Page 1 Chemical Reactions and Equations Chap 1

CHAPTER 1
Chemical Reactions and Equations

1. INTRODUCTION pointing towards the products.

Chemistry is the branch of science in which we study 2.2 Skeletal Chemical Equation
the composition, properties and transformation of
matter. We observe changes in matter all around us. A chemical equation in which symbols and formulae
These changes are of two types : are used instead of words to show a chemical reaction
is called a skeletal chemical equation.
1.1 Physical Change
2.3 Balanced Chemical Equation
A change in which there is a change in physical
appearance of a substance but no change in its A chemical equation in which the number of atoms of
basic composition, is known as a physical change. each element of reactants is equal to that of products,
For example, melting of butter and wax, boiling of is called a balanced chemical equation.
water, dissolving of salt in water, breaking of glass,
2.4 Balancing a Chemical Equation
sublimation of a solid on heating, etc. No new chemical
substance is formed in a physical change. Equalising the number of atoms of each element on
reactants and products sides of a chemical equation is
1.2 Chemical Change called balancing a chemical equation.
A change in which one or more new substances A chemical equation can be made more informative
having properties and compositions different from the by adding physical states of reactants and products,
original substance are formed, is known as a chemical reaction conditions, heat change during the reaction,
change. For example, burning of paper, wood, coal i.e., heat released or absorbed, concentration of
and magnesium ribbon, making of curd from milk, reactants and products, speed or rate of the reaction,
digestion of food, ripening of fruits, bursting of a i.e., slow or fast, and nature of the reaction, i.e.,
cracker, boiling of egg, etc. Chemical changes are also forward or backward to the equation.
called chemical reactions.
2.5 Characteristics of Chemical Equations
A chemical reaction is accompanied by changes in
physical state, formation of a precipitate, change of 1. Chemical equation gives the names of different
colour, change in temperature or evolution of a gas. reactants and products of a chemical reaction.
Normally, a chemical change is permanent and 2. It gives the number of atoms or molecules of
cannot be reversed easily. reactants and products of a chemical reaction.
3. Chemical equation gives relative number of moles
2. CHEMICAL EQUATION of reactants and products.
4. It gives the relative amount by mass or weight of
2.1 Word Equation reactants and products.
5. Chemical equation also gives relative volume of
A word equation simply shows the change of reactants
gaseous reactants and products.
to products through an arrow placed between them.
The reactants are written on the left-hand side (LHS)
with a plus sign in case of two or more reactants and 3. TYPES OF CHEMICAL REACTIONS
the products are written on the right-hand side (RHS)
with a plus sign in case of two or more products. 3.1 Combination Reaction
The arrowhead shows the direction of the reaction
A reaction in which two or more substances combine
Page 2 Chemical Reactions and Equations Chap 1

together to form a single product is known as a Zn (s) + dil.H2 SO 4 (aq) " ZnSO 4 (aq) + H2 (g) -
combination reaction.
The combination reaction is often called synthesis. 3.4 Double Displacement Reaction
MgO (s) + H2 O (l) Mg (OH) 2 (aq) + Heat
Heat
The reaction in which anions and cations of two
Magnesium oxide Water Magnesium hydroxide
different molecules exchange places, forming two
3.2 Decomposition Reaction completely different compounds is called double
The reaction in which a single substance breaks displacement reaction. For example,
down to form two or more substances, is called a Na2 SO 4 (aq) + BaCl2 (aq) " BaSO 4 (s) . + 2NaCl (aq)
decomposition reaction. For example, decomposition Sodium
sulphate
Barium
chloride
Barium
sulphate
Sodium
chloride

of FeSO 4 on heating.
The common types of double displacement reactions
Fe2 O 3 (s) + SO2 (g) + SO 3 (g)
Heat
2FeSO 4 (s) are as follows:
Ferric oxide

3.3 Displacement Reaction 1. Precipitation Reaction : It is a chemical reaction

in which one of the products is precipitated as an
The reaction in which one atom or a group of atoms insoluble solid. For example,
of a compound is replaced by another atom, is called AgNO 3 (aq) + NaCl (aq) " AgCl (s) . + NaNO 3 (aq)
a displacement reaction. Generally, a more reactive (White ppt.)

metal displaces a less reactive metal from its salt 2. Neutralisation Reaction : It is chemical reaction in
solution in displacement reaction. which a strong acid and a strong base react with
The series in which metals are arranged in the each other to form water and salt. For example,
decreasing order of their reactivity is called activity NaOH (aq) + HCl (aq) " NaCl (aq) + H2 O (l)
series of metals. 3.5 Redox Reaction
Potassium (K) Most reactive 1. Oxidation : If a substance gains oxygen or loses
Sodium (Na) hydrogen in a reaction, the substance is said to be
oxidised and the process is known as oxidation.
Calcium (Ca)
2. Reduction : If a substance loses oxygen and gains
Magnesium (Mg) hydrogen in a reaction, the substance is said to
Aluminium (Al) be reduced and the process involved is known as
reduction.
Zinc (Zn)
Reduction and oxidation take place simultaneously
Iron (Fe) in few reactions. Such reactions are known as
Lead (Pb) redox reactions.
3. Oxidising Agent : If a substance oxidises the other
Copper (Cu)
substance but itself gets reduced, then it is known
Silver (Ag) as an oxidising agent.
Gold (Au) 4. Reducing Agent : If a substance reduces the other
substance but itself gets oxidised, then it is known
Platinum (Pt) Least reactive
as a reducing agent.
Activity series of some common metals For example,
Few examples of displacement reactions are as follows: MgO + H2 $ Mg + H2 O
1. Displacement of copper from a solution of copper Here, H2 is the reducing agent as it reduces MgO
sulphate by iron to Mg and itself gets oxidised to H2 O. On the
Fe (s) + CuSO 4 (aq) " Cu (s) + FeSO 4 (aq) other hand, magnesium oxide is the oxidising
agent which oxidises H2 to H2 O and itself gets
2. Displacement of silver from silver nitrate solution
reduced to Mg.
by copper
Thus, an oxidising agent gets reduced and a
Cu (s) + 2AgNO 3 (aq) " 2Ag (s) + Cu (NO 3) 2 (aq)
reducing agent gets oxidised in a redox reaction.
3. Displacement of iron from iron sulphate solution
by magnesium
Mg (s) + FeSO 4 (aq) " MgSO 4 (aq) + Fe (s)
4. Zinc displaces hydrogen from dilute sulphuric
acid.
Page 3 Chemical Reactions and Equations Chap 1

OBJECTIVE QUESTIONS

1. Which of the statements about the reaction below are

incorrect ?
2PbO (s) + C (s) $ 2Pb (s) + CO2 (g)
(a) Lead is getting reduced.
3.6 Electronic Concept of Oxidation and Reduc- (b) Carbon dioxide is getting oxidised.
tion (c) Carbon is getting oxidised.
Oxidation is the loss of electrons by a species (an (d) Lead oxide is getting reduced.
atom, a molecule or an ion). (i) (a) and (b)
K $ K+ + e- (ii) (a) and (c)
Zn + Zn2+ $ 2e - (iii) (a), (b) and (c)
Reduction is the gain of electrons by a species (an (iv) all
Sol :
atom, a molecule or an ion).
Ag + + e - $ Ag
S + 3e - $ S2- 2. Fe2 O 3 + 2Al $ Al2 O 3 + 2Fe
1. Exothermic Reaction : A chemical reaction in The above reaction is an example of a :
which heat is released along with the formation (a) combination reaction
of product, is called exothermic reaction. For (b) double displacement reaction
example,
(c) decomposition reaction
C (s) + O2 (g) $ CO2 (g) + Heat
(d) displacement reaction.
CaO (s) + H2 O (l) $ Ca (OH) 2 (aq) + Heat Sol :
Calcium oxide Water Calcium hydroxide
(Lime) (Slaked lim e)

2. Endothermic Reaction : A chemical reaction in

3. What happens when dilute hydrochloric acid is added
which heat is absorbed along with the formation
to iron fillings? Tick the correct answer :
of product, is called endothermic reaction. For
example, (a) Hydrogen gas and iron chloride are produced.
NH 4 Cl (s) + H2 O (l) $ NH 4 Cl (aq) - Heat (b) Chlorine gas and iron hydroxide are produced.
N2 (g) + O2 (g) $ 2NO (g) - Heat (c) No reaction takes place.

