Standard enthalpy of vapourisation ΔvapH(0) for water at 100 is 40.66 kJmol−1. The internal energy of vapourisation of water at 100 (in kJmol−1) is:
Assuming that water vapour is an ideal gas, the internal energy change (ΔU) when 1 mol of water is vapourised at 1 bar pressure and 1000C will be:
[Given molar enthalpy of vapourisation of water at 1bar and 373 K=41 kJ mol−1]
Assuming that water vapour is an ideal gas, the internal energy change (∆U) when 1 mol of water is vapourised at 1 bar pressure and 100∘ C, (given : molar enthalpy of vapourisation of water at 1 bar and 373 K = 41 kJ mol−1 and R = 8.3 J mol−1 K−1 ) will be
Assuming the water vapour is an ideal gas, the internal energy change (ΔU) in kJ when 1 mole of water is vapourised at 177∘C. (Given molar enthalpy of vapourisation of water 177∘C = 37 kJ/mol and R=253 J/molK)