Question

For real gases the relation between p, V and T is given by
van der Waals equation in which ‘a’ and ‘b’ are van der Waals constants, ‘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 increasing order of
‘b’. Give reason. O2,CO2, H2, He
(ii) Arrange the following gases in the decreasing order of
magnitude of ‘a’. Give reason.
CH4,O2, H2

Answer 1

Answer:

See below.

Explanation:

a) As given, the constant 'b' is equal to the volume of a single molecule ( considered as a sphere ).

We are given the gases,

$O_{2},CO_{2},H_{2},He$

The above molecules will look like two spheres merged into each other.

The size of H atom is the smallest. The size of C is greater than that of O atom. So, logically, the size of CO2 will be greater than the size of O2. He will have the smallest volume as it is monoatomic.

So, the order is,

$He <H_{2} <O_{2} <CO_{2}$

b) The H-H bond has the highest enthalpy. Then comes O2 and CH4.

$H_{2} >O_{2} >CH_{4}$