The conversion of methyl isonitrile to acetonitrile in the gas phase at $250C$

$C{H}_{3}NC(g)C{H}_{3}CN(g)$

is first order in $C{H}_{3}NC.$

In one experiment, when the initial concentration of $C{H}_{3}NC$ was $0\mathrm{.}0538M,$ the concentration of $C{H}_{3}N{C}_{\text{d}\text{r}\text{o}\text{p}\text{p}\text{e}\text{d}to}7\mathrm{.}26{10}^{-3}M$ after $422$ seconds had passed.

Based on these data, the rate constant for the reaction is

$s^{-1}$