3.7 Corrosion (d) Iron salt and water are produced.

Sol :
It is the process of slow conversion of metals into their
undesirable compounds by the attack of air (oxygen) 1. Which of the following is not a physical change ?
and moisture.
(a) Boiling of water to give water vapour
1. Rusting : When iron and iron articles are exposed
to air and water, a reddish-brown layer is formed (b) Melting of ice to give water
on the surface. This layer is called rust [hydrated (c) Dissolution of salt in water
iron(III) oxide, Fe2 O 3 $ x H2 O ]. Hence, corrosion (d) Combustion of liquefied petroleum gas (LPG)
of iron is known as rusting. Sol :
2. Rancidity : When cooked food items containing
oil and fat are kept exposed and unprotected, 2. The following reaction is an example of a :
they become rancid and produce an unpleasant
4NH 3 (g) + 5O2 (g) $ 4NO (g) + 6H2 O (g)
smell and taste. The phenomenon involved here is
known as rancidity. (i) displacement reaction
3. Prevention of Rancidity : Rancidity can be (ii) combination reaction
prevented by adding antioxidants, keeping food (iii) redox reaction
items at low temperature, keeping food items (iv) neutralization reaction
in vacuum packing or airtight container and (a) (i) and (iv) (b) (ii) and (iii)
replacing air by nitrogen gas.
Page 4 Chemical Reactions and Equations Chap 1

(c) (i) and (iii) (d) (iii) and (iv) (b) FeSO 4 acts as an oxidising agent and oxidises
Sol : KMnO 4
(c) The colour disappears due to dilution; no reaction
3. Which of the following statements about the given is involved
reaction are correct ?
(d) KMnO 4 is an unstable compound and decomposes
3Fe (s) + 4H2 O (g) $ Fe 3 O 4 (s) + 4H2 (g) in presence of FeSO 4 to a colourless compound.
(i) Iron metal is getting oxidised Sol :
(ii) Water is getting reduced
(iii) Water is acting as reducing agent 7. Which among the following is(are) double displacement
(iv) Water is acting as oxidising agent. reaction(s) ?
(a) (i), (ii) and (iii) (b) (iii) and (iv) (i) Pb + CuCl2 $ PbCl2 + Cu
(c) (i), (ii) and (iv) (d) (ii) and (iv) (ii) Na2 SO 4 + BaCl2 $ BaSO 4 + 2NaCl
Sol : (iii) C + O2 $ CO2
(iv) CH2 + 2O2 $ CO2 + 2H2 O
4. Three beakers labelled as A, B and C each containing (a) (i) and (iv) (b) (ii) only
25 mL of water were taken. A small amount of (c) (i) and (ii) (d) (iii) and (iv)
NaOH, anhydrous CuSO 4 and NaCl were added to Sol :
the beakers A, B and C respectively. It was observed
that there was an increase in the temperature of the
8. Which among the following statement(s) is(are) true?
solutions contained in beakers A and B, whereas in
Exposure of silver chloride to sunlight for a long
case of beaker C, the temperature of the solution
duration turns grey due to :
falls. Which one of the following statement(s) is(are)
correct ? (i) the formation of silver by decomposition of silver
chloride
(i) In beakers A and B, exothermic process has
occurred. (ii) sublimation of silver chloride
(ii) In beakers A and B, endothermic process has (iii) decomposition of chlorine gas from silver chloride
occurred. (iv) oxidation of silver chloride
(iii) In beaker C exothermic process has occurred. (a) (i) only (b) (i) and (iii)
(iv) In beaker C endothermic process has occurred. (c) (ii) and (iii) (d) (iv) only
Sol :
(a) (i) only (b) (ii) only
(c) (i) and (iv) (d) (ii) and (iii)
Sol : 9. Solid calcium oxide reacts vigorously with water to
form calcium hydroxide accompanied by liberation of
heat. This process is called slaking of lime. Calcium
5. Which of the following are exothermic processes ?
hydroxide dissolves in water to form its solution called
(i) Reaction of water with quicklime lime water. Which among the following is (are) true
(ii) Dilution of an acid about slaking of lime and the solution formed ?
(iii) Evaporation of water (i) It is an endothermic reaction
(iv) Sublimation of camphor (crystals) (ii) It is an exothermic reaction
(a) (i) and (ii) (b) (ii) and (iii) (iii) The pH of the resulting solution will be more
(c) (i) and (iv) (d) (iii) and (iv) than seven
Sol : (iv) The pH of the resulting solution will be less than
seven
6. A dilute ferrous sulphate solution was gradually added (a) (i) and (ii) (b) (ii) and (iii)
to the beaker containing acidified permanganate (c) (i) and (iv) (d) (iii) and (iv)
solution. The light purple colour of the solution fades Sol :
and finally disappears. Which of the following is the
correct explanation for the observation ?
10. Barium chloride on reacting with ammonium sulphate
(a) KMnO 4 is an oxidising agent, it oxidises FeSO 4 forms barium sulphate and ammonium chloride.
Page 5 Chemical Reactions and Equations Chap 1

Which of the following correctly represents the type 15. The following reaction is used for the preparation of
of the reaction involved ? oxygen gas in the laboratory
2KClO 3 (s) Catalyst 2KCl (s) + 3O2 (g)
Heat
(i) Displacement reaction
(ii) Precipitation reaction Which of the following statement(s) is(are) correct
(iii) Combination reaction about the reaction?
(iv) Double displacement reaction (a) It is a decomposition reaction and endothermic in
(a) (i) only (b) (ii) only nature.
(c) (iv) only (d) (ii) and (iv) (b) It is a combination reaction.
Sol : (c) It is a decomposition reaction accompanied by
release of heat.
11. Electrolysis of water is a decomposition reaction. The (d) It is a photochemical decomposition reaction and
mole ratio of hydrogen and oxygen gases liberated exothermic in nature.
during electrolysis of water is : Sol :
(a) 1 : 1 (b) 2 : 1
(c) 4 : 1 (d) 1 : 2 16. Which one of the following processes involve chemical
Sol : reactions ?
(a) Storing of oxygen gas under pressure yiri a gas
For solutions download NODIA app. cylinder
(b) Liquefaction of air
12. Which of the following is(are) an endothermic
process(es) ? (c) Keeping petrol in a china dish in the open
(i) Dilution of sulphuric acid (d) Heating copper wire in presence of air at high
(ii) Sublimation of dry ice temperature
Sol :
(iii) Condensation of water vapours
(iv) Evaporation of water
17. In which of the following chemical equations,
(a) (i) only (iii) (b) (ii) only
the abbreviations represent the correct states of
(c) (iii) only (d) (ii) and (iv) the reactants and products involved at reaction
Sol : temperature ?
(a) 2H2 (l) + O2 (l) $ 2H2 O (g)
13. In the double displacement reaction between aqueous (b) 2H2 (g) + O2 (l) $ 2H2 O (l)
potassium iodide and aqueous lead nitrate, a yellow
precipitate of lead iodide is formed. While performing (c) 2H2 (g) + O2 (g) $ 2H2 O (l)
the activity if lead nitrate is not available, which of (d) 2H2 (g) + O2 (g) $ 2H2 O (g)
the following can be used in place of lead nitrate ? Sol :
(a) Lead sulphate (insoluble)
(b) Lead acetate 18. Which of the following are combination reactions?
2KCl + 3O2
Heat
(i) 2KClO 3
(c) Ammonium nitrate
(ii) MgO + H2 O $ Mg (OH) 2
(d) Potassium sulphate
Sol : (iii) 4Al + 3O2 $ 2Al2 O 3
(iv) Zn + FeSO 4 $ ZnSO 4 + Fe
14. Which of the following gases can be used for storage (a) (i) and (iii) (b) (iii) and (iv)
of fresh sample of an oil for a long time ? (c) (ii) and (iv) (d) (ii) and (iii)
Sol :
(a) Carbon dioxide or oxygen
(b) Nitrogen or oxygen
19. A solution of potassium chloride when mixed with
(c) Carbon dioxide or helium silver nitrate solution, an insoluble white substance is
(d) Helium or nitrogen formed. Write the chemical reaction involved and also
Sol : mention the type of the chemical reaction ?
Sol :
Page 6 Chemical Reactions and Equations Chap 1

20. Ferrous sulphate decomposes with the evolution of a Column I Column II

gas having a characteristic odour of burning sulphur.
Write the chemical reaction involved and identify the (D) C 2 H 6 T
(s) ZnO
type of reaction.
Sol :
A B C D

21. Why do fire flies glow at night ? (a) p s, r q, r q, r

Sol :
(b) p q, r s, r r, p
(c) q,r s,p p, s r
22. Grapes hanging on the plant do not ferment but
after being plucked from the plant can be fermented. (d) r q s p
Under what conditions do these grapes ferment ? Is it Sol :
a chemical or a physical change ?
Sol :
26. Assertion : Corrosion of iron is a serious problem.
Reason : Every year an enormous amount of money is
23. Which among the following are physical or chemical spent to replace damaged iron.
changes ? (a) Both Assertion and Reason are True and Reason
(a) Evaporation of petrol is the correct explanation of the Assertion.
(b) Burning of Liquefied Petroleum Gas (LPG) (b) Both Assertion and Reason are True but Reason
(c) Heating of an iron rod to red hot. is not the Correct explanation of the Assertion.
(d) Curdling of milk.
(c) Assertion is True but the Reason is False.
(e) Sublimation of solid ammonium chloride
Sol : (d) Both Assertion and Reason are False.
Sol :

24. Match the column I to column II and select the correct

answer using the codes given below: 27. Assertion : Changing of colour of copper from reddish
brown to black is an example of reduction.
Column I Column II Reason : Hydrogen is removed.
(A) C + O 2 " CO 2 (p) Displacement (a) Both Assertion and Reason are True and Reason
is the correct explanation of the Assertion.
(B) AgBr
light
Ag + Br (q) Combination
(b) Both Assertion and Reason are True but Reason
(C) Zn + CuSO 4 " ZnSO 4 + Cu (r) Decomposition is not the Correct explanation of the Assertion.
(D) CH 3 CH 2 OH
Cu
CH 3 CHO + H 2 (s) Oxidation (c) Assertion is True but the Reason is False.
(d) Both Assertion and Reason are False.
A B C D Sol :

