Question

A certain volume of argon gas(mol wt.40) requires 45 $s$ to effuse through a hole at a certain pressure an temperature. The same volume of another gas of unknown weight requires 60 $s$ to pass through the same hole under the same conditions of temperature and pressure. The molecular weight of the gas is:

• A. 53
• B. 35
• C. 71
• D. 120

Answer 1

The correct option is C 71

As we know,

$r\alpha$ $\frac{1}{\sqrt{M}}$

$\frac{t_2}{t_1}=\sqrt{\frac{M_2}{M_1}}$

$\frac{60}{45}=\sqrt{\frac{X}{40}}$
$\Rightarrow$ $\sqrt{\frac{X}{40}}=\frac{4}{3}$
$\Rightarrow$ $\sqrt{\frac{X}{40}}=\frac{16}{9}$

$X=71.11\approx 71$

Hence, the correct option is $\text{C}$