Question

For a first order reaction A → products, the rate
of reaction at (A) = 0.2 M is 1x 10-2 mol L-lmin-1.
The half life period for the reaction is -
(1) 832 min.
(2) 440 s
(3) 416 min.
(4) 14 min.​

Answer 1

For a first order reaction A → products, the rateof reaction at (A) = 0.2 M is 1x 10-2 mol L-lmin-1. The half life period for the reaction is -

(1) 832 min.

(2) 440 s

(3) 416 min.

(4) 14 min.

answer : option (4) 14 min

explanation : for first order reaction, half life doesn't depend on concentration of reactants. it only depends on rate constant. i.e., t = ln2/k

given, rate of reaction at [A] = 0.2 K is 1 × 10^-2 mol.L-¹min-¹

from reaction, r = k[A]

or, 1 × 10^-2 = k × 0.2

or, k = 5 × 10^-2 min-¹

now, half life period , t = ln2/(5 × 10^-2)

= 20ln2

= 13.8629436 ≈ 14min