For real gases the relation between p, V and T is given by c=van der Waal's equation
`(p+ (an^(2))/V^(2)) (V-nb)=nRT`
where, 'a' and 'b' are van der Waal's constanrs, 'nb' is approximately equal to the total volume of the molecules of a gas. 'a' is the measure of magnitude of intermolecular attraction.
(i) Arrange the following gases in the increasin order of 'b'. give reason.
`O_(2), CO_(2), H_(2), He`
(ii) Arrange the following gases in the decreasing order of magnitude of 'a'. Give reason.
`CH_(4), O_(2), H_(2)`

Explanation

(i) Molar volume occupied by the gas molecules `prop` size of the molecules and van der Waal's constant 'b' represents molar volume of the gas molecules Hence, value of 'd' increases in the following order
`H_(2) lt He lt O_(2) lt CO_(2)`
(ii) van der Waal's constant 'a' is the measure of magnitude of intermolar attraction. The magnitude of intermolecular attractions increases with increase in size of electron cloud in a molecule. Hence for the given gases magnitude of 'a' decreases in the following order
`CH_(4) gt O_(2) gt H_(2)`
Greater the size of electron cloud, greater is the polarisability of the molecule and greater is the dispersion forces or London forces.