Question

Two non-reactive monoatomic ideal gases have their atomic masses in the ratio $2 : 3$. The ratio of their partial pressures, when enclosed in a vessel kept at a constant temperature, is $4 : 3$. The ratio of their densities is

• A. 1:04
• B. 1:02
• C. 6:09
• D. 8:09

Answer 1

Answer: (D)

8:09

Answer 2

$PV = nRT =\frac{ m }{ M } RT$
$\Rightarrow PM =\rho RT$
$\frac{\rho_{1}}{\rho_{2}}=\frac{ P _{1} M _{1}}{ P _{2} M _{2}}$
$=\left(\frac{ P _{1}}{ P _{2}}\right) \times\left(\frac{ M _{1}}{ M _{2}}\right)$
$=\frac{4}{3} \times \frac{2}{3}=\frac{8}{9}$
Here $\rho_{1}$ and $\rho_{2}$ are the densities of gases in the vessel containing the mixture.