Phase Equilibria for a Pure Hydrocarbon

The relations which permit us to express equilibria utilize the Gibbs free energy, to which we will give the symbol G and which will be called simply free energy for the rest of this chapter. This thermodynamic quantity is expressed as a function of enthalpy and entropy. This is not to be confused with the Helmholtz free energy which we will note sF (L j (j, ) 

G = Gibbs molar free energy S = molar entropy F = Helmholtz free molar energy H = molar enthalpy U = molar internal energy 

Chapter 4. METHODS FOR THE CALCULATION OF HYDROCARBON PHYSICAL PROPERTIES 149 

At the triple point, the free energies of each phase are equal  

The liquid -vapor equilibria, along the vaporization curve is expressed as  

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