Textbook Solutions: Chemical Reactions and Equations

 Page 1


Chemical Reactions & Equations 
Exercise 
Q. 1. Choose the correct option from the bracket and explain the statement giving reason. 
 
(Oxidation, displacement, electrolysis, reduction, zinc, copper, double displacement, 
decomposition) 
a. To prevent rusting, a layer of ........ metal is applied on iron sheets. 
b. The conversion of ferrous sulphate to ferric sulphate is ........ reaction. 
c. When electric current is passed through acidulated water ........ of water takes place. 
d. Addition of an aqueous solution of ZnSO4 to an aqueous solution of BaCl2is an example 
of ....... reaction. 
Answer : a. To prevent rusting, a layer of zinc metal is applied on iron sheets. 
Explanation: 
Galvanization is a method to prevent rusting. 
i. In this method, a thin layer of zinc is applied on iron sheets to prevent rusting/corrosion. 
ii. First rusting of zinc takes place (more electropositive than iron). 
iii. After few seasons, zinc layer goes away. 
iv. Then, iron starts rusting. 
 
b. The conversion of ferrous sulphate to ferric sulphate is oxidation reaction. 
Explanation: 
Oxidation means losing of electrons. 
2FeSO4? Fe2(SO4)3 
Page 2


Chemical Reactions & Equations 
Exercise 
Q. 1. Choose the correct option from the bracket and explain the statement giving reason. 
 
(Oxidation, displacement, electrolysis, reduction, zinc, copper, double displacement, 
decomposition) 
a. To prevent rusting, a layer of ........ metal is applied on iron sheets. 
b. The conversion of ferrous sulphate to ferric sulphate is ........ reaction. 
c. When electric current is passed through acidulated water ........ of water takes place. 
d. Addition of an aqueous solution of ZnSO4 to an aqueous solution of BaCl2is an example 
of ....... reaction. 
Answer : a. To prevent rusting, a layer of zinc metal is applied on iron sheets. 
Explanation: 
Galvanization is a method to prevent rusting. 
i. In this method, a thin layer of zinc is applied on iron sheets to prevent rusting/corrosion. 
ii. First rusting of zinc takes place (more electropositive than iron). 
iii. After few seasons, zinc layer goes away. 
iv. Then, iron starts rusting. 
 
b. The conversion of ferrous sulphate to ferric sulphate is oxidation reaction. 
Explanation: 
Oxidation means losing of electrons. 
2FeSO4? Fe2(SO4)3 
Ionic reaction Fe
2+
 + SO4
2-
? 2Fe
3+
 + 3SO4
2-
 
As we can observe that in ionic reaction that Fe
2+
 changes to Fe
3+
. In this, the positive charge 
increases by one unit. This means ferrous ion loses one electron. Thus, the above reaction is an 
oxidation reaction. 
c. When electric current is passed through acidulated water electrolysis of water takes place. 
Explanation: 
On passing electric current through acidulated water (a water contains acid), water decomposes 
into hydrogen and oxygen gases. This decomposition takes place due to the presence of electrical 
energy. The reaction takes place is called electrolysis. 
Electrolysis: 2H2O(l) ? 2H2? + O2? 
 
d. Addition of an aqueous solution of ZnSO4 to an aqueous solution of BaCl2 is an example 
of double displacement reaction. 
Explanation: 
On addition of ZnSO4 and BaCl2, the following reaction takes place: 
ZnSO4 + BaCl2? ZnCl2 + BaSO4 
In the reaction, the exchange of ions are taking place. The reaction in which exchange of ions 
take place to form precipitate are called double displacement reaction. 
Page 3


Chemical Reactions & Equations 
Exercise 
Q. 1. Choose the correct option from the bracket and explain the statement giving reason. 
 
