Physical Chemistry Real gases Equation of State(eos) The van der Waals and R-K equations are cubic equations of state a cubic algebraic equations al ways has three roots e above the critical temperature T two of the roots are complex numbers, one will be a real number At the critical temperature t three equal real roots Below the critical temperature To three unequal real roots a cubic equation of states isotherm in the two-phase region below Te will resemble the dotted line in Fig. 8.3Equation of State (eos) The van der Waals and R-K equations are cubic equations of state. Physical Chemistry Real Gases A cubic algebraic equations always has three roots. Above the critical temperature Tc , two of the roots are complex numbers, one will be a real number. At the critical temperature Tc , three equal real roots. Below the critical temperature Tc , three unequal real roots. A cubic equation of states isotherm in the two-phase region below Tc will resemble the dotted line in Fig. 8.3