsolvent in kilograms

PPEre ry
fj
No. of moles of solute
Molality (m) = x1000

r
Wt. of solvent in gms
Massofsolute in grams 1000
m=
Molecular massof solute ~ Wt. of solventin gms
It is expressed in units of moles kg”. _

PE
The value of normality and molarity varies with temperature as the volumeofsolution containing equivalents

EP
or moles of the solute increases with rise in temperature. However, molality is temperature independent
because here volumeterm is notinvolved.

EF
Followingis the relationship between molarity and molality derived from the formulae of molarity and

T
molality.

Molarity Massof solvent in kg

-
Molality ~ Volumeofsolutioninlitre
(4) Mole fraction (x)
It is defined us the ratio of the number of moles of one component(solute or solvent) to the total number of @.
molesof all the components (solute plus solvent) present in the solution. It is denoted by 'x’. I
¢~—
tk
Moles of solute
Thus, x =
Sotute Moles of solute + Moles of solvent S

tmp
For example, in a solution containing n, moles of solute and n, moles of solvent the mole fraction of solute
(Xone) and mole fraction of solvent (x...) are Ss
ny nz
&
X coke ~ n; +N» , X pent a ny +Npg
©

The sum of the mole fractions of all cormponents present in the solution is always one and has no unit.

Lg —
N»5
«
nj+n, My +N,
2c
Mole fraction of the components is always temperature independent. 2

Thus, in binary solution, if we knowthe mole fraction of one component, the mole fraction of the other
i?
componentcan becalculated. is
CONCEPTUAL CHALLENGE2.9
4.0 g of NaOHis contained in one decilitre of a solution. Calculate molality of solution and mole fraction of |
Om Lan co\Scmr Sere thon
a

NaOH. [At. wt. Na = 23; O = 16: Density of NaOH solution is 1.038 g/cm’]
a€

Explanation
(a) Calculation of molality of solution
7
-

4
Moles of NaOH = 407 0.1 mole
a
Da

Volumeof solution = 1 Decilitre = 100 ml

CASE OA
é>

Weight Of 100 mlsolutionof density 1.038 g/cm* = V xd = 100 x1.038 = 103.8 Q

Rade BOAIFO OLAS

So, the massof the solvent = mass ofthe solution - mass of solute = 103.8-4 = 99.8q
2

/ Moles of solute
, Motality= Kg. of the solvent
”

38 aaneh ntiee
<
>
 0.1 0.1x1000
99.8/1000 99.8 ™
= = = 1.02

(b) Calculation of mole fraction of NaOH.

Moles of NaOH = 0.1 mole

Moles of water in 99.8 g water = 73° = 5.55 mole

Xx , Moles of NaOH 0.1 O.1 0.017

NOHMoles of NaOH + Moles of water 0.14+5.55 5.65 ~
(5) Massfraction
Similar to mole fraction, mass fraction is defined as the ratio of the mass of one component(solute or
solvent) to the total mass ofthe solution (both components). For a binary solution containing two components
A and B, the massfractionsare,
Wa
Massfraction of A = Wa +Wp

Wa
Massfraction of B = Wa +Wp

eededeeal
Calculate mass fraction and molefraction of ethyl alcohol and water containing 9.2 g alcoholin 18.0 g of water.
Explanation
Massof ethyl alcohol = 9.2 g
Molecular mass of alcohol (C,H,OH)= 46 g mol’

Numberof mole of alcohol in 9.2 g = 46 = 0.2 mol

Massof water = 18 g

18
So. numberof moles of water = 13 = 1.0 mole

9.2 92
Massfraction of alcohol =
1849.2 27.2- 0.382
Massfraction of water = 1 — 0.338 = 0.672

0.2 0.2
Xx
dnl = 70402 7 1.2 ~ 2-167
Xwater = 1 - 0.167 = 0.833
(6) Formality (F)
The term formality was first of all used by Pauling to express the concentration of a solution. This is defined
as the number of gram formula weightof ionic solute presentperlitre of the solution.

