Question

A gas diffuses four times as quickly as oxygen. The molecular weight of gas is:

• A. 2
• B. 4
• C. 8
• D. 16

Answer 1

Answer: (A)

According to rate of effusion or diffusion
$\frac{r_{O_2}}{r_x}=\sqrt{\frac{M_x}{M_{O_2}}}\left[r_x=4r_{O_2}\right]$
Molecular mass of oxygen $=32$
$\frac{r_{O_2}}{4r_{O_2}}=\sqrt{\frac{M_x}{32}}$
$M_x=2$