(a) q r p s
28. Assertion : When iron nail is dipped in copper sulphate
(b) p q, s, r,
solution, the iron nail becomes brownish in colour and
(c) r s, p, q the blue colour of copper solution fade.
(d) r q s p Reason : Equation representing this change is
Sol : Cu + FeSO 4 $ CuSO 4 + Fe
(a) Both Assertion and Reason are True and Reason
25. Column II gives type of reaction mention in column I, is the correct explanation of the Assertion.
match them correctly. (b) Both Assertion and Reason are True but Reason
is not the Correct explanation of the Assertion.
Column I Column II
(c) Assertion is True but the Reason is False.
(A) KClO 3 T
(p) O 2
(d) Both Assertion and Reason are False.
(B) ZnCO 3 T
(q) H 2 O Sol :

(C) H 2 CO 3 T
(r) CO 2
Page 7 Chemical Reactions and Equations Chap 1

29. Assertion : Silver chloride turns grey is sunlight. reaction.

Reason : Silver is one of the least reactive metals. Reason : In the given above equation, carbon and
(a) Both Assertion and Reason are True and Reason oxygen react to give carbon dioxide.
is the correct explanation of the Assertion. (a) Both Assertion and Reason are True and Reason
(b) Both Assertion and Reason are True but Reason is the correct explanation of the Assertion.
is not the Correct explanation of the Assertion. (b) Both Assertion and Reason are True but Reason
(c) Assertion is True but the Reason is False. is not the Correct explanation of the Assertion.

(d) Both Assertion and Reason are False. (c) Assertion is True but the Reason is False.
Sol : (d) Both Assertion and Reason are False.
Sol :
30. Assertion : When water is added to calcium oxide, a
large amount of heat is produced. 34. Assertion : Chips manufacturers usually flush bags of
Reason : It is an endothermic reaction. chips with oxygen gas.
(a) Both Assertion and Reason are True and Reason Reason : It adds taste to chips.
is the correct explanation of the Assertion. (a) Both Assertion and Reason are True and Reason
(b) Both Assertion and Reason are True but Reason is the correct explanation of the Assertion.
is not the Correct explanation of the Assertion. (b) Both Assertion and Reason are True but Reason
(c) Assertion is True but the Reason is False. is not the Correct explanation of the Assertion.

(d) Both Assertion and Reason are False. (c) Assertion is True but the Reason is False.
Sol : (d) Both Assertion and Reason are False.
Sol :
31. Assertion : A chemical equation should be balanced.
Reason : Number of atoms of each element should be 35. Assertion : Precipitation reactions produce insoluble
same on reactants as well as products side. salts.
(a) Both Assertion and Reason are True and Reason Reason : Precipitation reaction is a double
is the correct explanation of the Assertion. decomposition reaction.
(b) Both Assertion and Reason are True but Reason (a) Both Assertion and Reason are True and Reason
is not the Correct explanation of the Assertion. is the correct explanation of the Assertion.

(c) Assertion is True but the Reason is False. (b) Both Assertion and Reason are True but Reason
is not the Correct explanation of the Assertion.
(d) Both Assertion and Reason are False.
Sol : (c) Assertion is True but the Reason is False.
(d) Both Assertion and Reason are False.
Sol :
32. Assertion : Chemical equations can be made more
informative.
For solutions download NODIA app.
Reason : We can write physical state of reactants and
products, temperature and pressure, name of catalyst
used etc. 36. Assertion : During digestion, carbohydrates are
broken down to form glucose.
(a) Both Assertion and Reason are True and Reason
is the correct explanation of the Assertion. Reason : Glucose is necessary for breathing.
(a) Both Assertion and Reason are True and Reason
(b) Both Assertion and Reason are True but Reason
is the correct explanation of the Assertion.
is not the Correct explanation of the Assertion.
(b) Both Assertion and Reason are True but Reason
(c) Assertion is True but the Reason is False.
is not the Correct explanation of the Assertion.
(d) Both Assertion and Reason are False.
Sol : (c) Assertion is True but the Reason is False.
(d) Both Assertion and Reason are False.
Sol :
33. Assertion : Equation
C (s) + O2 (g) $ CO2 (g) is an example of combination
Page 8 Chemical Reactions and Equations Chap 1

37. Assertion : Decomposition reactions are similar to 41. Assertion : Carbon dioxide turns lime water milky.
combination reactions. Reason : Carbon dioxide sullies the water.
Reason : Both reactions need a catalyst to occur. (a) Both Assertion and Reason are True and Reason
(a) Both Assertion and Reason are True and Reason is the correct explanation of the Assertion.
is the correct explanation of the Assertion. (b) Both Assertion and Reason are True but Reason
(b) Both Assertion and Reason are True but Reason is not the Correct explanation of the Assertion.
is not the Correct explanation of the Assertion. (c) Assertion is True but the Reason is False.
(c) Assertion is True but the Reason is False. (d) Both Assertion and Reason are False.
(d) Both Assertion and Reason are False. Sol :
Sol :
42. Assertion : A chemical reaction becomes faster at
38. Assertion : Corrosion of iron is commonly known as higher temperatures.
rusting. Reason : At higher temperatures, molecular motion
Reason : Corrosion of iron occurs in presence of water becomes more rapid.
and air. (a) Both Assertion and Reason are True and Reason
(a) Both Assertion and Reason are True and Reason is the correct explanation of the Assertion.
is the correct explanation of the Assertion. (b) Both Assertion and Reason are True but Reason
(b) Both Assertion and Reason are True but Reason is not the Correct explanation of the Assertion.
is not the Correct explanation of the Assertion. (c) Assertion is True but the Reason is False.
(c) Assertion is True but the Reason is False. (d) Both Assertion and Reason are False.
(d) Both Assertion and Reason are False. Sol :
Sol :
43. Assertion : The following chemical equation,
39. Assertion : A reducing agent is a substance which can 2C6 H6 + 7O2 $ 4CO2 + 6H2 O
either accept electron.
Reason : A substance which helps in oxidation is is a balanced chemical equation.
known as reducing agent. Reason : In a balanced chemical equation, the total
(a) Both Assertion and Reason are True and Reason number of atoms of each element may or may not
is the correct explanation of the Assertion. equal on both side of the equation.
(a) Both Assertion and Reason are True and Reason
(b) Both Assertion and Reason are True but Reason
is the correct explanation of the Assertion.
is not the Correct explanation of the Assertion.
(b) Both Assertion and Reason are True but Reason
(c) Assertion is True but the Reason is False.
is not the Correct explanation of the Assertion.
(d) Assertion (A) is false but reason (R) is true.
Sol : (c) Assertion is True but the Reason is False.
(d) Both Assertion and Reason are False.
40. Assertion : The balancing of chemical equations is
based on law of conservation of mass. 44. Assertion : Fe2 O 3 + 2Al $ Al2 O 3 + 2Fe
Reason : Total mass of reactants is equal to total mass The above chemical equation is an example of
of products. displacement reaction.
(a) Both Assertion and Reason are True and Reason Reason : Aluminium being more reactive than iron,
is the correct explanation of the Assertion. displaces Fe from its oxide.
(b) Both Assertion and Reason are True but Reason (a) Both Assertion and Reason are True and Reason
is not the Correct explanation of the Assertion. is the correct explanation of the Assertion.
(c) Assertion is True but the Reason is False. (b) Both Assertion and Reason are True but Reason
is not the Correct explanation of the Assertion.
(d) Both Assertion and Reason are False.
Sol : (c) Assertion is True but the Reason is False.
(d) Both Assertion and Reason are False.
Sol :
Page 9 Chemical Reactions and Equations Chap 1

45. Assertion : Photosynthesis is considered as an 51. Hydrogen and oxygen combine with each other to
endothermic reaction. form water. Name the reactants and products.
Sol : Comp 2014
Reason : Energy gets released in the process of
photosynthesis.
(a) Both Assertion and Reason are True and Reason 52. The molecular formula of chloride of cation X is
is the correct explanation of the Assertion. XCl. What is the formula of nitrate of X ?
Sol : OD 2011

(b) Both Assertion and Reason are True but Reason

is not the Correct explanation of the Assertion.
53. Give the values of x, y, z for the equation :
(c) Assertion is True but the Reason is False. x HCl + O2 $ y H2 O + z Cl2
Sol : Foreign 2009
(d) Both Assertion and Reason are False.
Sol :
54. What is meant by skeletal equation ?
Sol : OD 2018
46. Assertion : In the following chemical equation,
CuO (s) + Zn (s) $ ZnO (s) + Cu (s)
55. Write a balanced chemical equation to represent the
Zinc is getting oxidised and copper oxide is getting
following reaction :
reduced.
Carbon monoxide reacts with hydrogen gas at 340
Reason : The process in which oxygen is added to a
atm. to form methyl alcohol.
substance is called oxidation whereas the process in Sol : Foreign 2016
which oxygen is removed from a substance is called
reduction.
56. Complete and balance the following reaction :
(a) Both Assertion and Reason are True and Reason
Fe2 O 3 + Al $
is the correct explanation of the Assertion. Sol : OD 2007