Moles of the ionic solute Massofthe ionic solute in gram perlitre

horniality, ila Volume ofsolution in litres — Formula massof solute
For example, formality of a solution containing 5.85 grams of commonsalt perlitre of solution is 0.1 or the
solutionis 0.1 formal.
(7) Mole percent
Mole percentfor a solution may be defined as the numberof moles of a component(solute or solvent) in
100 moles ofsolute plus solvent.
Mathematically,
Mole percent = Mole fraction x 100
 SO. CecGuant\ = *
Class IX
For example, mole percentof a solution containing 6 moles of ethanol in 14 moles of wateris calculated as
follows,

Mole fraction ofethanol, Xc,H,04 = => = 0.3

6414
Therefore, Mole percent(ethanol) = 0.3 x 100 = 30 mole %
Classification ofcolloids on the basis of interaction between different phases

i
\
Depending uponthenature ofinteraction between dispersed phase anddispersion medium, colloidsare classified as,
(i) Lyophillic colloids: The dispersed phase hasgreataffinity for dispersion medium, in such cases the

|
\
-
disperse phase doesnoteasily get precipitated and the colloids are quite stable. The solids obtained after

oa” 9 Fm OOO
evaporation of the medium canbeeasily brought back to the colloidal state by shaking the solids with the
dispersion medium.
The colloids are thus reversible, For example, gum, gelatin, starch, proteins and certain polymersin organic
solvents.
If wateris the dispersion medium thenthecolloid is called hydrophillic colloid.
(ii) Lyophobic colloids: The dispersed phase haslittle affinity for the dispersion medium. Thesesols are
relatively less stable. They can be easily precipitated by addition of small amount ofelectrolyte. Once they
are precipitated, they cannot be easily broughtback to thecolloidalstate.
Theyare thus irreversible, For example, gold sol and sulphursol, etc. if water is used as the dispersion
medium. Thesolis called hydrolyophobiccolloid.
Difference between Lyophillic and Lyophobic sols:

S. No. Property Lyophillic Sols Lyophobic Sols

L. Surface tension |Lower than that of the medium. Same as that of the medium.
Viscosity Much higher than that of the Same as that of the medium.
medium.
3. Reversibility Reversible Irreversible

® @
i i
4. Stability More stable Less stable
5. Visibility Particles can’t be detected even Particles can be detected under
underultra microscope ultra microscope.

ao
6. Migration Particles may migrate in either Particles migrate either towards
direction or do not migrate in an cathode or anodein an electric
electric field. field.

2 Tlassification of materials.p65

/
1: Action of Addition of smaller quantity of Coagulation takes place.
electrolyte electrolyte has little effect.

a a /
8. Hydration Extensive hydration takes place. No hydration takesplace.

Classification on the basis of the particles of the dispersed phase /

2

a Multimolecular Colloids ae Associated Colloids

out own

1. They are formed by the They are moleculesof They are formed by the
.

aggregation of a large numberof large size. For example, _|aggregation of large no. of ion in
\Scienu Mama
‘

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 Chemistry

Sa 1. The.most abundant metal in the earth's crustis

(1) Fe (2) Cu (3) Al (4) Au

The most abundant elementin the earth's crust is ~ .
(1) Si (2)c (3) O (4) Ca.
Air is regarded as a mixture because

(1) its pressure may very. (2) its temperature may change.
(3) its volume changes underdifferent conditions. (4) its composition may vary. -
Which of the followingis not true about mixtures?

(1) Mixtures can be homogeneousor heterogeneous.

(2) Componentsin a mixture are always presentin a fixedratio.

(3) Properties of a mixture are the average of its components.

(4) Components of a mixture can be separatedeasily by simple physical methods.

5. Which oftheseis not a mixture?
TOGHH

(1) Oil and water (2) Sand and water (3) Diet Soda (4) All are mixtures.

6. A sample contains two substances and does not have uniform properties. The sampleis,
ee ND GF

(1) a compound {2) a heterogeneous mixture

(3) an element (4) a homogeneous mixture

7. Whichof the following is a homogeneous system?

(1) Muddy water (2) Bread {3) Concrete (4) A solution of sugar in water

8. Select the odd one out.

(1) Hydrogen (2) Oxygen (3) Steam (4) Chlorine

9. A homogeneous system amongthefollowingis

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(1) milk (2) sand in water (3) urea in water (4) benzenein water

10. | Whichofthe followingis insoluble in water?

