X and Y are two volatile liquids with molar weights of `10g mol^(-1) and 40g mol^(-1)` respectively. Two cotton plugs, one soaked in X and the other soaked in Y, are simultaneously placed at the ends of the tube of length L=24cm, 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 from the plug soaked in X. Take X and Y to have equal molecular diameters and assume ideal behavior for the inert gas and the two vapours.

The value of d in cm (shown in the figure), as estimated from Graham’s law, is:

Options

A. larger mean for path for X as compared of 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 as compared to that of Y with the inert gas.

Answer

D

Explanation

Collisions frequency is the measure of molecular collisions taking place per second per unit volume of the gas. As the collision frequnecy increases. The distance covered by the molecules becomes less than the expected value. In this case, the molecules of X being lighter result in more collisions with the inert gas molecules as compared to molecules of Y. As a result, the experimental values of d is found to be smaller than what is estimated according to Graham's Law.