(a) As volume is increased, the vapour pressure will decrease because the same amount of vapour are now distributed in larger space. Number of molecules striking the wall of container decreases and thus pressure decreases.
(b) As the vessel is sealed, the rate of evaporation remains constant at constant temperature. However, the rate of condensation will be low initially because there are fewer molecules per unit volume in the vapour phase and hence the number of collisions per unit time with the liquid surface decreases.
(c) When equilibrium is restored, Rate of evaporation = rate of condensation. The final vapour pressure =Initial pressure because vapour pressure of a liquid depends only on temperature and not volume.
