18.0 g of water completely vaporises at 100∘C and 1 bar pressure and the enthalpy change in the process is 40.79 kJ mol−1. What will be the enthalpy change for vaporising two moles of water under the same conditions? What is the standard enthalpy of vaporisation for water?
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]