Question

Compounds ‘A’ and ‘B’ react according to the following chemical equation:

A (g) + 2 B(g) → 2C (g)

The concentration of either ‘A’ or ‘B’ was changed keeping the concentrations of one of the reactants constant and rates were measured as a function of initial concentration. Following results were obtained. Choose the correct option for the rate equations for this reaction.

(a) Rate = k [A]² [B]
(b) Rate = k [A] [B]²
(c) Rate = k [A] [B]
(d) Rate = k [A]² [B]⁰

Answer 1

(b) Rate = k [A] [B]²

From expts.l and 3, [B] = constant, [A] = doubled, rate is doubled. Hence, Rate ∝ [A].
From expts. 1 and 2, [A] = constant, [B] = doubled, rate quadrupled. Hence, Rate ∝ [B]².
Combining, Rate = k [A][B]².