Vapor Pressure 3 Ways to Calculate Vapor Pressure wikiHow The difference between `Delta`H and `Delta`U at constant volume is equal to Chapter 10: Thermochemistry Lecture Note Edubirdie Delta 8 THC Disposable Vape Pineapple Express 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