“The equation connecting the pressure, the volume & absolute temperature of a substance is called the Equation of State of the system”.
Thus for a gas forming the system, these three quantities are not independent & connected by a relationship, i.e.
f( P, V, T ) = 0
PV = RT
where R = universal gas constant
= 8.314 Joule /gm
= 8314 J/Kg mol – K
V = molar volume
|Fig. Vanderwall’s equation of state.|
For an equation of state, it should be noted that:
2. An equation of state is not a theoretical deduction from thermodynamics but is an experimental addition to it.
3. The equation of state is not applicable to systems not in thermodynamic equilibrium.