Using Excess Functions to Simulate Vapour Pressure in Binary Non-Electrolyte Solutions

Abstract

The paper considers simulating thermodynamic properties of completely miscible binary non-electrolyte solutions characterised by a positive deviation from ideality due to association concerning one of the solution components in general. We used a cluster-based mathematical model. The paper provides a cluster model equation to describe concentration dependences of vapor pressure over the solution as functions of the liquid phase composition. The model equation parameters are the expected value of associate distribution in the standard state and the variance of associates. We present a formalised method for simulating vapor pressure using concentration dependences of excess molar characteristics of the mixture as functions of the liquid phase composition. We derived concentration dependences of vapour pressure for binary solutions of alcohols in haloalkanes directly from the experimental data and analytically from the excess molar enthalpy and excess molar volume. These results, though derived by different methods, agree well with each other and appropriately describe vapor pressure concentration dependences as functions of the liquid phase composition. We demonstrate that varying cluster model equation parameters in a temperature range will successfully match patterns of association found in systems prone to hydrogen bond formation