At what pressure does $SO_2$ gas liquefy at room temperature?

What is critical temperature $(T_{C})$?

Isotherms of carbon dioxide gas are shown in the figure. Mark a path for changing gas into liquid such that only one phase (i.e.,either a gas or a liquid) exists at any time during the change. Explain how the temperature,volume,and pressure should be changed to carry out this process.

What are the most favourable conditions to liquefy a gas?

Gases possess characteristic critical temperature which depends upon the magnitude of intermolecular forces between the particles. Following are the critical temperatures of some gases:

$Gases$	$Critical \ temperature \ in \ Kelvin$
$P$	$33.2$
$Q$	$5.3$
$R$	$154.3$
$S$	$126$

From the above data,what would be the order of liquefaction of these gases? Start writing the order from the gas liquefying first.

Assertion : Gases do not liquefy above their critical temperature,even on applying high pressure.
Reason : Above critical temperature,the molecular speed is high and intermolecular attractions cannot hold the molecules together because they escape because of high speed.