Question

Assertion (A): For complex reactions, order of reaction is given by the fast step.
Reason (R): Order of reaction is determined experimentally.

• A. Both A and R are true and R is the correct explanation of A.
• B. Both A and R are true but 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:

Rate-determining step = Slowest step, not fastest. Overall order is always found experimentally.

Answer 1

The Correct Option is D

Step 1: Check the Assertion.
For a complex (multi-step) reaction, the overall rate is determined by the SLOWEST step (rate-determining step), not the fast step. The Assertion states the fast step governs order, which is WRONG. Assertion is FALSE.
Step 2: Check the Reason.
The overall order of a reaction cannot be deduced from the stoichiometry of the balanced equation; it must be found experimentally by measuring how rate changes with concentration. Reason is TRUE.
Step 3: Conclusion.
A is false (should say slow step, not fast step) but R is a correct and independently valid statement.
\[ \boxed{\text{A is false; R is true}} \]