The critical temperature of $O_2$ is $154.3 \ K$ and the critical temperature of $N_2$ is $126.0 \ K$. Which gas will liquefy first during the liquefaction of air?

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

$Gases$	$H_2$	$He$	$O_2$	$N_2$
$Critical \ temperature \ (K)$	$33.2$	$5.3$	$154.3$	$126$

From the above data,what would be the decreasing order of liquefaction of these gases?

Critical temperature for carbon dioxide and methane are $31.1^{\circ} C$ and $-81.9^{\circ} C$ respectively. Which of these has stronger intermolecular forces and why?

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.

The statement that is $NOT$ correct is

Explain the liquefaction of real gases and permanent gases.