(Oxidation, displacement, electrolysis, reduction, zinc, copper, double displacement, 
decomposition) 
a. To prevent rusting, a layer of ........ metal is applied on iron sheets. 
b. The conversion of ferrous sulphate to ferric sulphate is ........ reaction. 
c. When electric current is passed through acidulated water ........ of water takes place. 
d. Addition of an aqueous solution of ZnSO4 to an aqueous solution of BaCl2is an example 
of ....... reaction. 
Answer : a. To prevent rusting, a layer of zinc metal is applied on iron sheets. 
Explanation: 
Galvanization is a method to prevent rusting. 
i. In this method, a thin layer of zinc is applied on iron sheets to prevent rusting/corrosion. 
ii. First rusting of zinc takes place (more electropositive than iron). 
iii. After few seasons, zinc layer goes away. 
iv. Then, iron starts rusting. 
 
b. The conversion of ferrous sulphate to ferric sulphate is oxidation reaction. 
Explanation: 
Oxidation means losing of electrons. 
2FeSO4? Fe2(SO4)3 
Ionic reaction Fe
2+
 + SO4
2-
? 2Fe
3+
 + 3SO4
2-
 
As we can observe that in ionic reaction that Fe
2+
 changes to Fe
3+
. In this, the positive charge 
increases by one unit. This means ferrous ion loses one electron. Thus, the above reaction is an 
oxidation reaction. 
c. When electric current is passed through acidulated water electrolysis of water takes place. 
Explanation: 
On passing electric current through acidulated water (a water contains acid), water decomposes 
into hydrogen and oxygen gases. This decomposition takes place due to the presence of electrical 
energy. The reaction takes place is called electrolysis. 
Electrolysis: 2H2O(l) ? 2H2? + O2? 
 
d. Addition of an aqueous solution of ZnSO4 to an aqueous solution of BaCl2 is an example 
of double displacement reaction. 
Explanation: 
On addition of ZnSO4 and BaCl2, the following reaction takes place: 
ZnSO4 + BaCl2? ZnCl2 + BaSO4 
In the reaction, the exchange of ions are taking place. The reaction in which exchange of ions 
take place to form precipitate are called double displacement reaction. 
 
Q. 2 A. Write answers to the following. 
 
What is the reaction called when oxidation and reduction take place simultaneously? 
Explain with one example. 
Answer : When oxidation and reduction takes place simultaneously, the reaction is called redox 
reaction. 
Oxidation: losing of electrons Reduction: gaining of electrons 
Redox Reaction = Reduction + oxidation 
For example: 
CuO + H2? Cu + H2O 
i. In the reaction, CuO loses oxygen atom which means that reduction of CuO(copper oxide) 
takes place. 
ii. H2 (hydrogen) takes up oxygen atom. 
iii. As a result, formation of water takes place. This means hydrogen undergoes oxidation. 
iv. Oxidation and reduction are taking place at the same time, thus it a redox reaction. 
Another example: 
Page 4


Chemical Reactions & Equations 
Exercise 
Q. 1. Choose the correct option from the bracket and explain the statement giving reason. 
 
(Oxidation, displacement, electrolysis, reduction, zinc, copper, double displacement, 
decomposition) 
a. To prevent rusting, a layer of ........ metal is applied on iron sheets. 
b. The conversion of ferrous sulphate to ferric sulphate is ........ reaction. 
c. When electric current is passed through acidulated water ........ of water takes place. 
d. Addition of an aqueous solution of ZnSO4 to an aqueous solution of BaCl2is an example 
of ....... reaction. 
Answer : a. To prevent rusting, a layer of zinc metal is applied on iron sheets. 
Explanation: 
Galvanization is a method to prevent rusting. 
i. In this method, a thin layer of zinc is applied on iron sheets to prevent rusting/corrosion. 
ii. First rusting of zinc takes place (more electropositive than iron). 
iii. After few seasons, zinc layer goes away. 
iv. Then, iron starts rusting. 
 
b. The conversion of ferrous sulphate to ferric sulphate is oxidation reaction. 
Explanation: 
Oxidation means losing of electrons. 
2FeSO4? Fe2(SO4)3 
Ionic reaction Fe
2+
 + SO4
2-
? 2Fe
3+
 + 3SO4
2-
 
