Question

Please do not use Z in your answer as the main answer, only use it to explain.

When the pressure calculated by the ideal gas law is larger than the pressure calculated by VdW for a real gas, are the gas particles in the repulsive region or the attractive region?

When the pressure calculated by the ideal gas law is smaller than the pressure calculated by VdW for a real gas, are the gas particles in the repulsive region or the attractive region?

When the pressure calculated by the ideal gas law is equal to the pressure calculated by VdW for a real gas, are the gas particles in the repulsive region or the attractive region?

When the volume calculated by the ideal gas law is larger than the volume calculated by VdW for a real gas, are the gas particles in the repulsive region or the attractive region?

Answer 1

Not all gases follow ideal behaviour. There are internuclear forces of attraction which make gases deviate from ideal behaviour.

Pressure is calculated as the net force exerted by gas on an area(wall of the container). Now real gases have inter nuclear force of attraction which reduce this net force exerted on wall of container. Hence less pressure is observed for a real gases than ideal gases and we say that gases are in attractive region.

Similarly opposite is true when gases are in repulsive region. Such real gases exert more pressure on the wall of container than real gases.

real gases behave similarly to ideal gas when the internuclear forces are negligible(whether attractive or repulsive).Hence pressure calculated will be same.

ideal gases assume that the volume occupied by atoms is negligible but real gases have actual volume occupied by atoms and this difference is called volume correction factor 'b'. this factor depends on size of the atom and not on forces of interaction(attractive or repulsive).