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?

Which set of conditions represents the easiest way to liquefy a gas?

The statement that is $NOT$ correct is

Isotherms of carbon dioxide at various temperatures are represented in the figure. Answer the following questions based on this figure.
$(i)$ In which state will $CO_2$ exist between the points $a$ and $b$ at temperature $T_1$?
$(ii)$ At what point will $CO_2$ start liquefying when temperature is $T_1$?
$(iii)$ At what point will $CO_2$ be completely liquefied when temperature is $T_2$?
$(iv)$ Will condensation take place when the temperature is $T_3$?
$(v)$ What portion of the isotherm at $T_1$ represents liquid and gaseous $CO_2$ at equilibrium?

Explain the relationship between the fluid state,liquid-gas state,critical temperature,and the vapour form of substances.

Which of the following conditions is most favorable for the liquefaction of a gas?