(1) Benzene (2) Alcohol (3) Acetic acid (4) Sugar
ea te eee eee nesee

11. Whichofthe following is a compound? .

(1) Stainless steel (2) Bronze (3) Graphite (4) Hydrogensulphide
12. Twosubstances A and B whenbroughttogether form a substance C with the evolution of heat. The properties
of C are entirely different from those of A and B. The substanceC is
Q) a compound (2) an element (3) a mixture (4) none of these
13- ‘ Whichofthe following is a characteristic of both mixtures and compounds?
(1) They contain componentsin fixed proportions.

(2) Their properties are the same as those of their components.

(3) Their weight equals the sum of the weights of their components.
(4) Energy is given out when they are being prepared.
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 Class IX
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14. Which ofthe followingis true solution?

(1) Milk (2) Chalk powder in water

(3) Salt solution (4) Blood

15. Solutions with low concentrationofsolutes are,

(1) concentrated 42 dilute (3) solvents (4) none of these

16. Aliquidand a solid together consisting a single phase is known as

_{1solution (2) solute (3) solvent (4) emulsion

17. Amalgam isa solution of
(1) solid in solid (2) solid in liquid (3) liquid in solid (4)liquid jn liquid
18. Whichof the followingis a true solution?
(1) NaClin suiphur dioxide (2)Copper in silver
(3) Salt in petrol (4) Mud in water
19. ~ A solution ofiodine in alcoholis known as
. (1) aqueous solution. (2) alcoholic solution.
(3) heterogeneous solution. (4) tincture of iodine.

_ 20. Solution consists of

(1) solvent (2) solute (3) solutes (4) all of these

21. Solution is a
Jhomogeneousmixture.

(2) heterogeneous mixture.

oa
(3) compoundformed betweensolute ands:aiverit.

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(4) homo as well as heterogeneous mixture.

22. Solid solutionis

(AJ Solid in solid (2) Solid in liquid (3) Solid in gas (4) Liquid in solid
23. The solution of sugar in water contains of Materials p45

(1) free atoms. (2) free ions.

(3)flee molecules.
‘2

(4) free atoms and molecules.

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24. Gun powderisa_

i)

(1) solid-liquid homogeneous mixture (2) solid-liquid heterogeneous mixture

(3) solid-solid homogeneous mixture (4) solid-solid heterogeneous mixture
‘25. Which ofthefollowingis not a solution?
(1) Smoke (2) Air (3) Salt (4}.Agold ring
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26. Whenraisin is placedin waterit esos

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(1) shrinks (2) swells 2) hums a)Sdnsine sn

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27. Out of formality (F), molality(m), molarity(M) and mole fraction(x), which ei dé endentiin te -
he

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(1) M, m (2) F, x (3) m, x Mx.

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 ALLEK — Chemistry
28.
If 100 ml of 1M NaOHis diluted to one litre, the
resulting solution has molarity
(1) M/100 (2) 0.1 M (3) 1M (4) 10M
29. What is: the volume of
water to be added to 200 ml of 18M <
H,SO,solution to get 1.8M H,SO,
solution?
(1) 1800 litres (2) 2000 litres (3) 2000 ml (4) 1800 ml
30. The molari:ty of a. soluti. on prepared by ; 5 7.1
dissolving :
gm of Na,SO, in 100 mlwat eris
(1)2M (2)1M (3) 0.5 M (4) 0.05 M
One molal solution contains

(1) one mole of solute in onelitre of soluti

on. (2) one mole of solute in 1000 gm of the
solvent.
(3) one gram-equivalent in 1000 mlof solut
ions. (4) one gram-equivalent in 1000 gm. if solven
t.
The numberof moles of NaOH present in
10 litres of 1 molar solution is
(1) 10 (2) 1 (3) 0.1 (4) 0.01
How many moles are represented by
24.5 gm of H,SO,?
(1) 2.5 (2) 2.05 (3) 0.25 (4) 25
aR Ay

Which of the following acid has the same molecul

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ar weight and equivalent weight?

