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

Step 1: Separate the two ideas.
This pair contrasts order with molecularity. Order is read off from the experimental rate law, while molecularity counts the molecules colliding in one single elementary step. Keep that distinction clear.

Step 2: Test the assertion.
Because order is found purely from the measured rate law, it can be quoted for any reaction at all, whether that reaction happens in a single step or unfolds over many steps. So the assertion is true.

Step 3: Test the reason.
Molecularity is meaningful only for one elementary step. A complex reaction is a chain of several steps, so the overall reaction has no single molecularity to speak of. So the reason is true.

Step 4: Do they connect.
Precisely because molecularity loses its meaning for a complex reaction, we lean on order to describe such reactions, so the reason correctly explains the assertion.
\[ \boxed{\text{Option (A): both true, R explains A}} \]