Answer
$9.35\times 10^{-24}$ $kg.m.s^{-1}$
Work Step by Step
The relation between the kinetic energy $(K)$ and momentum $(P)$ of an electron is expressed by the equation
$K=\frac{P^{2}}{2m} $, in which $m$ is the mass of the electron.
$\therefore P=\sqrt {2mK}$
Given, $K=300$ $eV$$=(1.6\times 10^{-19}\times 300)$ $J$$=4.8\times 10^{-17}$ $J$,
$m=9.1\times 10^{-31}$ $kg$
Therefore, $P=\sqrt {2\times 9.1\times 10^{-31}\times 4.8\times 10^{-17}}$ $kg.m.s^{-1}$
or, $P\approx 9.35\times 10^{-24}$ $kg.m.s^{-1}$
$\therefore$ The momentum of the electron is $9.35\times 10^{-24}$ $kg.m.s^{-1}$
