Question

The density of a gas A is thrice that of a gas B at the same temperature. The molecular weight of gas B is twice that of A. What will be the ratio of the pressures acting on B and A ?

• A. $\frac{1}{4}$
• B. $\frac{7}{8}$
• C. $\frac{2}{5}$
• D. $\frac{1}{6}$

Answer 1

The correct option is D $\frac{1}{6}$

$d=\frac{PM}{RT}$
Let density of gas B be d
Then, density of gas A is 3d
Let molecular weight of A be M
then molecular weight of B is 2M
$\frac{P_B}{P_A}=\frac{d_B}{d_A}\times \frac{M_A}{M_B}=\frac{d}{3d}\times \frac{M}{2M}=\frac{1}{6}$