Question

The following is a multi-step reaction. The rate-limiting step is unimolecular, with A as the sole reactant

.If [A] and [B] are both 0.195 M, then the rate of reaction is 0.0050 M/s.

(a) What is the rate of the reaction if [A] is doubled

(b) Starting with the original concentrations, what is the rate of the reaction if [B] is doubled?

(c) Starting with the original concentrations, what is the rate of the reaction if [A] and [B] are both increased by a factor of three?

Answer 1

Since rate limiting step depends only on A,

rate law can be written as:

rate = k [A]

a)

doubling [A] will double the rate

new rate = 2*old rate

= 2*0.0050 M/s

= 0.010 M/s

Answer: 0.010 M/s

b)

Rate law doesn’t depends on [B]

So, changing concentration of B would not have any effect.

Answer: 0.0050 M/s

c)

Changing [B] will not have any effect

But tripling concentration of A will triple the rate

new rate = 3*old rate

= 3*0.0050 M/s

= 0.015 M/s

Answer: 0.015 M/s