Question

Determine the rate law for the overall reaction (where the overall rate constant is represented as k).

Step 1 A -> B+C slow

step 2 C + D -> E fast

overall A+D -> B+E

Rate = ??

Answer 1

Let the rate law be r = k [A] ^m [B] ⁿ

Where m & n are the order of the reactions with respect to A & B

            r = rate of the reaction

           k = rate constant

Step 1: A B+C (slow)

step 2: C + D E ( fast)

overall reaction : A+D B+E

The order of the reaction can be determined experimentally.

So the slowest step gives order of the reaction.

The slowest step involves one molecule of the reactant A , so the order of the reaction is one with respect to A

Since in the slowest step doesn't involve the reactant D so the order of the reaction with respect to D is zero.

Therefore the rate law be r = k [A] ¹ [B] ⁰

                                        r = k [A]

This is the rate law