Question

The density of gas $A$ is twice that to $B$ at the same temperature the molecular weight of gas $B$ is twice that of $A$. The ratio of pressure of gas $A$ and $B$ will be:

• A. 1 : 6
• B. 1 : 1
• C. 4 : 1
• D. 1 : 4

Answer 1

The correct option is C 4 : 1

$d_A=2d_B$; $2M_A=M_B$; $PM=dRT$
$=\frac{P_A}{P_B}\times \frac{M_A}{M_B}=\frac{d_A}{d_B}\times \frac{RT}{RT}$
$=\frac{P_A}{P_B}\times \frac{1}{2}=2$
$\frac{P_A}{P_B}=\frac{4}{1}$