Use Hess's law to prove that Delta subH = Delta vapH + Delta fusH. Homework.Study.com Delta_{vap}H^ for water is +40.49 kJ moi^ 1 at 1 bar and 100C . Change in internal energy for this vaporization under same condition is Sarthaks eConnect Largest Online Education Community Vapor Pressure Calculated and Experimental Enthalpies vap H and vap H exp of Download Table Finding Delta H using ln P vs 1 T (Hvap Lab) Solved Heat of vaporization of water at 100 degree C and Chegg.com