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

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 : At critical temperature,liquid passes into gaseous state imperceptibly and continuously.
Reason : The density of liquid and gaseous phase is equal at critical temperature.

Which are the most favorable conditions for the liquefaction of a gas?

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$^{-1}$)
$W$	$4.0$	$0.027$
$X$	$8.0$	$0.030$
$Y$	$6.0$	$0.032$
$Z$	$12.0$	$0.027$

The temperature and pressure at which ice,liquid water,and water vapour can exist together are: