Excess integral molar entropy

Similarly, excess integral molar entropy and enthalpy of solution may be written... 

Using data given in the previous example, calculate the values of the excess partial molar free energy of zinc and cadmium, excess integral molar free energy of solution, and excess integral molar entropy of solution at 527°C (800 K) for the equiatomic Zn-Cd solution. 

Since Zn-Cd solution exhibits regular behaviour, the excess integral molar entropy of solution is zero. 

In the general case, the integral molar entropy of adsorption is not equal to the mean differential entropy of adsorption over the range of surface excess concentration from 0 to r, because of the extra term of the right-hand side of Equation (2.67). 

The principles of phase equilibrium do not apply to excess adsorption variables at high pressure where the excess adsorption passes throu a maximum. Under these conditions, the pressure is no longer a single-valued function of excess adsorption so that n cannot serve as an independent variable for the determination of partial molar quantities such as activity coefficients. Additional complications which arise at high pressure are (1) the selectivity for excess adsorption (S12 = (nf/j/i)/(n2/y2)) approaches infinity as nj — 0 and (2) the differential enthalpy of the ith component has a singularity at the pressure corresponding to maximum nf. For excess variables, the diffierential functions are undefined but the integral functions for enthalpy and entropy are smooth and well-behaved (1). 

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