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 Re)
Solution:
We know $M = \frac{\rho RT}{P}$. Given $T_A = T_B$, $P_A = 2P_B$, and $\rho_A = 1.5\rho_B$. The ratio of molecular weights is $\frac{M_A}{M_B} = (\frac{\rho_A}{\rho_B}) \times (\frac{P_B}{P_A}) = 1.5 \times \frac{1}{2} = 0.75 = \frac{3}{4}$.
Leave a Reply