As we can observe that in ionic reaction that Fe
2+
 changes to Fe
3+
. In this, the positive charge 
increases by one unit. This means ferrous ion loses one electron. Thus, the above reaction is an 
oxidation reaction. 
c. When electric current is passed through acidulated water electrolysis of water takes place. 
Explanation: 
On passing electric current through acidulated water (a water contains acid), water decomposes 
into hydrogen and oxygen gases. This decomposition takes place due to the presence of electrical 
energy. The reaction takes place is called electrolysis. 
Electrolysis: 2H2O(l) ? 2H2? + O2? 
 
d. Addition of an aqueous solution of ZnSO4 to an aqueous solution of BaCl2 is an example 
of double displacement reaction. 
Explanation: 
On addition of ZnSO4 and BaCl2, the following reaction takes place: 
ZnSO4 + BaCl2? ZnCl2 + BaSO4 
In the reaction, the exchange of ions are taking place. The reaction in which exchange of ions 
take place to form precipitate are called double displacement reaction. 
 
Q. 2 A. Write answers to the following. 
 
What is the reaction called when oxidation and reduction take place simultaneously? 
Explain with one example. 
Answer : When oxidation and reduction takes place simultaneously, the reaction is called redox 
reaction. 
Oxidation: losing of electrons Reduction: gaining of electrons 
Redox Reaction = Reduction + oxidation 
For example: 
CuO + H2? Cu + H2O 
i. In the reaction, CuO loses oxygen atom which means that reduction of CuO(copper oxide) 
takes place. 
ii. H2 (hydrogen) takes up oxygen atom. 
iii. As a result, formation of water takes place. This means hydrogen undergoes oxidation. 
iv. Oxidation and reduction are taking place at the same time, thus it a redox reaction. 
Another example: 
 
Q. 2. B. Write answers to the following. 
 
How can the rate of the chemical reaction, namely, decomposition of hydrogen peroxide be 
increased? 
Answer : Decomposition of hydrogen peroxide is a slow process: 
2H2O2(l) ? 2H2O + O2? (slow reaction) 
But we can increase the rate of reaction by using a particular catalyst, i.e., Manganese dioxide 
powder (MnO2). 
 
A catalyst is a substance which increases the rate of reaction without causing any chemical 
change. 
Q. 2. C. Write answers to the following. 
 
Explain the term reactant and product giving examples. 
Answer : Reactants – The substances which take part in a chemical reaction are called 
reactants. 
Products – The substances which are formed due to the formation of new bonds in a chemical 
reaction are called products. 
For example: 
 
Here, H2 and O2 take part in the chemical reaction, hence they are reactants. H2O is formed by 
the formation of new bonds; hence it is a product. 
Page 5


Chemical Reactions & Equations 
Exercise 
Q. 1. Choose the correct option from the bracket and explain the statement giving reason. 
 
(Oxidation, displacement, electrolysis, reduction, zinc, copper, double displacement, 
decomposition) 
a. To prevent rusting, a layer of ........ metal is applied on iron sheets. 
b. The conversion of ferrous sulphate to ferric sulphate is ........ reaction. 
c. When electric current is passed through acidulated water ........ of water takes place. 
d. Addition of an aqueous solution of ZnSO4 to an aqueous solution of BaCl2is an example 
of ....... reaction. 
Answer : a. To prevent rusting, a layer of zinc metal is applied on iron sheets. 
Explanation: 
Galvanization is a method to prevent rusting. 
i. In this method, a thin layer of zinc is applied on iron sheets to prevent rusting/corrosion. 
ii. First rusting of zinc takes place (more electropositive than iron). 
iii. After few seasons, zinc layer goes away. 
iv. Then, iron starts rusting. 
 
