The Honig–Flory–Huggins combinatorial entropy correction—is it valid for aqueous solutions?

Abstract

A number of assumptions used in the derivation of the combinatorial entropy term of Honig–Flory–Huggins are shown not to be valid for the case of dilute solutions in water: these include (a) only combinatorial entropy need be considered, (b) the solution configuration is random, and (c) random distribution of molecular segments in the solution lattice. Accordingly, the combinatorial term as calculated by Honig–Flory–Huggins is not appropriate for aqueous solutions, and is particularly inappropriate for dilute solutions in water. It is suggested that the use of the Honig–Flory–Huggins combinatorial entropy term to ‘correct’ observed thermodynamic parameters for solvation of solutes in water be abandoned.