(b) Both Assertion and Reason are True but Reason

is not the Correct explanation of the Assertion. 57. Balance the chemical equation:
(c) Assertion is True but the Reason is False. Pb (NO 3) 2 (s)
Heat
PbO (s) + NO2 (g) + O2 (g)
Sol : Delhi 2010
(d) Both Assertion and Reason are False.
Sol :
58. Balance the following chemical equation :
Fe2 O 3 (s) + SO2 (g) + SO 3 (g)
Heat
FeSO 4 (s)
Sol : Comp 2019

ONE MARK QUESTIONS

59. Name the type of the following reaction :
Fe + S $ FeS .
Sol : Foreign 2006
47. What is a balanced chemical equation ?
or
60. Name the reaction in which two substances react to
Define a balanced chemical equation.
Sol : Comp 2021, 16 form a new substance.
Sol : OD 2013

48. Name the type of chemical reaction which takes place

61. What type of reaction occurs in the digestion of food
when quicklime is added to water.
Sol : Comp 2021 in our body ?
Sol : Delhi 2009

49. Which one is a chemical change fermentation of fruit

62. Which of the following represents an exothermic
juice or diluting fruit juice ?
Sol : Foreign 2010 reaction ?
CaO + CO2
Heat
(i) CaCO 3
50. Which one is a chemical change rusting of iron or (ii) C + O2 $ CO2 + Heat
Sol : OD 2014
melting of iron ?
Sol : Delhi 2017
Page 10 Chemical Reactions and Equations Chap 1

63. What is the reaction called in which an element, 75. What is the brown coloured gas evolved when lead
molecule or ion is removed by another ? nitrate crystals are heated in a dry test tube ?
Sol : Foreign 2017 Sol : Delhi 2013

64. Name the type of reaction involved in the following : 76. Give an example of an endothermic reaction.
Sol : OD 2015
CuSO 4 + Zn $ ZnSO 4 + Cu
Sol : OD 2006

77. When magnesium. ribbon burns in the air and forms a

65. Identify the component oxidised in the following white ash, is magnesium oxidised or reduced ?
Sol : Foreign 2010
reaction :
CuO + H2 $ Cu + H2 O
Sol : Delhi 2013 78. In the following reaction identify which one is reduced
and which one is oxidised ?
66. What is the reaction in which one substance is oxidised MnO2 + 4HCl $ MnCl2 + 2H2 O + Cl2
Sol : Delhi 2012
and the other is reduced called ?
Sol : Foreign 2012

79. Identify the substance that is oxidised and reduced in

67. Name the reaction in which oxygen is removed from the reaction :
a substance. CuO (s) + Zn (s) $ Cu (s) + ZnO (s)
Sol : Comp 2020 Sol : Comp 2017

68. Name the reaction in which oxygen is added to a 80. Name two effects of oxidation in daily life.
Sol : OD 2012
substance.
Sol : OD 2007

81. Why do iron articles become brown after some time ?

Sol : Delhi 2006
69. Arrange iron, zinc and copper in the order of their
increasing reactivity.
Sol : Comp 2011
82. Name two metals which are corrodised.
Sol : OD 2009

70. Give an example of an exothermic reaction.

Sol : CBSE 2010
83. Why do the colour and taste of fats and oils change
after sometimes ?
Sol : Comp 2012
71. White silver chloride turns grey in sunlight. Why ?
Sol : OD 2015

84. Write two conditions of corrosion.

Sol : OD 2018
72. Name the type of reaction in N2 + 3H2 $ 2NH 3 .
Sol : Comp 2018

85. Why are bags of chips flushed with nitrogen gas ?

73. What changes do you observe in the iron nails and or
colour of copper sulphate solution if the iron nails are Potato chips manufactures fill the packet of chips with
dipped in CuSO 4 solution for 15 minutes ? nitrogen gas. Why ?
or Sol : CBSE 2010, 16

What happens when an iron nail is put inside copper

sulphate solution ? Write reaction with observation. 86. Why do silver ornaments lose their shine when kept
Sol : Delhi 2007
for some time ?
Sol : Delhi 2019

74. Give an example of a double displacement reaction

(only reaction with complete balanced equation). 87. Name the gas that can be used for storage of fresh
Sol : Comp 2009
sample of chips for a long time.
Sol : Comp 2007
For solutions download NODIA app.
Page 11 Chemical Reactions and Equations Chap 1

88. Complete the missing component/variable given as 100. Write the balanced equation for the following reaction
X and Y in the following reaction : and identify the type of reaction :
Zn (s) + H2 SO 4 (aq) $ ZnSO 4 (X ) + H2 (Y )
T
Potassium chlorate(s) Potassium chloride(s) +
Sol : Foreign 2012
Oxygen(g)
Sol : OD 2010

89. Name the reducing agent in the following reaction :

2MnO2 + 4Al $ 3Mn + 2Al2 O 3 101. Tell whether respiration is exothermic reaction or
Sol : Delhi 2014
endothermic reaction. Why ?
Sol : Comp 2011

90. A silver spoon is kept immersed in an aqueous solution

of copper sulphate. What change would be observed 102. What do you mean when we say that a substance has
in the spoon as well as in the solution ? gone rancid ?
Sol : Comp 2012 Sol : SQP 2006

91. Balance the following chemical equation : 103. Identify the type of chemical reaction and write
Fe (s) + H2 O (g) $ Fe 3 O 4 (s) + H2 (g) balanced chemical equation for the following :
Sol : OD 2009
On heating copper powder in a china dish, the surface
of copper powder becomes black.
Sol : Foreign 2010
92. Identify the type of reaction in the chemical equation
given below :
Na2 SO 4 (aq) + BaCl2 (aq) $ 2NaCl (aq) + BaSO 4 (s) 104. Identify the type of chemical reaction and write the
Sol : OD 2013 balanced chemical equation for the following :
Quicklime reacts vigorously with water releasing a
93. Give one example of the decomposition reaction. large amount of heat.
Sol : OD 2012
Write the balanced chemical equation which occurs on
passing electric current. Write the balanced chemical
equation. 105. State reason for the following : Iron articles loose their
Sol : Delhi 2009
shine gradually.
Sol : Foreign 2015

94. Write one equation for decomposition reaction which

occurs in the presence of light. 106. What are antioxidants ? Why are they added to fat
Sol : Foreign 2012
and oil containing foods ?
Sol : Delhi 2013

95. Write one equation for decomposition reaction which

occurs in the presence of heat. 107. Define redox reaction.
Sol : SQP 2016 Sol : SQP 2008

96. State one industrial application of reduction process. 108. Write the balanced chemical equation for the following
Sol : SQP 2008
reaction :
Aluminium + Copper chloride $ Aluminium
97. What can be seen when a strip of copper metal is chloride + Copper.
Sol : Comp 2009
placed in a solution of silver nitrate ?
Sol : OD 2006

109. Express the following facts in the form of a balanced

98. State the type of chemical reaction with chemical chemical equation :
equation which takes place in the following : Barium chloride solution reacts with sodium sulphate
Magnesium wire burnt in air. solution to give insoluble barium sodium sulphate and
Sol : Foreign 2014
a solution of chloride.
Sol : Delhi 2008

99. Define the term decomposition reaction.

Sol : Delhi 2011 For solutions download NODIA app.
Page 12 Chemical Reactions and Equations Chap 1

TWO MARKS QUESTIONS (ii) Na + H+ $ Na+ + H2

(iii) Sn2+ + Hg2+ $ Sn 4+ + Hg+
(iv) Fe + H+ $ Fe2+ + H2
110. Give the chemical name of the ractants as well as the Sol : Foreign 2017

products of the following chemical eqauation :

HNO 3 + Ca (OH) 2 $ Ca (NO 3) 2 + H2 O 119. Translate the following statements into chemical
Sol : Comp 2021
equations and then balance them :
(i) Calcium disulphide burns in air to give carbon
111. What is a chemical equation ? Illustrate with an dioxide and sulphur dioxide.
example. (ii) Sodium metal reacts with water to give sodium
Sol : SQP 2018
hydroxide and hydrogen gas.
(iii) Aluminium metal replaces hydrogen from
112. Change the following reactions into balanced chemical sulphuric acid and gives aluminium sulphate.
equations.
(iv) Ferric oxide oxidises CO to CO2 and itself gets
(i) Manganese dioxide is heated with aluminium reduced to Fe.
powder. Sol : Comp 2013

(ii) Iron is treated with steam.

