Physicochemical Perturbations of Phase Equilibriums

TL;DR

This paper develops a thermodynamic and statistical mechanics-based model to analyze how perturbations affect phase equilibrium, linking enthalpy variations to vapor pressures and other surface phenomena.

Contribution

It introduces a unified method to study various phase and surface phenomena through enthalpy variations induced by perturbations.

Findings

Provides relations between enthalpy changes and osmotic pressures.

Establishes connections between enthalpy variations and surface curvature.

Offers a physical interpretation of enthalpy change in phase perturbations.

Abstract

The alternative approach to the displacement of gas/liquid equilibrium is developed on the basis of the Clapeyron equation. The phase transition in the system with well-established properties is taken as a reference process to search for the parameters of phase transition in the perturbed equilibrium system. The main equation, derived in the framework of both classical thermodynamics and statistical mechanics, establishes a correlation between variations of enthalpies of evaporation, \Delta (\Delta H), which is induced by perturbations, and the equilibrium vapor pressures. The dissolution of a solute, changing the surface shape, and the effect of the external field of adsorbents are considered as the perturbing actions on the liquid phase. The model provides the unified method for studying (1) solutions, (2) membrane separations (3) surface phenomena, and (4) effect of the adsorption field; it leads to the useful relations between \Delta (\Delta H), on the one hand, and the osmotic pressures, the Donnan potential, the surface curvature, and the pore structure, on the other hand. The value of \Delta(\Delta H) has a clear physical meaning and gives a new insight into our understanding of the apparently different phenomena. The model is applicable if the change between entropies of the comparable gas phases is far more than the difference between entropies of the liquid phases.