Question

What are critical constants Tc, Pc and Vc. Give their relationships with van der waal’s constants ‘a’ and ‘b’.

Answer 1

Tc= Temperature at and above which the vapour state can not be further liquified.

Pc= Pressure of gas in its critical state

Vc= Volume of gas in its critical state.

relation with the van der waals constants -

Tc = 8a / 27 Rb

Vc = 3b

Pc = a / 27 b^2

Answer 2

Answer :

Critical temperature : It is defined as the temperature of a gas in its critical state that means above which it cannot be liquefied by pressure.

The formula of Critical temperature is,

$T_c=\frac{8a}{27Rb}$

where,

$T_c$ = Critical temperature

'a' and 'b' are the vander waals constant

R = universal gas constant

Critical pressure : It is defined as the pressure of a gas in its critical state that means the pressure required to liquefy a gas at its critical temperature.

The formula of Critical pressure is,

$P_c=\frac{1}{27}\frac{a}{b^2}$

where,

$P_c$ = Critical pressure

'a' and 'b' are the vander waals constant

R = universal gas constant

Critical volume : It is defined as the volume of one mole of a gas in its critical state that means the volume liquefied at critical temperature.

The formula of Critical volume is,

$V_c=3b$

where,

$V_c$ = Critical volume

'b' is the vander waals constant