October 12, 2021

Scientific Knowledge

“Learning is never done without errors.”

Chemical Reactions and Equations : Assertion and Reason

1. Chemical Reaction and Equations

ASSERTION (A) AND REASON (R) Types questions

DIRECTION: Each of these questions contains an Assertion (A) followed by Reason (R). Read them carefully and answer the question on the basis of following options. You have to select the one that best describes the two statements.

(a)  Both Assertion (A) and Reason (R) are correct and Reason (R) is the correct explanation of Assertion (A).

(b) Both Assertion (A) and Reason (R) are correct, but Reason (R) is not the correct explanation of Assertion (A).

(c) Assertion (A) is correct but Reason (R) is incorrect.

(d) Assertion (A) is incorrect but Reason (R) is correct

(e) Both Assertion (A) and Reason (R) are false

 

1. Assertion (A): White silver chloride turns grey in sunlight.

Reason (R): Decomposition of silver chloride in presence of sunlight takes place to form silver metal and chlorine gas.

Ans.: (a) Both Assertion (A) and Reason (R) are correct and Reason (R) is the correct explanation of Assertion (A).

 

2. Assertion (A): Pungent smelling gas is produced when sulphur burns in air.

Reason (R): Sulphur trioxide is formed on reaction of sulphur with oxygen.

Ans.: (c) Assertion (A) is correct but Reason (R) is incorrect.

 

3. Assertion (A): In a reaction of copper with oxygen, copper serves as a reducing agent.

Reason (R): The substance which gains oxygen in a chemical reaction is reducing agents.

Ans.: (a) Both Assertion (A) and Reason (R) are correct and Reason (R) is the correct explanation of Assertion (A).

 

4. Assertion (A): The following chemical equation, 2C6H6 + 7 O2 ➔  4CO2 + 3H2O

is a balanced chemical equation.

Reason (R): In a balanced chemical equation, the total number of atoms of each element may or may not equal on both side of the equation.

Ans.: (e) Both Assertion (A) and Reason (R) are false.

Explanation: In a balanced chemical equation, the total number of atoms of each element is equal on both sides of the equation.

The correct balanced chemical equation is, 2C2H6 + 7O2  ➔  4CO2 + 6H2O

 

Revision Notes for Class – 6th to 12th

 

5. Assertion (A): Fe2O3 + 2Al ➔  Al2O3 + 2Fe

The above chemical equation is an example of displacement reaction.

Reason (R): Aluminium being more reactive than iron, displaces Fe from its oxide.

Ans.: (a) Both Assertion (A) and Reason (R) are correct and Reason (R) is the correct explanation of Assertion (A).

Explanation: Fe2O3 + 2Al  ➔  Al2O3 + 2Fe is a displacement reaction, Here, a highly reactive element (Al) displaces Fe from Fe2O3.

 

6. Assertion (A): In the following chemical equation, CuO(s) + Zn(s) ➔ ZnO (s) + Cu(s)

Zinc is getting oxidized and copper oxide is getting reduced.

Reason (R): The process in which oxygen is added to a substance is called oxidation whereas the process in which oxygen is removed from a substance is called reduction.

Ans.: (a) Both Assertion (A) and Reason (R) are correct and Reason (R) is the correct explanation of Assertion (A).

Explanation: Because the reaction involves both oxidation and reduction in which, CuO is reduced to Cu and Zn is oxidised to ZnO.

 

7. Assertion (A): Quicklime reacts vigorously with water releasing a large amount of heat.

Reason (R): The above chemical reaction is an exothermic reaction.

Ans.: (a) Both Assertion (A) and Reason (R) are correct and Reason (R) is the correct explanation of Assertion (A).

Explanation: Because in exothermic reactions, hear is released along with the formation of products.

 

8. Assertion (A): Photosynthesis is considered as an endothermic reaction.

Reason (R): Energy gets released in the process of photosynthesis.

Ans.: (c) Assertion (A) is correct but Reason (R) is incorrect.

Assertion (A) is true but Reason (R) is false.

Explanation: Photosynthesis is considered as an endothermic reaction because energy in the form of sunlight is absorbed by the green plants.

 

9. Assertion (A): In a reaction – Zn(s) + CuSO4 (aq) ➔  ZnSO4 (aq) + Cu(s), Zn is a reducing agent but itself get oxidized.

