Application of a New Statistical Mechanical Model for Calculating Kirkwood Factors in Alkanol−Heptane Mixtures

Abstract

A recently developed statistical mechanical model for predicting Kirkwood factors in self-associating molecular liquids and their mixtures with nonassociating components has been applied for the simultaneous description of the Kirkwood correlation factor, gK, and the molar enthalpy of mixing, Hm(E), as a function of the composition in alkanol-heptane mixtures. Most of the molecular parameters involved in the theory have been fixed by independent quantum mechanical ab initio calculations of associated molecular clusters. The model is also able to predict other thermodynamic mixture properties such as the enthalpy of mixing. Experimental results of nine alcohol-heptane mixtures taken from the literature have been used to test the new model. The Kirkwood correlation factor gK and the molar enthalpy of mixing Hm(E) can be described simultaneously with an excellent agreement with experimental data covering the whole range of mole fraction, including temperature dependence. Two parameters have been adjusted freely for each system. A third parameter for the nonspecific intermolecular dispersion interactions has been adjusted within a limited range of possible values given by physical arguments. The successful application of the model opens a new way to a more reliable understanding of structures and equilibrium properties of such liquid systems.