Sol : OD 2015
120. A magnesium ribbon is burnt in oxygen to give a white
compound ‘ X ’ accompanied by emission of light.
113. What do you understand by skeletal and balanced (a) Write the chemical formula of ‘ X ’.
chemical equation ?
Sol : Foreign 2010 (b) Write a balanced chemical equation, when ‘ X ’ is
dissolved in water.
Sol : OD 2008

114. What are the essentials of a chemical equation?

Sol : OD 2019
121. Explain electrolytic decomposition with suitable
examples.
115. (i) Rewrite the following equation in a balanced Sol : Delhi 2013

form:
Fe + O2 $ Fe2 O 3
122. When ferrous sulphate is heated, the green colour
(ii) Rewrite the following equation indicating that a of ferrous sulphate changes to brown due to the
solution of lime in water has been used and that formation of ferric oxide, with a smell of burning
a precipitate is formed in the reaction. sulphur. Explain the reaction.
Ca (OH) 2 + CO2 $ CaCO 3 + H2 O Sol : Foreign 2015
Sol : Delhi 2006

123. Consider the following displacement reactions :

116. Write the balanced chemical equation for the following
(i) CuSO 4 (aq) + Fe (s) $ FeSO 4 (aq) + Cu (s)
reaction and write the name of the reaction :
(ii) FeSO 4 (aq) + Zn (s) $ ZnSO 4 (aq) + Fe (s)
Barium chloride + Aluminium sulphate " Barium
sulphate + Aluminium chloride State which is the most reactive and which is the least
Sol : SQP 2009 reactive metal out of zinc, copper and iron.
Sol : Delhi 2007

117. Write balanced chemical equations to represent the

following statements : 124. Below are given two chemical reactions. Which one is
a combination reaction and which is a displacement
(i) Carbon (coke) burns in air to form carbon dioxide
reaction ?
gas.
(i) 2KBr (aq) + Cl2 (aq) $ 2KCl (aq) + Br2 (aq)
(ii) A piece of sodium metal on putting in water forms
caustic soda and hydrogen gas. (ii) Fe (s) + S (s) $ FeS (s)
Sol : Comp 2020
Sol : SQP 2009

For solutions download NODIA app.

118. Complete and balance the following ionic equations :
(i) Cu + Ag+ $ Cu2+ + Ag
Page 13 Chemical Reactions and Equations Chap 1

125. What are oxidation reactions ? 132. What is meant by thermal decomposition reaction ?
Sol : Foreign 2011
Explain with an example.
Sol : OD 2013

126. Classify the following on the basis of type of chemical

change : 133. An aluminium can is used to store ferrous sulphate
(i) C + O2 $ CO2 solution. It is observed that in few days holes appeared
(ii) CaCO 3 $ CaO + CO2 in the can. Explain the observation and write chemical
equation to support your answer.
(iii) H2 S + Cl2 $ 2HCl + S Sol : Comp 2015

(iv) NaBr + AgNO 3 $ AgBr + NaNO 3

Sol : SQP 2015
134. Aqueous solutions of lead nitrate and potassium iodide
are mixed together. What change in colour will you
127. “Oxidation and reduction processes occur
observe? Write a balanced equation for the reaction
simultaneously.” Justify this statement with the help
and the type of reaction.
of an example. Sol : OD 2010
Sol : OD 2012

135. What would you observe when zinc is added to a

128. “Barium chloride reacts with aluminium sulphate to
solution of iron (II) sulphate. Name the type of
give aluminium chloride and a precipitate of barium
reaction and write the chemical equation.
sulphate.” Sol : Delhi 2007

(i) Translate the above statement into a chemical

equation. 136. A small amount of ferrous sulphate is heated in a hard
(ii) State two types in which this reaction can be glass test tube.
classified. (i) Write the equations involved in the above reaction.
Sol : Delhi 2014
(ii) What type of reaction is taking place ?
Sol : Delhi 2013

129. Why do we store silver chloride in dark coloured

bottles ? Explain in brief.
Sol : OD 2016 137. What is a redox reaction ? Write down a chemical
equation representing it.
Sol : Comp 2016

130. (i) Define photochemical reaction.

(ii) Write the balanced equation for the following 138. Define combination reaction. Give one example of a
reaction and identify the type of reaction : combination reaction which is also exothermic.
Potassium bromide + Barium iodide " Potassium Sol : SQP 2009, 12

iodide + Barium bromide.

Sol : Comp 2010
139. A white solid when dropped in water produces a hissing
sound. What the solid may be ? Give the chemical
131. “A solution of potassium chloride when mixed with reaction for above. Name the product formed.
silver nitrate solution, an insoluble white substance Sol : Foreign 2013, 11

is formed.”
(i) Translate the above statement into a chemical 140. Name two salts that are used in black and white
equation. photography. Give reactions when they are exposed
(ii) State two types for this reaction. to light.
Sol : Delhi 2006
or
A solution of potassium chloride when mixed with
silver nitrate solution, an insoluble white substance is 141. When the powder of a common metal is heated in
formed. Write the chemical reaction involved and also an open china dish, its colour turns black. However,
mention the type of the chemical reaction. when hydrogen is passed over the hot black substance
Sol : Foreign 2008 so formed, it regains its original colour. Based on the
above information answer the following questions :
For solutions download NODIA app. (i) What type of chemical reaction takes place in
each of the two given steps ?
Page 14 Chemical Reactions and Equations Chap 1

(ii) Name the metal initially taken in the powder taken out of the solution, a number of small holes
form. Write balanced chemical equations for both were noticed in it. State the reason and write chemical
the reactions. equation of the reaction.
Sol : Comp 2009 Sol : SQP 2016

142. What happens when a strip of zinc is dipped into 150. On adding dilute HCl to copper oxide powder, the
copper sulphate solution ? Write the balanced solution formed is blue-green. Predict the new
chemical equation of the reaction. compound which imparts a blue-green colour to the
Sol : OD 2010
solution.
Sol : Delhi 2011, 07

143. Define double displacement reaction with the help of

an example. 151. Identify the substance oxidised, substance reduced,
Sol : Delhi 2008
oxidising agent and reducing agent.
MnO2 + 4HCl $ MnCl2 + 2H2 O + Cl2
144. Identify the substance oxidised and the substance Sol : Foreign 2014, OD 2012

reduced in the following reactions :

(i) MnO2 + 4HCl $ MnCl2 + 2H2 O + Cl2 152. Aluminium is a reactive metal but is still used for
(ii) CuO + H2 $ Cu + H2 O packing food articles. Why ?
Sol : SQP 2012 Sol : Delhi 2015

145. In the electrolysis of water; 153. When a green iron salt is heated strongly, the colour
(i) Name the gases collected at the cathode and the finally changes to black and odour of burning sulphur
anode. is given out.
(ii) Why is a few drops of dil. H2 SO 4 added to the (a) Name the iron salt.
water ? (b) Name the type of reaction that takes place during
Sol : Foreign 2014
the heating of iron salt.
Sol : OD 2010

146. (a) Why is combustion reaction an oxidation reaction?

(b) How will you test whether the gas evolved in a 154. State the kind of chemical reactions in the following
reaction is hydrogen? samples :
Sol : Comp 2017
(a) Digestion of food in stomach.
(b) Combination of coal in air.
Sol : Comp 2007
147. Name the reducing agent in the following reaction :
3MnO2 + 4Al $ 3Mn + 2Al2 O 3
State which is more reactive, Mn or Al and why ? 155. When hydrogen gas burns in presence of oxygen,
Sol : Delhi 2013 water is formed and when water is electrolysed then
hydrogen and oxygen gases are produced. State the
148. Classify the following as exothermic and endothermic kind of reaction that takes place.
reactions : (a) in the first case
(a) Photosynthesis (b) in the second case.
Sol : Delhi 2009
(b) Respiration
(c) Burning of natural gas
156. Give one example of a redox reaction which is also a
(d) Electrolysis of water
Sol : OD 2011 displacement reaction.
Sol : Delhi 2017

For solutions download NODIA app.

157. Which two observations will be made when quicklime
is added to water ?
149. A thin zinc plate was kept in a glass container having Sol : Comp 2006
CuSO 4 solution. On examining it was found that
the blue colour of the solution is getting lighter and For solutions download NODIA app.
lighter. After a few days when the zinc plate was
Page 15 Chemical Reactions and Equations Chap 1

158. What is observed when carbon dioxide gas is passed 166. Identify the type of each of the following reactions.
through lime water : Also write balanced chemical equation for each.
(i) For a short duration. (i) The reaction mixture becomes warm.
(ii) For a long duration. (ii) An insoluble substance is formed.
Sol : Foreign 2016 Sol : Delhi 2012

159. State what happens when zinc granules heated 167. Write a balanced chemical equation to show the
with sodium hydroxide solution. Write the balanced chemical change that occurs when magnesium ribbon
chemical equation for the reaction. Name the main is burnt in air. Name the product formed and mention
product formed in this reduction. the characteristics of the flame produced.
Sol : OD 2011 Sol : Delhi 2016

160. When potassium iodide solution is added to a solution 168. Express the following facts in the form of a balanced
of lead(II) nitrate in a test tube, a precipitate is chemical equation :
formed. (i) When a strip of copper metal is placed in a solution
(i) State the colour of this precipitate. of silver nitrate, metallic silver is precipitated and
(ii) Name the compound precipitated. a solution containing copper nitrate is formed.
(iii) Write the balanced chemical equation for this (ii) Barium chloride solution reacts with sodium
reaction. sulphate solution to give insoluble barium
Sol : SQP 2015, Comp 2013
sulphate and a solution of sodium chloride.
Sol : OD 2010

