Thermodynamic functions at isobaric process of van der Waals gases

The thermodynamic functions for the van der Waals equation are investigated at isobaric process. The Gibbs free energy is expressed as the sum of the Helmholtz free energy and PV, and the volume in this case is described as t he implicit Function of the cubic equation for V in the van der Waals equat ion. Furthermore, the Gibbs free energy is given as a function of the reduc ed temperature, pressure and volume, introducing a reduced equation of stat e. Volume, enthalpy, entropy, heat capacity, thermal expansivity, and isoth ermal compressibility are given as functions of the reduced temperature, pr essure and volume, respectively. Some thermodynamic quantities are calculat ed numerically and drawn graphically. The heat capacity, thermal expansivit y, and isothermal compressibility diverge to infinity at the critical point . This suggests that a second-order phase transition may occur at the criti cal point.