The compressibility factor $(Z)$ of a gas at critical state is $(T_c = \frac{8 a}{27 R b}; p_c = \frac{a}{27 b^2}; V_c = 3 b)$.

For gases $W, X, Y$ and $Z$,the van der Waals constants are given below. Which gas has the highest critical temperature?

Gas	$a$ (atm $L^2$ mol$^{-2}$)	$b$ ($L$ mol$^{-1}$)
$W$	$4.0$	$0.027$
$X$	$8.0$	$0.030$
$Y$	$6.0$	$0.032$
$Z$	$12.0$	$0.027$

Explain the liquefaction of $CO_2$ gas using the Thomas Andrews plot,including the effects of temperature and pressure,and define the critical constants.

What are the most favourable conditions to liquefy a gas?

Which of the following statements is incorrect?

Which intermolecular force is most responsible for allowing $Xe$ gas to liquefy?