Question

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R: Assertion (A): A reaction can have zero activation energy. Reason (R): The minimum extra amount of energy absorbed by reactant molecules so that their energy becomes equal to threshold value, is called activation energy. In the light of the above statements, choose the correct answer from the options given below:

• A. Both A and R are true and R is the correct explanation of A
• B. Both A and R are true and R is NOT the correct explanation of A
• C. A is true but R is false
• D. A is false but R is true

Hint:

In Assertion-Reason questions, first check whether each statement is independently true, then verify whether the Reason logically explains the Assertion.

Answer 1

The Correct Option is B

Concept: Activation energy is the minimum energy required by reacting molecules to form the activated complex and undergo successful collision. According to collision theory, only those collisions which possess energy equal to or greater than activation energy lead to product formation. Some reactions, especially very fast ionic reactions, may have nearly zero activation energy.

Step 1: Analyze Assertion (A) Assertion states: \[ \text{A reaction can have zero activation energy.} \] This statement is true. Certain reactions occur so rapidly that practically no extra energy barrier exists between reactants and products. Such reactions are considered to have negligible or nearly zero activation energy. Examples include some ionic reactions occurring in aqueous medium. Therefore: \[ \text{Assertion A is true.} \]

Step 2: Analyze Reason (R) Reason states: \[ \text{Activation energy is the minimum extra energy required to reach threshold energy.} \] This is the correct definition of activation energy. Thus: \[ \text{Reason R is also true.} \]

Step 3: Check whether R explains A Although Reason correctly defines activation energy, it does not explain why some reactions can have zero activation energy. The statement in Reason is only a definition and does not justify the condition of zero activation energy. Hence: \[ \text{R is not the correct explanation of A.} \] Final Answer: \[ \boxed{\text{Both A and R are true and R is NOT the correct explanation of A}} \]