Question

Ratio of rates of diffusion of $He$ and ${CH}_4$: (under identical conditions).

• A. $\frac{1}{2}$
• B. $3$
• C. $\frac{1}{3}$
• D. $2$

Answer 1

Answer: (D)

$2$

Solution:- (D) 2

According to Graham's law-

Rate of diffusion or effusion of a gas at given conditions inversely proportional to the root of molecular mass of gas.

$r\propto \frac{1}{M}$

whereas,

$r=$ rate of diffusion

$M=$ Mass of the substance

$\therefore \frac{r_{He}}{r_{C{H}_4}}=\sqrt{\frac{M_{C{H}_4}}{M_{He}}}$

$\Rightarrow \frac{r_{He}}{r_{C{H}_4}}=\sqrt{\frac{16}{4}}=\sqrt{4}=2$