Real gases show deviation from ideal gas behavior because the molecules .............

What is the unit of the Van der Waals constant $a$?

The van der Waals equation is valid for $......$.

What is the correction term in the pressure for real gas in comparison to the ideal gas?

Excluded volume $(v)$ per molecule is related to the van der Waals constant $'b'$ in the following way:

For $1 \ mol$ of gas,the plot of $pV$ vs $p$ is shown below. $p$ is the pressure and $V$ is the volume of the gas. What is the value of compressibility factor at point $A$?