$A$ real gas obeying Van der Waals equation will resemble an ideal gas if the:

In the van der Waals equation,which term indicates the presence of attractive forces in a gas?

The pressure $(p)$ and volume $(V)$ isotherm of a van der Waals' gas,at the temperature at which it undergoes gas to liquid transition,is correctly represented by

The relation between pressure exerted by an ideal gas $(P_{ideal})$ and observed pressure $(P_{real})$ is given by the equation
$P_{ideal} = P_{real} + \frac{an^2}{V^2}$
$(i)$ If pressure is taken in $N \ m^{-2}$,number of moles in $mol$,and volume in $m^3$,calculate the unit of $a$.
$(ii)$ What will be the unit of $a$ when pressure is in atmosphere and volume in $dm^3$?

At a given temperature $T$,gases $Ne$,$Ar$,$Xe$,and $Kr$ are found to deviate from ideal gas behaviour. Their equation of state is given as $P = \frac{RT}{V - b}$ at $T$. Here,$b$ is the van der Waals constant. Which gas will exhibit a steeper increase in the plot of $Z$ (compression factor) versus $P$?

When does the graph of $p \propto \frac{1}{V}$ not result in a straight line?