The decomposition of hydrogen peroxide in dilute sodium hydroxide at $20C$

$H_2{O}_2(aq)H_{2}O(l)+\frac{1}{2}{O}_2(g)$

is first order in

$H_2{O}_2$ with a rate constant of

$1\mathrm{.}10{10}^{-3}mi{n}^{-1}.$

If the initial concentration of $H_2{O}_2$ is $0\mathrm{.}0418M,$ the concentration of $H_2{O}_2$ will be $M$ after $1519$ min have passed.