The enthalpy of vaporization, (symbol ∆H vap) also known as the (latent) heat of vaporization or heat of evaporation, is the amount of energy (enthalpy) that must be added to a liquid substance, to transform a quantity of that substance into a gas.
Enthalpy of vaporization for water is 186.5 kJ mol-1.
The entropy change during vaporization is ........ kJK-1mol-1