Ncert Exercises & Solutions

Select the correct option based on statements below:

Assertion (A):	The enthalpy of reaction remains constant in the presence of a catalyst.
Reason (R):	A catalyst participating in the reaction forms a different activated complex and lowers down the activation energy but the difference in energy of the reactant and the product remains the same.

1.	Both (A) and (R) are true and (R) is the correct explanation of (A).
2.	Both (A) and (R) are true but (R) is not the correct explanation of (A).
3.	(A) is true but (R) is false.
4.	Both (A) and (R) are false.

HINT: Catalyst only alters the rate of the reaction does not affect any thermodynamic properties.

Explanation:

Enthalpy of reaction i.e., a difference of total enthalpy of reactants and product remains constant in the presence of a

catalyst. As a catalyst participating in the reaction forms the different activated complex and lowers down the activation

energy but the difference in energy of reactant and product remains the same.

Hence, both assertion and reason are correct and the reason is the correct explanation of assertion.