Question

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

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

Answer 1

The correct option is B $H_2$

By Graham's Law we know that:
$\frac{r_{gas}}{r_{O_2}}=\sqrt{\frac{M_{O_2}}{M_{gas}}}$
where M = Molecular mass and r = rate of diffusion
$4=\sqrt{\frac{32}{M_{gas}}}\text{or}16=\frac{32}{M_{gas}}$
$\text{or}{M}_{gas}=\frac{32}{16}=2,i.e.,H_2$