The ratio of rates of diffusion of helium (He) to hydrogen $\left(\mathrm{H}_2\right)$.
The ratio of rates of diffusion of helium (He) to hydrogen $\left(\mathrm{H}_2\right)$.
$\sqrt{2}: 1$
$1: \sqrt{2}$
$1: 4$
$1: 1.229$
Solution
Molecular mass of $\mathrm{H}_2=2$
Molecular mass of $\mathrm{He}=4$
$
\begin{aligned}
\frac{\text { Rate of diffusion of } \mathrm{He}}{\text { Rate of diffusion of } \mathrm{H}_2} & =\sqrt{\frac{\text { Molecular mass of } \mathrm{H}_2}{\text { Molecular mass of } \mathrm{He}}} \\
& =\sqrt{\frac{2}{4}}=\frac{1}{\sqrt{2}} \\
\therefore \quad r_{\mathrm{He}}: r_{\mathrm{H}_2} & =1: \sqrt{2}
\end{aligned}
$