Question

8. According to the assumption of Kinetic molecular theory, under what conditions of pressure and temperature do you most expect these assumptions to hold true? Explain.

Answer 1

Let us see the the Assumptions of kinetic energy

1.All gases are made up of large number of extremely small particles called molecules

2.The actual volume  of a molecule is negligibly small compared to the total volume occopied by the gas

3.The molecules are always moving in straight lines in all possible directions and keep on collidind with each other and also with the walls of the container.

4. The particle exert no appreciable attraction on each other and behave as perfectly elastic bodies.

5. The pressure of a gas is due to the bombardment of the gas molecules on the walls of the container.

6.Gravity has no effect on the movement of the molecules.

7.The average kinetic energy of a molecule is directly proportional to the absolute temperature.

All these assuptions may be correct under ordinary conditions of temperature and pressure. However all these assumptions are not strictly valid at high pressure and low temperature. At high pressures and low temperatures the volume of the gas is small and therefore the actual volume of the gas molecules cannot be neglected with respect to the entire volume of the gas.

Moreover, at high pressures and low temperatures,the intermolecular distance is very small and therefoe the attractive force between the particles are significant, hence the above mentioned 4th assumption cannot be ruled out.

This shows that the above mentioned 2nd and 4th assumptions are not true under high pressure and low temperature.