Question

A $0.5$ $d{m}^3$ flask contains gas $A$ and 1 $d{m}^3$ flask contains gas $B$ at the same temperature. If density of $A=3g/d{m}^3$ and that of $B=1.5g/d{m}^3$ and the molar mass of $A=1/2$ of $B$, the ratio of pressure exerted by gases is:

• A. $\frac{P_A}{P_B}=2$
• B. $\frac{P_A}{P_B}=1$
• C. $\frac{P_A}{P_B}=4$
• D. $\frac{P_A}{P_B}=3$

Answer 1

The correct option is C $\frac{P_A}{P_B}=4$

The ideal gas equation is:

$PM=DRT$

At constant temperature:

$\frac{P_A}{P_B}=\frac{D_A{M}_B}{M_A{D}_B}$

$=\frac{3\times M_B}{1.5\times 0.5M_B}=4$

Hence, the ratio of the pressure exerted by the gases A and B is $4:1$.

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