ree on

(1) HPO, (2) H,PO, (3) HPO, (4) H,SO,

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35. Find the number of equivalents of solute present

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in 123 ml of 1N KOHsolution.
(1) 123 (2) 12.3 (3) 1.23 (4) 0.123
36. 1000 ml of wateris added to 250 ml of 0.05 N HCIsolution.
Find the nomnality of dilute solution.
(1)1N (2) 0.05 N (3) 0.01 N (4)5.N
37. The molarity of HPO, solutionis 0.05 M. Findits nomnalit
y.
(1)0.15N (2)1.5N (3) 0.03 N (4) 0.3 N
38. A one molar solution is one that contains
SS

(1) 1 g ofthe solute in 1000 g of solvent. (2) 1 g mole of solute in 1000 ml ofsolution.
(3) 1 g mole of solute in 22.4 litres of solution.
ee

(4) 1 g moleof solute in 1000 g of solvent.

39. 4gm of NaOHare dissolved in 500 ml of water. Active mass of NaOH is
(1) 0.1 (2) 0.2 (3) 0.3 (4) 0.4
40. Whichis dimensionless quantity?
(1) Molarity (2) Mole fraction (3) Normality (4) None of these
41. Concentrated Hydrochloric Acid is 36.5% by weight. Whatis the molality of the solution?
(1) 1.575 molal (2) 15.75 molal (3) 157.5 molal (4) 1575 molal
42. The concentration unit which changeswith temperature is
(1) molarity (2) molality
(3) mole Fraction (4) both molality and mole fraction
43. To changethe molal concentration to one half which one of the following should be adopted?
(1) Weight of solute should be doubled. (2) Weight of solvent should be doubled.
(3) Volumeof solvent should be doubled. (4) Weightof the solution should be doubled.

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44. The concentration method applicable to solutes with macro molecules, polymersand ionic solid is
(1) molarity (2) formality (3) normality (4) molality

45. 3.65 grams of HClis dissolved in 180 gramsof water. Whatis the Mole Fraction of water and HCl?
(1) land 9 (2) 9and 1 ‘ (3) .99 and .009 (4) 0.9 and 0.1

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Molarity is expressed in . '
(1) moles/kg (2) g/lit (3) moles/lit (4) lit/mole

Ro
47. The ratio between the numberof moles of a compound andtotal number of moles present in a mixtureis
called
(1) normality (2) molarity (3) mole fraction (4) formality

48. The unit of mole fraction of a componentof a solutionis a

(1) Moles/litre (2) Moles/Kg (3) No units (4) Grams/litre
49. 9.8 g of H,SO,is presentin litres of a solution. The molarity of the solutionis
(1) 0.1 M (2) 0.05 M (3) 0.01M (4)0.5 M
50. Molarity of a solution that contains 49 g H.PO,in litres of solution is
(1) 0.25 (2) 0.5 (3) 0.75 (4) 1.0
51. How muchwateris added to 10 ml of 10 N HNO,to make its conc. 0.1 N?
(1) 100 ml (2) 1010 ml (3) 990 ml (4) 1000 ml
52. Whatis the solubility of sucrose sugar, C,,H.,,O,,, at 20°C?

(1) 55g/100 g water (2) 75 g/100 g water

(3) 90 g/100 g water (4) 204 g/100 g water

53. Whatis the mass of a 10.0% bloodplasma solution that contains 2.50 g of dissolved solute?
(1) 0.250 g (2) 0.278 g {3) 25.0 g {4) 250 g
54. Whatis the mass of water needed to prepare 5.00 kg of a 40.0% antifreeze solution?

(1) 2.00 kg (2) 3.00 kg (3) 3.33 kg (4) 12.5 kg

55. Whensalt is dissolved in water, there is

Gh
\ Science Clym piads\Chemistry\02 “Classification of materials. p65
(2) no changein boiling point.

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(1) an increase of boiling point.

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(3) a decrease of boiling point. (4) none of these

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Solubility of deliquescent substances in water generally

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56.

