Standard Enthalpy of Formation, \(\Delta H_{\rm f}^\circ \) Delta Extrax Diamond Heights Disposable 3G D8 Gas 10.10: Enthalpy of Fusion and Enthalpy of Vaporization Chemistry LibreTexts 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 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