b. The conversion of ferrous sulphate to ferric sulphate is oxidation reaction. 
Explanation: 
Oxidation means losing of electrons. 
2FeSO4? Fe2(SO4)3 
Ionic reaction Fe
2+
 + SO4
2-
? 2Fe
3+
 + 3SO4
2-
 
As we can observe that in ionic reaction that Fe
2+
 changes to Fe
3+
. In this, the positive charge 
increases by one unit. This means ferrous ion loses one electron. Thus, the above reaction is an 
oxidation reaction. 
c. When electric current is passed through acidulated water electrolysis of water takes place. 
Explanation: 
On passing electric current through acidulated water (a water contains acid), water decomposes 
into hydrogen and oxygen gases. This decomposition takes place due to the presence of electrical 
energy. The reaction takes place is called electrolysis. 
Electrolysis: 2H2O(l) ? 2H2? + O2? 
 
d. Addition of an aqueous solution of ZnSO4 to an aqueous solution of BaCl2 is an example 
of double displacement reaction. 
Explanation: 
On addition of ZnSO4 and BaCl2, the following reaction takes place: 
ZnSO4 + BaCl2? ZnCl2 + BaSO4 
In the reaction, the exchange of ions are taking place. The reaction in which exchange of ions 
take place to form precipitate are called double displacement reaction. 
 
Q. 2 A. Write answers to the following. 
 
What is the reaction called when oxidation and reduction take place simultaneously? 
Explain with one example. 
Answer : When oxidation and reduction takes place simultaneously, the reaction is called redox 
reaction. 
Oxidation: losing of electrons Reduction: gaining of electrons 
Redox Reaction = Reduction + oxidation 
For example: 
CuO + H2? Cu + H2O 
i. In the reaction, CuO loses oxygen atom which means that reduction of CuO(copper oxide) 
takes place. 
ii. H2 (hydrogen) takes up oxygen atom. 
iii. As a result, formation of water takes place. This means hydrogen undergoes oxidation. 
iv. Oxidation and reduction are taking place at the same time, thus it a redox reaction. 
Another example: 
 
Q. 2. B. Write answers to the following. 
 
How can the rate of the chemical reaction, namely, decomposition of hydrogen peroxide be 
increased? 
Answer : Decomposition of hydrogen peroxide is a slow process: 
2H2O2(l) ? 2H2O + O2? (slow reaction) 
But we can increase the rate of reaction by using a particular catalyst, i.e., Manganese dioxide 
powder (MnO2). 
 
A catalyst is a substance which increases the rate of reaction without causing any chemical 
change. 
Q. 2. C. Write answers to the following. 
 
Explain the term reactant and product giving examples. 
Answer : Reactants – The substances which take part in a chemical reaction are called 
reactants. 
Products – The substances which are formed due to the formation of new bonds in a chemical 
reaction are called products. 
For example: 
 
Here, H2 and O2 take part in the chemical reaction, hence they are reactants. H2O is formed by 
the formation of new bonds; hence it is a product. 
Q. 2. D. Write answers to the following. 
 
Explain the types of reaction with reference to oxygen and hydrogen. Illustratre with 
examples. 
Answer : Types of reaction with reference to oxygen and hydrogen: 
i. Decomposition reaction 
2H2O2? 2H2O + O2 
In this reaction hydrogen peroxide undergoes decomposition 
to form water and oxygen gas. 
ii. Redox reaction 
CuO + H2? Cu + H2O 
In this reaction, oxidation and reduction taking place at the 
same time. 
iii. Electrolysis of water (decomposition) 
2H2O(l) ? 2H2? + O2? 
In this decomposition of water takes place to release hydrogen and oxygen gas. 
Q. 2. E. Write answers to the following. 
 
Explain the similarity and difference in two events, namely adding NaOH to water and 
adding CaO to water. 
Answer : Reaction between NaOH and water: NaOH + H2O ? Na
+
 + OH
-
 
Reaction between CaO and water : CaO + H2O ? Ca(OH)2 + heat