Question

A first order reaction takes 40 minutes for 30% completion. Calculate the half-life of reaction.

Options

• 77.7 min

• 23.1 min

• 42.7 min

• 57.8 min

Answer 1

77.7 min

Explanation:

k = `2.303/"t" log_10  (["A"]_0)/(["A"]_"t")`

= `2.303/40 log_10  100/70`

= 0.05757 log₁₀ 1.428

= 0.05757 × 0.1547

= 0.0089 min⁻¹

t_1/2 = `0.693/0.0089` = 77.865 min