Question

1a- Discuss the vaporization of water in standard condition at 298 K in term of: -A exothermicity and endothermicity -Achange of entropy of the system and the surrounding - A spontaneity of the reaction. 1b- Explain how the temperature and the composition of the two phases (liquid and vapour) influence the spontaneity of the vaporization of water. Please show steps and give ample explanation. Thank you

Answer 1

Vaporization of water is an endothermic process. Heat is given to break the intermolecular bonding between the individual water molecules in liquid phase. This interaction is much weaker in the vapor phase. The more ordered arrangement of water molecules in the liquid phase gives it a lower entropy value that is less random state. In vapor phase the degree of randomness is higher and hence the entropy of the system goes up. Molecules move more freely in the vapor phase. As we increase the amount of heat supplied to the system, initially only a small fraction of molecules remain in the vapor phase as opposed to a large number of moelcules in the vapor phase. As time goes, more molecules pass on to the vapor phase and once the composition of vapor to liquid goes up, evaporation process proceeds. At the end most of the liquid water has been transformed into its vapor phase and this results in end of distillation.