Question

Consider the reaction:

Consider the fictional reaction:

A + B → F + G

which is catalyzed by reagent C.

The rate of this reaction was monitored by looking at the disappearance of B under several different experimental setups at 298 K.

Experiment	[A] (M)	[B] (M)	[C] (M)	Rate of disappearance of B (M/s)
1	0.300	0.0500	0.100	0.000107
2	0.400	0.0500	0.200	0.000286
3	0.400	0.0500	0.0500	7.14e-05
4	0.300	0.0500	0.0500	5.36e-05
5	0.300	0.100	0.0500	5.36e-05

Step 1: A + C → D
Step 2: D → E + C
Step 3: E + B → F + G

Given the previous information, which of the following situations would lead to a plausible reaction mechanism?


Incorrect Step 2 as the rate determining step. All other steps fast steps.
Incorrect Step 3 as the rate determining step. All other steps fast steps.
Incorrect Step 3 as the rate determining step. Step 2 is a fast equilibrium step while step 1 is a fast step.
Correct: Step 2 as the rate determining step. Step 1 is a fast equilibrium step while step 3 is a fast step.

How is this the answer and how is the fast equilibrium step determined???