Standard Enthalpy of Formation, \(\Delta H_{\rm f}^\circ \) 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 The difference between `Delta`H and `Delta`U at constant volume is equal to A) b) ln((p2) (p1)) = ( Hvap) (R)((1) (T1) ( Solved Heat, q, is energy transferred between a system and Chegg.com Enthalpy of vaporization Wikipedia