Question

Consider the reaction:

2A + B → C + D

Following results were obtained in experiments designed to study the rate of reaction:

(a) Write the rate law for the reaction.
(b) Calculate the value of rate constant for the reaction.
(c) Which of the following possible reaction mechanism is consistent with the rate law found in (a)?

I.  A + B → C + E (slow)

    A + E → D (fast)

II.  B + C → E (slow)

A + E → F (fast)

A + F → D (fast)

Answer 1

Dividing equation (iii) by (ii), we get 

Dividing equation (ii) by (i), we get

 (c) The reaction mechanism (II) is consistent with the rate law found in (a).

Comments

On what basis did you get the answer for question (c) ?

Answer 2

a) We assume that Rate = k[A]^m [B]ⁿ 

∴ 1.5 x 10^-3 mol L^-1 min^-1 = k(0.1)^m (0.1)n...........(i)    

  3.0 x 10^-3 mol L^-1 min^-1 = k(0.2)^m (0.2)n .........(ii) 

  6.0 x 10^-3 mol L^-1 min^-1 = k(0.2)^m (0.4)ⁿ ..........(iii)

c) The reaction mechanism (II) is consistent with the rate law found in (a).because in reaction mechanism (II) it is rate determining process and products formation is slow and easily done due to less concentration of products. 

B + C → E (slow) 

Only product formation is 1. i:e (E). So it is slow and rate determining reaction.