States of Matter · Question 4

Two cylinders, both fitted with frictionless pistons, are filled with mixtures of He and Ar gases. In the first cylinder, the masses of He and Ar are m1 and m2, respectively. In the second cylinder, the masses of He and Ar are m2 and m1, respectively. The molar mass of Ar is 10 times the molar mass of He. The external pressure applied by the piston on the first cylinder needs to be 5 times that on the second cylinder so that the volume of the gas mixtures in both the cylinders are equal at the same temperature. Assuming He and Ar behave like ideal gases, the value of (m1/m2) is .

Molar volume (Vm) of a van der Waals gas can be calculated by expressing the van der Waals equation as a cubic equation with Vm as the variable. The ratio (in mol dm-3) of the coefficient of Vm2 to the coefficient of Vm for a gas having van der Waals constants a = 6.0 dm6 atm mol-2 and b = 0.060 dm3 mol-1 at 300 K and 300 atm is . Use: Universal gas constant (R) = 0.082 dm3 atm mol-1 K-1

The correct statement(s) about intermolecular forces is(are)

1. The potential energy between two point charges approaches zero more rapidly than the potential energy between a point dipole and a point charge as the distance between them approaches infinity.
2. The average potential energy of two rotating polar molecules that are separated by a distance r has 1/r3 dependence.
3. The dipole-induced dipole average interaction energy is independent of temperature.
4. Nonpolar molecules attract one another even though neither has a permanent dipole moment.