Question

Under similar conditions which of the following gases will diffuse four times as fast as oxygen?

• A. $He$
• B. $N_2$
• C. $H_2$
• D. $D_2$

Answer 1

The correct option is C $H_2$

Using Graham's Law we can write:
$\frac{r_{gas}}{r_{O_2}}=\sqrt{\frac{M_{O_2}}{M_{gas}}}$
where $M=$ Molecular mass and $r=$ rate of diffusion

For the given condition,
$4=\sqrt{\frac{32}{M_{gas}}}$
$\Rightarrow 16=\frac{32}{M_{gas}}$
$\Rightarrow M_{gas}=\frac{32}{16}=2$
Hence, the gas is $H_2$.