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(1) High ‘ (2) Modulate (3) Low (4) Cannotbe said

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57. Coca-Cola is carbonated by injecting the liquid with carbon dioxide gas. Under what conditionsis the solubility of
carbon dioxide the greatest?
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(1) Low temperature, low pressure (2) Low temperature, high pressure
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(3) Low temperature, pressure is not a factor (4) High pressure, temperature is not a factor
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58. Whichof the followingillustrates thelike dissolveslike rule for two liquids?
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(1) A polarsolvent is insoluble in a polarsolvent.

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(2) A polar solventis soluble in a nonpolar solvent.

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(3) A nonpolar solventis soluble in a nonpolar solvent.

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(4) All of these

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 ALLER Chemistry
59. App! i dissolveslike
Pply the like : rule to predict which ofthe following liquids is miscible with water

(1) chloroform,CHCl, (2) glycerin,C,H,(OH),

_ (8) toluene,C,H,CH, (4) All of the above

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60. Grease spots from garments can be separated by a method of

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(1) chromatography (2) solvent extraction

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(3) sublimation
.
(4) dissolution in suitable solvents
ne

ions formed?
ol. Whensolid potassium fluoride dissolvesin water, which of the followingis one of the aqueous
1.
PIT OTR BEERS ea

(1) Kt-H-O (2) K---0-H (3) F=--O-H (4) all of these

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a solid solute in a solvent?
62. Whichof the following increases the rate of dissolving for
(2) Heating the solution
(1) Grinding the solute
(4) All of these
(3) Stirring the solution
Which is not correctly matched?
emulsion in each of the following.
63. The type of emulsion is mentioned against the
(2) Shampoo: w/o
(1) Milk: o/w
(4) Cold cream: w/o
(3) Butter: w/o
t in milk that makesit stable is
64. The emulsifying agent presen
(4) lactalbumin
(3) casein
(2) maltose
(1) lactose
ls?
65. Which of the followingis Aeroso (4) Butter
(3) Milk
(2) Fog
(1) Alloy
ted by
and water can be separa
66. A mixture of ethanol (4) sublimation
(3) fractional distillation
(2) decantation
(1) filtration
is incorrectly matched?
67. Which ofthe following (4) Pearls-Solid sol
(3) Fog emulsion
(2) Milk-emulsion
(1) Butter-sol stalis
th e so lu ti on in contact with the cry
ion takes place, (4) supersaturated
68. After crystallizat (3) sa turated
(2) unsaturated |
(1) concentrated
rrectl y ma tc he d?
e following is co (4) Solid sol-cake
69. Which one of th (3) Aerosol-smoke
(2) Foam-mist as un “
aon
(1) Em ul si on -c ur d
a co ll oi da l sy stem i s knowno
phase particle in
g- za g mo ve me nt of dispersed )
70. The zi (3) li near motion
on
motion (2) circular moti “ secioplting
(1) transitional |
t takes place in ;
71. Scattering of ligh (3) su sp ension
tions
lu tions (2) colloidal solu ‘parm “ate
(1) el ec tr ol yt ic so iin water:9
solution
llowing forms a colloidal
72. Whichof the fo (3) Starch
e
(2) Glucos |
(1) Salt
an exam le
of
|
(4) suspension
73. Ice cream is | | (3) colloid
on - (2) compound
(1) true soluti
 Class | 4

44. Adsorption property is applied in

(1) sewagedisposal (2) ultramicroscope (3) smoke precipitator (4) medicine

75. Solid foam is

(1) solid dispersed in solid (2) liquid dispersed in solid

(3) gas dispersed in solid (4) solid dispersed in liquid

76. The dispersed phase constitutes

(1) solvent (2) solute (3) solution (4) mixture of solvent

77. Mixture of ZnCl, and PbCl, can be separated by

(1) distillation (2) crystallisation (3) sublimation (4) adding acetic acid

78. The process used to separate oil and water is

(1) distillation (2) sublimation

(3) separating funnel (4) chromatography

79. Which of the following shows ‘Tyndall effect’?

(1) Salt solution (2) Starch solution (3) CuSO,solution (4) NaOHsolution

80. Medicines from blood can be detected and separated by

(1) filtration (2) chromatography (3) sublimation (4) centrifugation

ciences Clamoutad<e\\Chemictes\09-Cla<ciheation of materiale 665