Thermodynamic investigation of the azeotropic system: The binary system of (water + cyclohexane)

The molar heat capacities of the azeotropic system (0.30 mol water+0.70 mol cyclohexane) were measured by an adiabatic calorimeter in temperature range of 78–320 K. The functions of the heat capacity with respect to thermodynamic temperature were established. The phase transition took place in temperature ranges of 184–190, 271–276 and 276–283 K corresponding to the solid–solid phase transition of cyclohexane, solid–liquid phase transition of water and solid–liquid phase transition of cyclohexane, respectively. The corresponding enthalpies and entropies of the phase transition were found to be 4.559 kJ mol−1, 24.510±0.065 J K−1 mol−1; 2.576 kJ mol−1, 9.454±0.041 J K−1 mol−1; and 2.040 kJ mol−1, 7.296±0.029 J K−1 mol−1, respectively. The thermodynamic functions and the excess thermodynamic functions of the azeotrope were derived based on the relationships of the thermodynamic functions.