Excess Enthalpy and Heat Capacity for an Ethanol Water Mixture Wolfram Demonstrations Project Hvap for water is 40.7 KJ `mol^(1)` . The entropy of vaporization of water is: CHAPTER 8 Video answer for \Delta_{\text {vap }} \mathrm{H}^{\Theta} for water is +40.79 \mathrm{kJ} \mathrm{mol}^{ 1} at 1 bar and 100^{\circ} \mathrm{C}. Change in internal energy for this vapourisation under Thermodynamics Dornshuld Heating Curve