Industrial & Engineering Chemistry Research, Vol.42, No.25, 6290-6293, 2003
Chemical meaning of the standard free energy of transfer. 2. Use of van der Waals' equation of state to evaluate the enthalpic and entropic contributions of free volume and attractive forces to chemical potentials
In a previous paper we derived an equation for the chemical potential of a nonideal, infinitely dilute solute in a van der Waals fluid. From this we also explored the change in the Gibbs energy of transfer of a solute between two van der Waals fluids and explored the effects of using different standard states on the interpretation of that Gibbs energy. In this paper, we extend that treatment by dissecting the equation for the chemical potential of an infinitely dilute solute in a van der Waals fluid to reveal the enthalpic and entropic origins of each term. We also provide a physical interpretation of each term based on its enthalpic and entropic contributions to the overall chemical potential. We conclude the paper with an exploration of the phenomenon of enthalpy/entropy compensation, using the van der Waals equation of state to derive a condition under which enthalpy/entropy compensation must be observed.