Entropy Change and Free Energy Change in the Liquid-Vapor Phase Transition of Alkali Metals

A three-parameter generalized van der Waals equation of state has been employed to determine free energy change and entropy changein the liquid-vapor transition of fluid alkali metals in the range of temperatures from their boiling point to critical point. This equation differs from the known van der Waals equation of state by the modified expression for molecular pressure. The results yielded by the generalized van der Waals equation of state agree well with those given by Carruth and Kobayashi correlation (CK), Fish and Liemezs correlation (FL) and Watson correlation.