Question

A) 2A → B + C

The above reaction is run and found to follow first order kinetics with a rate constant of 1.30 x 10^-3 sec^-1. If the initial concentration of A is 1.72 M, what is the concentration after 152 seconds?

B) 2A → B + C

The above reaction is run and found to follow second order kinetics with a rate constant of 1.30 x 10^-3 M^-1sec^-1. If the initial concentration of A is 1.66 M, what is the concentration after 117 seconds?

C)2A → B + C

The above reaction is run and found to follow zero order kinetics with a rate constant of 1.30 x 10^-3 M•sec^-1. If the initial concentration of A is 1.4 M, what is the concentration after 195 seconds?

Answer 1

A) Rate constant, k = 1.30 x 10^-3 M^-1sec^-1

Initial concentration of A = 1.72 M

Time (t) = 152 sec

For first order kinetics

ln (Ao/A_t) = kt

ln (1.72/A_t) = 1.30 x 10^-3 x 152

ln (1.72/A_t) = 0.1976

(1.72/A_t) = e^+0.1976 = 1.2185

A_t = 1.72/1.2185

At = 1.412 M

B)

Rate constant, k = 1.30 x 10^-3 M^-1sec^-1.

Initial concentration of A = 1.66 M

Time (t) = 117 sec

For second order kinetics

k = (1/t) {1/[ A] - 1/ [A₀] }

1.30 x 10^-3 = (1/117) {(1/[ A]) – (1/ 1.66)}

152.1 x 10^-3 = (1/[ A]) – (1/ 1.66)

1/[ A] = 0.1521 + 0.6024 = 0.7545

[A] = 1.3254 M

C)

Rate constant, k = 1.30 x 10^-3 M^-1sec^-1.

Initial concentration of A = 1.4 M

Time (t) = 195 sec

For zero order kinetics

Ao = At + kt

1.4 = At + 1.30 x 10^-3 x 195

At = 1.4 - 0.2535

At = 1.1465 M