question_answer

Answer the following questions : (a) A vessel with a movable piston maintained at a constant temperature by a thermostat contains a certain amount of liquid in equilibrium with its vapour. Does this vapour obey Boyle's law? In other words, what happens when the volume of vapour is decreased? Does the vapour pressure increase? (b) What is meant by 'superheated water' and 'super cooled vapour'? Do these states of water lie on its P-V-T surface? Give some practical applications of these states of water.

Answer:

                (a) No, the vapour in equilibrium with its liquid does not obey Boyle's law. When the volume of the vapour is decreased by applying pressure, some of the vapours condense into liquid, maintaining the same pressure of the vapour at the given temperature i.e., vapour pressure does not increase when the volume of vapours is decreased. (b) Superheated water. Water in liquid phase having temperature above the boiling point of water at the given pressure is called superheated water. It is highly unstable  stage. Super cooled vapour. Water in vapour phase having temperature below its boiling point at the given pressure is called super cooled vapour. It is also highly unstable stage. As the above states of water are not equilibrium states, so they do not lie on P-V-T surface of water. Applications. These unstable states of water are used in bubble chamber and cloud chamber for detecting high speed charged particles.