2A + B → Products is 3.78 x 10^(-4) M s^(-1) when the concentrations of A and B are 0.3 M each.

Question

The rate of a reaction, 

2A + B → Products is 3.78 x 10^-4 M s^-1 when the concentrations of A and B are 0.3 M each. If the rate constant of the reaction is 4.2 x 10^-3 s^-1 find the order of the reaction.

Answer 1

Given,

2A + B → Products

Rate = R = 3.78 x 10^-4 M s^-1

[A] = [B] = 0.3 M

Rate constant = 1 = 4.2 x 10^-3 s^-1

Let the order of the reaction in A be x and in B be y.

Then, by rate law,

Rate = R = k [A]^x [B]^y 3.78 x 10^-4

= 4.2 x 10^-3(0.3)^x(0.3)^y

= 4.2 x 10^-3(0.3)^x+y

= (0.3)^x+y

0.09 = (0.3)^x+y

(0.3)² = (0.3)^x+y

∴ x + y = 2 

Hence the order of overall reaction is 2.

∴ The order of the reaction is 2.