Question

Easily liquefiable gases show larger deviations from gas laws. Comment on this statement on the basis of kinetic molecular theory.

Answer 1

• Derivation of the gas laws is based on a set of assumptions. (Ideal gas equation: PV=nRT where P= Pressure, V= Volume, T= Temperature, n= Number of moles of the ideal gas and R= Gas constant)
• Two important assumptions are:

1. The molecules of a gas are separated from each other by large distances so that the actual volume of the gas is negligible as compared to the total volume of gas.
2. The distance of separation between molecules is so large that the force of attraction or repulsion between them is negligible.

• But when gases liquefy, these two assumptions are not followed. It is found that:

1. The molecules of easily liquefiable gases have a large volume. Therefore, the assumption that volume of the gas is not negligible with respect to the volume of the container.
2. These gases are highly compressible and interact with each other resulting in larger force of attraction leading to liquification of gas. Therefore, force of attraction is not negligible.

• As the assumptions are not found to be true, the laws that were derived from these assumptions are also not followed as expected and hence larger deviation from gas laws is observed.
• Examples of easily liquefiable gases: H₂ (Hydrogen), N₂ (Nitrogen), O₂ (Oxygen)