Question

A $0.5\, dm^3$ flask contains gas $A$ and $1 \,dm^3$ flask contains gas $B$ at the same temperature. If density of $A = 3.0\, g\, dm^{-3}$ and that of $B = 1.5\, g\, dm^{-3}$ and the molar mass of $A=\frac{1}{2}$ of $B$, then the ratio of pressure exerted by gases is

• A. $P_A/P_B = 2$
• B. $P_A/P_B = 1$
• C. $P_A/P_B = 4$
• D. $P_A/P_B = 3$

Answer 1

Answer: (C)

$P_A/P_B = 4$

Answer 2

$P=d \frac{RT}{M}$, as const. $T,$ $\frac{P_{A}}{P_{B}}=\frac{d_{A}}{d_{B}}=\frac{M_{B}}{M_{A}}=\frac{3.0}{1.5}\times2=4$