An ideal gas cannot be liquefied because ......

Gases possess characteristic critical temperature which depends upon the magnitude of intermolecular forces between the gas particles. Critical temperatures of ammonia and carbon dioxide are $405.5 \ K$ and $304.10 \ K$ respectively. Which of these gases will liquefy first when you start cooling from $500 \ K$ to their critical temperature?

$A$ gas can be liquefied:

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?

Which are the most favorable conditions for the liquefaction of 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.