Equation of State

An Equation of State describes the equilibrium conditions of a system in terms of values of (p,v,T) that generate the equilibrium surface of state for the substance. For an Ideal Gas the equation of state has the form: pv = RT, where R is the Universal Gas Constant ( 8.314 J/ (mol.K))

This surface is shown opposite as well as projections of paths in the surface onto the (p,T), (p,v) and (T,v) planes.These paths represent equilibrium processes for constant v, T, and p, respectively.

Diagram from: Howell & Buckius, "Fundamentals of
Engineering Thermodynamics," McGraw Hill (1987)