Question

Consider the following mechanism proposed for a reaction:

Step 1)	A + 2 B → C	(slow)
Step 2)	C + D → E	(fast)
Step 3)	E → A + F	(fast)

Give the overall reaction that results from this mechanism:

Based on the rate limiting step, what is the actual rate law for this mechanism?

Select all of the following species that are intermediates in this reaction.

E

B

F

C

A

D

Select all of the following species that are acting as catalysts in this reaction.

A

F

B

C

D

E

Answer 1

step 1 : A + 2 B → C (slow)

step 2 : C + D → E ( fast)

step 3 : E → A + F (fast)

Overall reaction is obtaines by adding the aboe three equations:

D + 2 B → F

In the above steps step(1) is the slowest step so it is the rate determining step.

In this slowest step it involves 1 mole of A & 2 moles of B but in the overall reaction there is no A

so the rate law be rate, r = k[B]²   ----(1)

The intermediates in the reaction are A , C & E

The species that is acting as a catalyst is A Since it participates in step(1) & is produced in step(3)