Question

Assertion (A): Order of reaction is applicable to elementary as well as complex reactions.
Reason (R): For a complex reaction, molecularity has no meaning.

• A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Assertion (A) is false, but Reason (R) is true.

Hint:

Order comes from experiment (any reaction); molecularity applies only to a single step.

Answer 1

The Correct Option is A

Concept: This question compares two ideas, order and molecularity. Order comes from experiment, from the measured rate law. Molecularity is the count of molecules that come together in one single step.

Step 1: Check the Assertion
Order is found from the experimental rate law, so it can be given for any reaction, whether it happens in one step (elementary) or in many steps (complex). So the Assertion is true.

Step 2: Check the Reason
Molecularity only makes sense for a single step, where we can actually count the colliding molecules. A complex reaction is a chain of several steps, so we cannot give one molecularity for the overall reaction. So the Reason is true.

Step 3: Do they connect
Because molecularity has no meaning for a complex reaction, we are forced to describe such reactions using order instead. So the Reason explains exactly why order is the quantity we use, that is, it explains the Assertion.

Answer: Option (A), both are true and R correctly explains A.