Question

23.Assertion: The value of compressibility factor Z, is lesser than 1 at low

pressure for a real gas.

Reason: This is because at low pressure, the effective volume occupied

by the real gas molecules, cannot be neglected.​

Answer 1

Explanation:

At low pressure conditions, the compressibility factor for one mole of gas is given by z=1−

z(RT)

2

ap

Proof-

Vander waals equation-

(P+

V

2

a

)(VP)=RT (for 1 mole of gas)

Low pressure ⟹

V

2

a

is not negligible, Neglect b.

(P+

V

2

a

)(V)=RT

PV+

V

a

=RT

Divide by RT on both sides,

RT

PV

+

V(RT)

a

=1

z=1−

z(RT)

2

a

We know z=

RT

PV