Latent Heat of Vaporization Delta Hvap of Water calculated by corresponding states correlation in a one cell excel formula Chem Eng Musings Standard enthalpy of vapourisation `Delta_("vap")H^( )` for water at `100^@C` is `40.66 kJ mol^( 1)`. The internal energy of vapourisation of water at `100^@C` (in kJ `mol^( 1)`) is (Assume water vapour to behave like Vapor Pressure Standard Enthalpy of Formation, \(\Delta H_{\rm f}^\circ \) DeltaH` (vap) for water is `40.7 kJ mol^( 1)`. The entropy of vapourisation of water is