161. What is a combination reaction ? State one example

giving balanced chemical equation for the reaction. 169. Define a chemical equation. What is an unbalanced
Sol : Foreign 2016, 09
equation called ? What law covers the balancing of a
chemical equation ? State it.
Sol : Comp 2013
162. Select (i) Combination reaction and (ii) decomposition
reaction from the following chemical equations :
(a) C + O2 $ CO2 170. Reverse of the following chemical reaction is not
possible :
(b) NaBr + AgNO 3 $ AgBr + NaNO 3
Zn (s) + CuSO 4 (aq) $ ZnSO 4 (aq) + Cu (s)
CaO + CO2
T
(c) CaCO 3
Justify this statement with reason.
(d) H2 S + Cl2 $ 2Hcl + S Sol : Foreign 2011
Sol : Comp 2011

171. State the type of chemical reactions with chemical

163. Complete and balance the following:
equations that take place in the following :
(i) P + O2 $
(i) Magnesium wire is burnt in air.
(ii) MnSO 4 + H2 S $
Sol : OD 2006 (ii) Electric current is passed through water.
Sol : Delhi 2014

164. Write balanced equation for each of the following :

172. Giving chemical equation answer the following:
(i) Chlorine gas burns in hydrogen gas to give
(a) What happens when copper is heated in air ?
hydrogen chloride.
(b) What happens when the product obtained in
(ii) Hydrogen sulphide burns in air to give water and
above reaction is heated in hydrogen?
sulphur dioxide. Sol : OD 2007
Sol : Delhi 2017

173. What is the colour of FeSO 4 $ 7H2 O crystals ? How

165. List four observations that help us to determine
does this colour change upon heating ? Give balanced
whether a chemical reaction has taken place.
Sol : OD 2013 chemical equation for the change.
Sol : Delhi 2010

For solutions download NODIA app.

Page 16 Chemical Reactions and Equations Chap 1

174. (a) Why is combustion reaction an oxidation reaction? 181. Study the figure given below and answer the following
(b) How will you test whether the gas evolved in a questions :
reaction is hydrogen ?
Sol : Comp 2006

175. You must have tasted or smelt the containing food

materials left for a long time. Such foods taste and
smell bad. What is the reason for this, and the name
given to the phenomenon ? List two measures taken
at home to prevent it.
Sol : Foreign 2009

176. Write two examples of every day life, where redox

reactions are taking place.
Sol : Delhi 2017

177. Food items can be preserved for longer time when

kept in a refrigerator. What is the reason behind this
fact?
Sol : Comp 2011

178. A student has been collecting silver coins and copper (a) Name the process depicted in the diagram.
coins. One day she observed a black coating on copper
(b) Write the composition of the anode and the
coins. Which chemical phenomenon is responsible for
cathode.
these coatings? Write the chemical name of black and
green coatings. (c) Write the balanced chemical equation of the
Sol : Foreign 2009 reaction taking place in this case.
(d) The reaction does not take place if a few drops
of dilute sulphuric acid are not added to water.
Why?
Sol : SQP 2018
THREE MARKS QUESTIONS
182. In the electrolysis of water :
(a) Name the gases liberated at anode and cathode.
179. Identify the type of each of the following reactions
stating reason for your answers : (b) Why is it that the volume of gas collected on one
electrode is two times that on the other electrode?
(a) Fe2 O 3 + 2Al $ Al2 O 3 + 2Fe + heat
(c) What would happen if dil. H2 SO 4 is not added to
(b) Pb (NO 3) 2 + 2Kl $ Pbl2 + 2KNO 3
water ?
ZnO + CO2
heat
(c) ZnCO 3 Sol : SQP 2020
Sol : Comp 2021

For solutions download NODIA app. 183. Lead nitrate solution is added to a test tube containing
potassium iodide solution.
180. When hydrogen sulphide gas is passed through a blue (a) Write the name and colour of the compound
solution of copper sulphate, the colour of the solution precipitated.
fades and a black precipitate is obtained. (b) Write the balanced chemical equaiton for the
(a) Name the type of reaction mentioned above. reaction involved.
(b) Why does the colour of the solution fade away ? (c) Name the type of this reaction justifying your
answer.
(c) Write the chemical name of the black precipitate Sol : Comp 2019
formed.
(d) Give the balanced chemical equation for the
184. 1 g of copper powder was taken in a China dish and
reaction involved.
Sol : SQP 2021 heated. What change takes place on heating ? When
Page 17 Chemical Reactions and Equations Chap 1

hydrogen gas is passed over this heated substance, a 189. Give chemical explanation for evolution and absorption
visible change is seen in it, Give the chemical equations of heat in a chemical reaction.
Sol : Foreign 2017
of reactions, the name and the color of the products
formed in each case.
Sol : Delhi 2019
190. Name three chemical reactions in which heat is
evolved and three chemical reactions in which heat
185. What does a balanced chemical equation convey ? is absorbed.
Sol : Delhi 2018 Sol : Delhi 2013

A balanced chemical equation conveys the following

informations : 191. Illustrate an experiment in support of a combination
(i) Formulae of substances taking part in chemical reaction.
Sol : OD 2010
reaction, i.e., reactants.
(ii) Formulae of substances produced in the reaction,
i.e., products. 192. Illustrate an experiment to support a displacement
reaction.
(iii) The relative number of molecules of reactants and Sol : Delhi 2007
products.
(iv) The relative masses of reactants and products.
193. Design an activity to show a decomposition reaction
(v) The relative volumes of gaseous substances in which light is used to decompose a reactant. Write
involved in the reaction. chemical equation for the reaction and state its one
use.
186. What is a thermochemical equation ? Give two Sol : Comp 2010

examples.
Sol : OD 2009
194. Draw a labelled schematic diagram to show the
electrolysis of water. Why is the amount of gas
187. Write and balance the following questions presented collected in one of the test tubes in this activity is
to you as written statements : double of the amount collected in the other ?
(i) Magnesium carbonate plus hydrochloric acid
Sol : Foreign 2013
produces magnesium chloride plus water plus
carbon dioxide gas.
(ii) Aluminium plus chlorine gas produces aluminium 195. A, B and C are three elements which undergo chemical
trichloride.. reactions according to the following equations :
A2 O 3 + 2B $ B2 O 3 + 2A
(iii) Nitrogen plus hydrogen produces ammonia.
Sol : Delhi 2016 3CSO 4 + 2B $ B2 (SO 4) 3 + 3C
3CO + 2A $ A2 O 3 + 3C
188. In an experiment 20 g of zinc (A) was reacted with Answer the following questions with reasons :
20 g of iodine (B) in a 250 ml beaker containing 50 ml (a) Which element is the most reactive ?
water. Reaction proceeded with evolution of heat and (b) Which element is the least reactive ?
at the end, reaction mixture did not give any colour (c) What is the type of reactions listed above ?
on adding starch solution, but some zinc was found Sol : OD 2014

settling at the bottom.

Zn (s) + I2 (s) $ ZnI2 (s) + heat 196. Take 2 g silver chloride in a china dish and place it
(i) Is the reaction endothermic or exothermic ? in sunlight.
(ii) Out of the two reactants, Zn(s) and I2 (s) , which (a) Observe the colour of silver chloride after some
one is left unreacted ? Why? time.
(iii) How much of (A) and (B) should he taken so that (b) What type of reaction does take place ?
no reactant is left out at the end of the reaction ? (c) Write the chemical reaction for above observation.
Sol : Comp 2019
or
For solutions download NODIA app. What change will you observe if white silver chloride is
placed in sunlight ? Write an equation for the reaction
and the type of the reaction.
Sol : Delhi 2012
Page 18 Chemical Reactions and Equations Chap 1

197. Take a small amount of calcium oxide or quick lime in 204. (a) List two observations which will show that a
a beaker and slowly add water to this. chemical reaction has taken place.
(a) Is there any change in temperature ? (b) A solution X is used for white washing :
(b) What type of reaction is taking place ? (i) Write the chemical name and formula of X
(c) Write chemical equation for above reaction. (ii) How is X obtained from compound Y
Sol : Comp 2010
which reacts with dil. HCl to give brisk
effervescence due to colourless, odourless gas
198. Name the type of chemical reaction represented by which is soluble in water and non-supporter
the following equations : of combustion ? Write chemical equation for
(i) CaCO 3 (s)
Heat
CaO (s) + CO2 (g) the reactions involved in the preparation of
(ii) CaO (s) + H2 O (l) $ Ca (OH) 2 (aq) X from Y .
Sol : Comp 2011
(iii) Zn (s) + H2 SO 4 (aq) $ ZnSO 4 (aq) + H2 (g)
Sol : Delhi 2008
205. (a) Give an example for a combination reaction which
is exothermic.
199. Identify the substances that are oxidised and that are
reduced in the following reactions : (b) Identify oxidising agent, reducing agent in the
following reaction :
(i) ZnO + C $ Zn + CO
H2 S + Cl2 $ 2HCl + S
(ii) CuO + H2 $ Cu + H2 O
(c) Name the phenomenon due to which the taste
(iii) MnO2 + 4HCl $ MnCl2 + 2H2 O + Cl2 and smell of oily food changes when kept for a
Sol : Foreign 2006
long time in open. Suggest one method to prevent
it.
200. When a water insoluble substance X is added to Sol : OD 2009

dilute hydrochloric acid, a colourless and odourless

gas is evolved. When the gas is passed through lime 206. Take 3g of barium hydroxide in a test tube, now add
water, it turns milky. Write the chemical formula of about 2 g of ammonium chloride and mix the contents
X and the chemical equations involved. with the help of a glass rod. Now touch the test tube
Sol : Comp 2011, 07
from outside.
(i) What do you feel on touching the test tube ?
201. Account for the following :
(ii) State the inference about the type of reaction
(a) White silver chloride turns grey in sunlight.
occurred.
(b) Brown coloured copper powder on heating in air
(iii) Write the balanced chemical equation of the
turns into black coloured substance.
Sol : OD 2013 reaction involved.
Sol : CBSE 2016