Reason (R): In a Redox reaction, oxidising agent is reduced by accepting electrons and reducing agent is oxidized by losing electrons.

Ans.: (a) Both Assertion (A) and Reason (R) are correct and Reason (R) is the correct explanation of Assertion (A).

 

10. Assertion (A): Brown fumes are produced when lead nitrate is heated.

Reason (R): Nitrogen dioxide gas is produced as a by product due to the decomposition of lead nitrate.

Ans.: (a) Both Assertion (A) and Reason (R) are correct and Reason (R) is the correct explanation of Assertion (A).

 

Chemical Reaction and Equations Revision Notes

 

11. Assertion (A): White silver chloride turns grey in sunlight.

Reason (R): Decomposition of silver chloride in presence of sunlight takes place to form silver metal and chlorine gas.

Ans.: (a) Both Assertion (A) and Reason (R) are correct and Reason (R) is the correct explanation of Assertion (A).

 

 

12. Assertion (A): Pungent smelling gas is produced when Sulphur burns in air.

Reason (R): Sulphur trioxide is formed on reaction of Sulphur with oxygen.

Ans.: (c) Assertion (A) is correct but Reason (R) is incorrect.

 

13. Assertion (A): In a reaction of copper with oxygen, copper serves as a reducing agent.

Reason (R): The substance which gains oxygen in a chemical reaction is reducing agents.

Ans.: (a) Both Assertion (A) and Reason (R) are correct and Reason (R) is the correct explanation of Assertion (A).

 

14. Assertion (A): The following chemical equation, 2C6H6 + 7 O2 ➔  4CO2 + 3H2O

is a balanced chemical equation.

Reason (R): In a balanced chemical equation, the total number of atoms of each element may or may not equal on both side of the equation.

Ans.: (e) Both Assertion (A) and Reason (R) are false.

Explanation: In a balanced chemical equation, the total number of atoms of each element is equal on both sides of the equation.

The correct balanced chemical equation is, 2C2H6 + 7O2  ➔  4CO2 + 6H2O

 

CBSE Notes for Class-10th Science

 

15. Assertion (A): Fe2O3 + 2Al ➔  Al2O3 + 2Fe

The above chemical equation is an example of displacement reaction.

Reason (R): Aluminium being more reactive than iron, displaces Fe from its oxide.

Ans.: (a) Both Assertion (A) and Reason (R) are correct and Reason (R) is the correct explanation of Assertion (A).

Explanation: Fe2O3 + 2Al  ➔  Al2O3 + 2Fe is a displacement reaction, Here, a highly reactive element (Al) displaces Fe from Fe2O3.

 

16. Assertion (A): In the following chemical equation, CuO(s) + Zn(s) ➔ ZnO (s) + Cu(s)

Zinc is getting oxidised and copper oxide is getting reduced.

Reason (R): The process in which oxygen is added to a substance is called oxidation whereas the process in which oxygen is removed from a substance is called reduction.

Ans.: (a) Both Assertion (A) and Reason (R) are correct and Reason (R) is the correct explanation of Assertion (A).

Explanation: Because the reaction involves both oxidation and reduction in which, CuO is reduced to Cu and Zn is oxidised to ZnO.

 

17. Assertion (A): Quicklime reacts vigorously with water releasing a large amount of heat.

Reason (R): The above chemical reaction is an exothermic reaction.

Ans.: (a) Both Assertion (A) and Reason (R) are correct and Reason (R) is the correct explanation of Assertion (A).

Explanation: Because in exothermic reactions, hear is released along with the formation of products.

 

18. Assertion (A): Photosynthesis is considered as an endothermic reaction.

Reason (R): Energy gets released in the process of photosynthesis.

Ans.: (c) Assertion (A) is correct but Reason (R) is incorrect.

Assertion (A) is true but Reason (R) is false.

Explanation: Photosynthesis is considered as an endothermic reaction because energy in the form of sunlight is absorbed by the green plants.

 

19. Assertion (A): In a reaction – Zn(s) + CuSO4 (aq) ➔  ZnSO4 (aq) + Cu(s), Zn is a reducing agent but itself get oxidized.

Reason (R): In a Redox reaction, oxidising agent is reduced by accepting electrons and reducing agent is oxidized by losing electrons.

Ans.: (a) Both Assertion (A) and Reason (R) are correct and Reason (R) is the correct explanation of Assertion (A).


Chemical Reactions and Equations : Assertion and Reason type questions?

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