Kinetic Theory - Result Question 2
2. Two vessels separately contain two ideal gases $A$ and $B$ at the same temperature. The pressure of A being twice that of B. Under such conditions, the density of $A$ is found to be 1.5 times the density of $B$. The ratio of molecular weight of $A$ and $B$ is :
[2015 RS]
(a) $\frac{3}{4}$
(b) 2
(c) $\frac{1}{2}$
(d) $\frac{2}{3}$
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Answer:
Correct Answer: 2. (a)
Solution:
- (a) From $PV=nRT$
$P_A=\frac{\rho_A M_A}{RT}$ and $P_B=\frac{\rho_B M_B}{RT}$
From question, $\frac{P_A}{P_B}=\frac{\rho_A}{\rho_B} \frac{M_A}{M_B}=2 \frac{M_A}{M_B}=\frac{3}{2}$
So, $\frac{M_A}{M_B}=\frac{3}{4}$
