Question

Consider the following proposed two-­‐step mechanism for the reaction: 2A + B à C + D. Step 1: A + B ⇄ E Step 2: E + A → C + D a. Is this a reasonable mechanism? Why or why not? b. What are the intermediates in the reaction mechanism? c. Write a rate law for each step. d. Write an overall rate law if the first step is very slow compared to the second step. e. Write an overall rate law if the second step is very slow compared to the first step. You can assume a rapid equilibration of the first step. f. Draw a potential energy diagram for each of the previous two parts. g. Do either of these mechanisms work if the experimental rate law is Rate = k[A]2[B].

Answer 1

Given that    2A + B -------------> C + D

   Step 1: A + B ⇄ E

Step 2: E + A → C + D

a) Yes. It has intermediate.

b) Intermediates = E

c) rate law for step 1 , rate = k[A] [B]

   rate law for step 2 , rate = k[E] [A]

d) Write an overall rate law if the first step is very slow compared to the second step.

rate =  k[A] [B]

e) Write an overall rate law if the second step is very slow compared to the first step.

  rate = k[E] [A]