2002 AIPMT Chemical KineticsZero order reactions Easy Question 3 of 3 in Zero order reactions

$2A \rightarrow B + C$. It would be a zero order reaction when : -

A The rate of reaction is proportional to square of conc. of A
B The rate of reaction remains same at any conc. of A
C The rate remains unchanged at any conc. of B and C
D The rate of reaction doubles if conc. of B is increased to double

The answer is B.

Solution

For a zero order reaction: rate $= k[A]^0 = k$.
So the rate does not depend on the concentration of the reactant A; it remains the same at any concentration of A.
Rate proportional to $[A]^2$ would be second order. The concentrations of the products B and C do not decide the order.
So it is zero order when the rate remains the same at any concentration of A.

Concept Rate independent of reactant concentration

Zero order reactions in past papers

3 questions from this chapter have appeared across 3 exam years.