The reaction 2NO2 → 2NO + O2 follows second-order kinetics. At 300 °C, [NO2] drops from 0.0100 M to 0.00650 M in 100.0 s. The rate constant for the reaction is ________ M-1s-1.

Question

A. 0.65

B. 0.81

C. 0.54

D. 1.2

E. 0.096

Answer 1

Since this is a 2nd order reaction, we can write the rate law as...

Rate = k[NO₂]²

The integrated rate law becomes 1/[A] = 1/[A]_o + kt

Plugging in the known values and solving for k, we have ...

1/0.00650 M = 1/0.0100 M + k(100.0 s)

153.8 M^-1 = 100 M^-1 + 100s x k

53.8 M^-1 = 100s x k

k = 0.538 M^-1s^-1 = 0.54 M^-1s^-1 (ANSWER B)