Question

$X$ and $Y$ are two volatile liquids with molar weights of $10 \,g \,mol ^{-1}$ and $40\, g\, mol ^{-1}$ respectively. Two cotton plugs, one soaked in $X$ and the other soaked in $Y$, are simultaneously placed at the ends of a tube of length $L =24 cm$, as shown in the figure. The tube is filled with an inert gas at 1 atmosphere pressure and a temperature of $300\, K$. Vapours of $X$ and $Y$ react to form a product which is first observed at a distance $d cm$ from the plug soaked in $X$. Take $X$ and $Y$ to have equal molecular diameters and assume ideal behaviour for the inert gas and the two vapours.

The experimental value of $d$ is found to be smaller than the estimate obtained using Graham's law. This is due to

• A. larger mean free path for $X$ as compared to that of $Y$.
• B. larger mean free path for $Y$ as compared to that of $X$.
• C. increased collision frequency of $Y$ with the inert gas as compared to that of $X$ with the inert gas.
• D. increased collision frequency of $X$ with the inert gas as compared to that of $Y$ with the inert gas.

Answer 1

Answer: (D)

As the collision frequency increases then molecular speed decreases than the expected.