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JEE Main 2025 Apr 2 Shift 2, Chemistry Q14: Rate Of A Chemical Reaction

JEE Main2025Apr 2, Shift 2Chemistry
Q.

Reactant A converts to product D through the given mechanism (with the net evolution of heat) :

A B slow ;

B C fast ;

C D fast ;

Which of the following represents the above reaction mechanism ?

  1. A

    1

  2. B

    2

  3. C

    3

  4. D

    4

Solution

Three sequential elementary steps demand three barriers on the energy profile.

Step 1 (A B) is slow and endothermic: it must have the highest activation energy, and intermediate B should sit above A in energy.

Steps 2 and 3 (B C and C D) are fast and exothermic: each barrier is smaller than the first, and the energy drops further at each intermediate.

The overall process evolves heat, so D lies below A.

The profile that matches all of these features is diagram (1).

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