A liquid is in equilibrium with its vapour in a sealed container at a fixed temperature. The volume of the container is suddenly increased.
a. what is the initial effect of the change on vapour pressure?
b. How do rates of evaporation and condensation change initially?
c. What happens when equilibrium is restored finally and what will be the final vapour pressure?

Explanation

(a) Intially, the vapour pressure will decrease because the same account of vapour are now distributed in larger space.
(b) The rate of evaporation remains constant at constant temperature in a closed vessel 9discussed in unit 5 under vapur pressure. ). However, the rate of condensation will be low initially because there are fever molecules per unit volume in the vapour phase and hence the number ofcollisions per unit time with the liquid surface decreases.
(c ) When equilibriumis restored , rate of evaporation = rate of consensation . The final valour pressure will be same as it was originally because vapour pressure of a liquid depends only on temperature and not volume.