Write the van der Waals equation.

For real gases,the relation between $p$,$V$,and $T$ is given by the van der Waals equation:
$(p + \frac{an^2}{V^2})(V - nb) = nRT$
Where $a$ and $b$ are van der Waals constants,$nb$ is approximately equal to the total volume of the molecules of a gas,and $a$ is the measure of the magnitude of intermolecular attraction.
$(i)$ Arrange the following gases in the increasing order of $b$. Give reason: $O_2, CO_2, H_2, He$
$(ii)$ Arrange the following gases in the decreasing order of magnitude of $a$. Give reason: $CH_4, O_2, H_2$

For one mole of a van der Waals' gas,the compressibility factor $Z = (pV/RT)$ at a fixed volume will certainly decrease,if
[Given : $a$ and $b$ are standard parameters for van der Waals' gas]

For a gas,the deviation from ideal behavior is maximum at:

The volume of gas $A$ is twice that of gas $B$. The compressibility factor of gas $A$ is thrice that of gas $B$ at the same temperature. The ratio of the pressures of the gases for equal number of moles is:

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