Question

Two separate bulbs contain ideal gases A and B. The density of gas A is twice that of gas B. The molecular mass of A is half that of gas B. The two gases are at the same temperature. The ratio of the pressure of A to that of gas B is

• A. 2
• B. 1/2
• C. 4
• D. 1/4

Answer 1

The correct option is C 4

$d_a=2d_b;2M_a=M_b$
PV = nRT = $\frac{m}{M}$RT; P = $\frac{m}{M}$.$\frac{RT}{M}$ = $\frac{dRT}{M}$
$\frac{P_a}{P_b}=\frac{d_a}{d_b}\frac{M_b}{M_a}=\frac{2d_b}{d_b}\times \frac{2M_a}{M_a}=4$