Consider the following reaction mechanism:
Step 1:
(CH3)3AuPH3 (CH3)3Au + PH3 (fast)
Step 2:
(CH3)3Au → C2H6+(CH3)Au (slow)
Step 3:
(CH3)Au + PH3 → (CH3)AUPH3 (fast)

Which step is the
rate-determining step?

a. step 1
b. step 2
c. step 3

Explanation:

The rate-determining step is always the slow step of a mechanism.

That is so, because it is the slow step which limits the reaction.

Imaging that for assembling a toy you have process of three steps:

The time to glue and hold one toy until the glue hardens determines that you can assemble 1 toy in 1 hour and not 60 toys or 30 toys.

Thus, the step that determines the rate at which the reaction happens is the slowest step: step 2.

i think the answer is terrae but not 100 percent sure. ▓▬▬ §