Question

A first order reaction is 25% completed in 40 minutes. What is the rate constant k tor the reaction?

Options

• `(2.303 xx log 1.33)/40`

• `2.303 xx log  4/3`

• `(2.303 xx log 4)/(40 xx 3)`

• `2.303/40 xx log  1/4`

Answer 1

`(2.303 xx log 1.33)/40`

Explanation:

Given,

Time (t) = 40 min

a = 100

(a - x) = 100 - 25 = 75

First order reaction,

Rate (k) = `2.303/"t" log  ("a"/("a - x"))`

`= (2.303 xx log 1.33)/40`