Low-temperature heat capacity of the azeotropic mixture composed of water+ethanol+benzene

Abstract

Molar heat capacity of the azeotropic mixture composed of water, ethanol, and benzene was measured by an adiabatic calorimeter from 80 to 320 K. The glass transition and phase transitions of the mixture were determined based on the curve of the heat capacity with respect to temperature. The glass transition occurred at 102.850 K. The phase transitions took place in temperature ranges 140–155 K and 265–280 K corresponding to the solid–liquid phase transitions of ethanol, water and benzene, respectively. The corresponding enthalpies and entropies of the phase transition were calculated to be 0.4157 kJ mol −1, 2.824 J K −1 mol −1; 1.293 kJ mol −1, 4.692 J K −1 mol −1; 4.876 kJ mol −1, 17.67 J K −1 mol −1; respectively. The thermodynamic functions and the excess thermodynamic functions of the mixture relative to temperature 298.15 K were derived based on the relationships of the thermodynamic functions and the function of the measured heat capacity with respect to temperature.