Question

A reaction has a half-life of 1 min. The time required for 99.9% completion of the reaction is ______ min.
(Round off to the nearest integer).
[Use: In 2 = 0.69; In 10 = 2.3]

Options

• 10

• 80

• 30

• 20

Answer 1

A reaction has a half-life of 1 min. The time required for 99.9% completion of the reaction is 10 min.

Explanation:

This question is incomplete, order is not given. If we consider, the given reaction to be first order, then

`"t"_(1//2) = (ln 2)/"k" => "k"` = ln 2

`therefore "t" = 1/"k" ln  100/(100 - 99.9) => "t" = 1/(ln 2) ln 10^3`

`=> "t" = (1 xx 3 xx ln 10)/(ln 2) = (3 xx 2.3)/0.69` = 10 min