Question

For a reaction, A + B ¾® Products, the rate is first order with respect to A and second order with respect to B. If 1.0 mole each of A and B are introduced into a 1 litre vessel and the initial rate were 1.0 × 10^–2mollitre^–1 sec^–1. The rate

(inmollitre^–1 sec^–1) when half of the reactants have been used-

• A. 1.25 × 10^–3
• B. 1.2 × 10^–2
• C. 2.5 × 10^–4
• D. None of these

Answer 1

Answer: (A)

1.25 × 10^–3

Answer 2

order w.r.t. A = 1

order w.r.t. B = 2

\ r = K [A] × [B]²

when A and B are consumed 50%,

r¢ = K × $\left\lbrack \frac{A}{2} \right\rbrack$× $\left\lbrack \frac{B}{2} \right\rbrack^{2}$= r × $\frac{1}{8}$ = (1.0 × 10^–2) × $\frac{1}{8}$

= 1.25 × 10^–3