Question

If the rate constant for a first-order reaction is k, the time (t) required for the completion of 99% of the reaction is given by:

Options

• t = `0.693/"k"`

• t = `6.909/"k"`

• t = `4.606/"k"`

• t = `2.303/"k"`

Answer 1

t = `bb(4.606/"k")`

Explanation:

For a first-order reaction,

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

for 99% completion of the reaction,

t = `2.303/"k" log  100/(100 - 99)`

t = `2.303/"k" log 10^2`

t = `4.606/"k"`