Question

At very low concentrations of azomethane, its decomposition follows which order?

(a) First order

(b) Zero order

(c) Third order

(d) Second order

This question was posed to me by my school principal while I was bunking the class.

The origin of the question is Reducing the Size of Kinetic Models topic in division Elements of Reaction Kinetics of Chemical Reaction Engineering

Answer 1

The correct answer is (d) Second order

Explanation: The rate expression for decomposition of azomethane is:

rN2 = \(\frac{k_1 k_3 C_{Azo}^2}{k_3+k_2 C_{Azo}} \)

Where, k1, k2 and k3 are rate constants of the 3 intermediate reactions involved in azomethane formation.

At low concentration, k2 CAzo << k3

Hence, rN2=k1CAzo^2.