202. Explain the following chemical changes, giving one

207. Look at the figure given below and answer the
example in each case :
following questions :
(i) Displacement or substitution,
(ii) Dissociation,
(iii) Isomerisation reaction.
Sol : Delhi 2015

203. Give one example each of the following decomposition

reactions. Write balanced equation is each case :
(i) The reaction which occurs on passing electric
current.
(ii) The reaction which occurs in the presence of
sunlight.
(iii) The reaction which occurs on heating of a
substance.
Sol : Comp 2012
Page 19 Chemical Reactions and Equations Chap 1

(i) What is the colour of ferrous sulphate crystals

before and after heating.
(ii) How do you identify the gases evolved on heating.
(iii) Write the balanced chemical equation. What kind
of reaction does it represent ?
Sol : Foreign 2007

208. State one example each characterized by the following

along with the chemical equation :
(a) Change in stable
(b) Evolution of gas
(c) Change in temperature.
Sol : OD 2014

209. On heating blue coloured powder of copper(II) nitrate

in a boiling tube, copper oxide (black), oxygen gas
and a brown gas X is formed.
(a) Write a balanced chemical equation of the
reaction. (i) Which tube contains hydrogen gas ?
(b) Identify the brown gas X evolved. (ii) If the volume of hydrogen gas collected is 10 mL,
(c) Identify the type of reaction. what will be the volume of oxygen collected ?
Sol : OD 2006
(iii) Why do we add a few drops of dil. sulphuric acid?
Sol : Delhi 2007
For solutions download NODIA app.
212. During the reaction of some metals with dilute
210. Look at the figure given below and answer the hydrochloric acid, following observations were made :
following questions : (i) The temperature of the reaction mixture rises
when aluminium (Al) is added.
(ii) The reaction of sodium metal is found to be
highly explosive.
(iii) Some bubbles of a gas are seen when lead (Pb) is
reacted with the acid.
Explain these observations giving suitable reasons.
Sol : OD 2009

213. State which of the following chemical reactions will

take place or not, giving suitable reason for each :
(i) Zn (s) + CuSO 4 (aq) $ ZnSO 4 (aq) + Cu (s)
(ii) Fe (s) + ZnSO 4 (aq) $ FeSO 4 (aq) + Zn (s)
(a) Write the chemical reaction involved.
(iii) Zn (s) + FeSO 4 (aq) $ ZnSO 4 (aq) + Fe (s)
(b) What are the colours of Cu and CuO ? Sol : Foreign 2011

(c) Can we reconvert CuO into Cu ? Write the

reaction involved. 214. Anhydrous copper sulphate (CuSO 4) was dissolved
Sol : Delhi 2011
in one beaker and hydrated copper sulphate
(CuSO 4 $ 5H2 O) was dissolved in another beaker.
211. Look at the figure given below and answer the What heat changes do you expect in these beakers
following questions : and why ?
Sol : Comp 2013

215. Tanya added magnesium into a test tube containing

dil. HCl acid. She saw some gas coming out of it. She
Page 20 Chemical Reactions and Equations Chap 1

took a burning match stick near the mouth of the test (iii) 2KClO 3 (s) $ 2KCl (aq) + 3O2 (g)
tube and heard a popping sound while the match stick (iv) Zn + CuSO 4 $ ZnSO 4 + Cu
extinguished. Tanya concluded that the gas evolved is (b) Translate the following statement into a balanced
hydrogen and it is not combustible. Find the error in chemical equation :
her conclusion and support your answer with reason. “Barium chloride reacts with aluminium sulphate
Sol : SQP 2016
to give aluminium chloride and barium sulphate.”
Sol : OD 2019

216. Justify with the help of an example that displacement

reaction is also a redox reaction. 222. What is observed after about 1 hour of adding the
Sol : OD 2013
strips of copper and aluminium separately to ferrous
sulphate solution filled in two beakers ?
217. Compound A when dissolved in water gives compound Name the reaction if any change in colour is noticed.
B and liberates heat. Compound A is used in white Also, write chemical equation for the reaction.
washing. Compound B reacts with CO2 to form a Sol : Foreign 2019

white precipitate of compound C . Identify compounds

A , B and C and also write the equations involved. 223. A student wants to study a decomposition reaction by
Sol : Delhi 2011
taking ferrous sulphate crystals. Write two precautions
he must observe while performing the experiment.
218. When CaO is added to water taken in a beaker, rise in Sol : Delhi 2019

temperature is observed. However, when Ba (OH) 2 is

mixed with NH 4 Cl , a fall in temperature is observed. 224. How is a chemical equation written ? Illustrate with
Why ? an example.
Sol : Foreign 2013
Sol : OD 2016

219. Give reasons for the following : 225. Describe the method of balancing a chemical equation.
(i) Keeping food in air tight containers help in Sol : Delhi 2012

preventing rancidity.
(ii) Moist air and acidic gases are not good for some 226. Balance the following skeleton equations :
metals. (i) KClO 3 $ KCl + O2
(iii) Chips manufacturers usually flush bags of chips (ii) Na2 CO 3 + HCl $ NaCl + H2 O + CO2
with nitrogen gas. (iii) CH 4 + O2 $ CO2 + H2 O
Sol : Comp 2015
(iv) NaCl + H2 SO 4 $ Na2 SO 4 + HCl
(v) Fe + H2 O $ Fe 3 O 4 + H2
FIVE MARKS QUESTIONS (vi) H2 S + O2 $ H2 O + S
(vii) H2 + N2 $ NH 3
Sol : Comp 2012

220. (a) Design an activity to demonstrate the

decomposition reaction of lead nitrate. 227. What are the drawbacks of a chemical equation?
Illustrate with an example.
(b) Draw labelled diagram of the experimental set- Sol : OD 2017
up. List two main observations.
(c) Write balanced chemical equation for the reaction
228. How can a chemical reaction be made more
stating the physical state of the reaction and the
informative?
products. Sol : Delhi 2010
Sol : Delhi 2019

229. Name the. type of following reactions :

221. (a) Classify the following reactions into different
(i) Fe (s) + CuSO 4 (aq) $ Cu (s) + FeSO 4 (aq)
types :
(ii) 2NH 3 (g) $ N2 (g) + 3H2 (g)
(i) AgNO 3 (aq) + NaCl (aq) $ AgCl (s)
+ NaNO 3 (aq) (iii) NH 4 Cl (s) $ NH 3 (g) + HCl (g)
(iv) 2H2 (g) + O2 (g) $ 2H2 O (g)
(ii) CaO (s) + H2 O (l) $ Ca (OH) 2 (aq)
(v) CuO (s) + H2 (g) $ Cu (s) + H2 O (l)
Page 21 Chemical Reactions and Equations Chap 1

(vi) NH 4 NO2 (s) $ 2H2 O (g) + N2 (g) (i) Write the complete balanced reaction for the
(vii) Mg (s) + H2 SO 4 (aq) $ MgSO 4 (aq) + H2 (g) above.
(viii) 2NH 3 (g) + H2 SO 4 (aq) $ (NH 4) 2 SO 4 (aq) (ii) Type of reaction involved.
Sol : Foreign 2016
(iii) Is there any precipitate formed?
(iv) If any precipitate formed, write the colour of the
230. Define the terms : precipitate.
Sol : Comp 2008
(i) Oxidising agent and
(ii) Reducing agent.
Sol : Delhi 2018
234. When a green salt is heated strongly, its colour finally
changes to brown and odour of burning sulphur is
231. (a) What happens chemically when quick lime is given out :
added to water ? (a) Name the iron salt and write its formula.
(b) Balance the following chemical equation : (b) Name the brown substance obtained and write its
MnO2 + HCl $ MnCl2 + Cl2 + H2 O formula.
(c) What is decomposition reaction? Explain it with (c) Which product gives the odour of burning
suitable example. sulphur? Write the formula.
Sol : Foreign 2010
(d) Write the chemical equation of the reaction
involved.
232. (a) Balance the chemical equation : (e) Name the type of chemical reaction which takes
Fe (s) + H2 O (g) $ Fe 3 O 4 (s) + H2 (g) place during the heating of iron salt.
(b) Identify the type of reaction in the equation given Sol : OD 2006

below :
Na2 SO 4 (aq) + BaCl2 (aq) $ BaSO 4 (s) 235. (a) Define corrosion.
+ NaCl (aq)
(b) What is the name given to the corrosion of iron ?
(c) You could have noted that when copper powder
(c) What is the colour of coating formed on silver and
is heated in a china dish, the surface of copper
copper ?
powder becomes coated with black colour
(d) What damage is caused by corrosion?
substance.
(e) How can we prevent corrosion ?
(i) Why has this black coloured substance Sol : Delhi 2011
formed?
(ii) What is that black substance ?
236. (i) Name two effects of oxidation in daily life.
(iii) Write the chemical equation of the reaction
(ii) Why do iron articles become brown after
that takes place.
Sol : OD 2013 sometime?
(iii) Define the term corrosion. Give an example of
corrosion.
233. Observe the given figure and answer the following
(iv) Give the conditions of corrosion.
questions :
(v) What is rancidity ?
Sol : Delhi 2014

For solutions download NODIA app.

