question_answer 1)

A liquid is in equilibrium with its vapours 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 the vapour pressure? (b) How do the rates of evaporation and condensation change initially? (c) What happens when the equilibrium is restored finally and what will be the final vapour pressure?

Answer:

(a) Initially, the vapour pressure decreases because the same amount of vapours now occupies more space. (b) The rate of evaporation increases while the rate of condensation decreases initially. (c) At equilibrium, the rate of evaporation and condensation becomes same and final vapour pressure will be same as that before increasing the volume.