The $Van \text{ der } Waals$ equation explains the behaviour of

The compressibility factor $(Z)$ of a gas is less than unity at $STP$. Therefore:

The compressibility factor for a real gas at high pressure is $:$

For real gases,the relation between $P$,$V$ and $T$ is given by the van der Waals equation,$(P + \frac{an^2}{V^2})(V - nb) = nRT$. For the following gases $CH_4, CO_2, O_2, H_2$,which gas will have $(i)$ highest value of $'a'$ $(ii)$ lowest value of $'b'$?

Under which one of the following conditions do real gases approach the ideal gas behaviour?

Gases deviate from ideal gas behavior because the molecules $...$