4.5 One mole of superheated water at 110 °C and at 1 atm is evaporated to steam at the same temperature and pressure. Calculate the change in entropy given that:

(i) In the pressure range 1 atm to 1.4 atm the entropy of liquid water at 110 °C can be considered constant.

(ii) At 110 °C liquid water and steam are in equilibrium at a pressure of 1.4 atm, and the latent heat of evaporation under these conditions is 4 × 104 J/mol.
(iii) In the pressure range 1 atm to 1.4 atm water vapour at 110 °C behaves as a perfect gas.
Calculate the error introduced by the last assumption if in the range 1 atm to 1.4 atm and at 110 °C one has, for one mole of steam,