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 Explain the state function 'enthalpy, H'. What is the relationship between `DeltaU and DeltaH`? Calculated and Experimental Enthalpies vap H and vap H exp of Download Table Enthalpie standard de vap de l'ethanol