237. Identify the type of chemical reaction and write

balanced chemical equation for each of the following:
(a) Barium chloride solution is mixed with copper
sulphate solution and a while precipitate is
observed.
(b) On heating copper powder in a china dish, the
surface of copper powder becomes black.
(c) On heating green ferrous sulphate crystals, a
reddish brown solid is left and gases having smell
Page 22 Chemical Reactions and Equations Chap 1

of burning sulphur are noticed. as combination reaction, decomposition reaction,

(d) Iron nails when left dipped in blue copper displacement reaction, double displacement reaction.
sulphate solution become brownish in colour and The reactions take place in solution is precipitation
blue colour of copper sulphate solution turns to reactions and neutralisation reactions.
light green.
(e) Quicklime reacts vigorously with water releasing
a large amount of heat.
Sol : Comp 2012

For solutions download NODIA app.

238. (a) Write a balanced chemical equation for the

process of photo synthesis and the conditions
of the reaction giving physical states of all the
substances.
(b) Classify the following chemical reactions as
exothermic or endothermic :
(i) Electrolysis of water.
(ii) Burning of natural gas.
(iii) Decomposition of calcium carbonate.
(iv) Burning of magnesium ribbon in air.
Sol : Comp 2008

(i) Define a chemical equation.

COMPETENCEY BASED QUESTIONS (ii) Which law is followed by all chemical reactions?
(iii) Name four types of chemical reactions.
(iv) Give example of precipitation reactions.
239. A student prepared oxygen in a lab by catalytic Sol :
decomposition of potassium chlorate ^KClO 3h as
shown in the figure. Decomposition of potassium 241. Corrosion is the phenomenon of deterioration of surface
chlorate gives potassium chloride (KCl) and oxygen of metal in presence of air and moisture. It is a natural
^O 2h . The following reaction takes place : process and in the presence of a moist atmosphere,
KClO 3 (s) $ KCl (s) + O 2 (g) chemically active metals get corroded. This is
oxidation reaction. Rusting is the process where iron
(i) How many moles of KClO 3 are required to
corrodes due to exposure to the atmosphere. The main
produce 2.4 moles of O 2 ?
circumstance of corrosion occurs with iron because
(ii) Name the element which is reduced in the given it is a structural material in construction, bridges,
reaction. buildings, rail transport, ships, etc. Aluminium is also
(iii) How many moles of KClO 3 give 3 moles of an important structural metal, but even aluminium
oxygen? undergoes oxidation reactions. However, aluminium
(iv) What is the oxidation state of chlorine in doesn’t corrode or oxidize as rapidly as its reactivity
potassium chlorate? suggests. An alloy of aluminium or any other metal
Sol :
like magnesium can make aluminium stronger and
harder.
240. When two or more substances react and form some Copper (Cu) corrodes and forms a basic green
new substance, it is called a chemical reaction. carbonate and lead corrodes to form a white lead
Chemical equation is represented in terms of symbols, oxide or carbonate.
molecular formulas, moles, states, etc. As we know, all (i) What is rusting?
chemical reaction obeys law of chemical combination.
(ii) Which two metals do not corrode easily?
Therefore, chemical reactions need to be balanced.
It is done by hit and trial method. The chemical (iii) List two properties of alloys.
reactions can be classified into different types such (iv) What is the effect of corresion on electrical
Page 23 Chemical Reactions and Equations Chap 1

conductivity ?

242. Oxidation is the process of gaining of oxygen or losing

of hydrogen. Reduction is the process of losing of
oxygen or gaining of hydrogen. The substance which
undergoes oxidation is the reducing agent while the
substance which undergoes reduction is known as the
oxidising agent. Oxidation and reduction always take
place together and these type of reactions are known
as redox reactions. Some of the examples of redox
reactions are given below :
a. Pb 3 O 4 + 8HCl $ 3PbCl 2 + Cl 2 + 4H 2 O
b. 2Mg + O 2 $ 2MgO
(i) Write the chemical reaction of chlor-alkali process.
c. CuSO 4 + Zn $ Cu + ZnSO 4
(ii) Name the gases formed at the anode and the
d. V2 O 5 + 5Ca $ 2V + 5CaO cathode.
e. 3Fe + 4H 2 O $ Fe 3 O 4 + 4H 2 (iii) Write one use each of chlorine and hydrogen gas.
(iv) How will you prepare baking soda from sodium
f. CuO + H 2 $ Cu + H 2 O
chloride?
(i) Give two examples of oxidation reaction from Sol :
your everyday life.
(ii) Write the oxidising agent in the reaction a and b. 244. There are different types of chemical reactions
(iii) Out of oxidation and reduction, which reaction occurring around us or being carried out for the
takes place at anode? benefit of mankind, e.g. combination reactions,
Sol :
decomposition reactions, displacement reactions,
precipitation reactions, reduction-oxidation (redox)
243. ‘Salts’ refer to the compound formed when an acid reactions, photochemical reactions etc.
reacts with a base. These reactions are known as Now, answer the following questions :
neutralisation reactions. These reactions are often used
(i) Combustion of coke is a combination reaction.
in the laboratories to calculate the exact concentration
CO 2 is not a pollutant. Then, why is combustion
of an acid or an alkali when the other is known. The
of coke harmful?
familiar example of salt is sodium chloride (NaCl),
(ii) Which reaction followed by two combination
which we use in our food on daily basis and is known
reactions are involved in white wash of walls?
as rock salt.
(iii) Give one use of tin plating in daily life.
It is prepared by the reaction of hydrochloric acid
and sodium hydroxide solution. This salt is used to (iv) How photochemical reactions have played an
prepare various compounds. When electricity is pass important in photography?
Sol :
through an aqueous solution of sodium chloride (called
brine), it decomposes to form sodium hydroxide. The
process is called the chlor-alkali process because of 245. Ferrous sulphate crystals on heating in a dry boiling
the products formed-chlor and alkali for sodium tube gives the following reaction:
Heat
hydroxide. 2FeSO 4 (s) Fe 2 O 3 (s) + SO 2 (g) + SO 3 (g)
(i) What is the colour change in this reaction ?
(ii) Name the type of reaction.
(iii) Which gas has a smell of burning sulphur?
(iv) What happens where SO 2 gas is passed through
water?
Sol :

246. While performing experiment in the chemistry lab, a

student took lead nitrate solution in a test tube. To
Page 24 Chemical Reactions and Equations Chap 1

this solution, he added potassium iodide solution. substances gets reduced.

(i) Write balanced chemical equation for this (iii) What name can be given to this reaction other
reaction. than redox reactions?
(ii) What are the different names given to this (iv) How will you test the gas evolved?
reaction? (v) Identifying the oxidizing agent and reducing
(iii) What is the colour of the precipitate formed? agent.
Sol :
(iv) Name the compound precipitated.
Sol :
251.

247. In a redox reaction, if a substance gains oxygen, it is

said to be oxidized. If a substance loses oxygen during
a reaction, it is said to be reduced.
In reaction:
Heat
CuO + H 2 Cu + H 2 O
(i) Which substance gets oxidized and which
substance gets reduced?
(ii) What is the colour change in the above reaction?
(iii) What other name is given to this redox reaction?
Heat
(iv) Is this reaction, ZnO + H 2 Zn + H 2 O
feasible? If not, then why?
Sol :

248. When a metal is attacked by substances around it

such as moisture, acids, etc., it is said to corrode, After seeing the above image answer the following
and this process is called corrosion. The black coating questions.
on silver, green coating on copper and reddish-brown (i) What was the colour of the crystals before heating
powder on iron surface are some examples of corrosion. and after heating?
(i) What is the name given to the corrosion of iron? (ii) Write the chemical equation for the reaction.
(ii) What is the formula of green colour coating on (iii) Name the reaction.
copper? (iv) Which pungent smelling gas is evolved during the
(iii) Name two methods to prevent corrosion of iron. reaction ? What is the nature of this gas?
(iv) Is corrosion a redox reaction? (v) Write the name of the solid substance formed.
Sol : Sol :

For solutions download NODIA app.

249. Magnesium ribbon burns in air with a dazzling white
flame. This is due to the formation of a white solid.
This white solid dissolves in water and gives a solution 252. (i) Write the balanced chemical equation for the
which turns red litmus blue. reaction. Name the reaction.
(i) Write the equation for the reaction of magnesium (ii) What is the colour of the precipitate formed and
ribbon in air. name the products formed in the reaction?
(ii) Name the type of reaction.
(iii) Why does the white dazzling flame appear ?
(iv) What happens when white solid is dissolved in
water?
Sol :

250. You are given the following unbalanced equations:

Fe (s) H 2 O (g) $ Fe 3 O 4 (s) + H 2 (g)
(i) Write balanced chemical equations.
(ii) Write which substance gets oxidized and which