- The vapour pressur in the cointainer y is higher than the vapour pressure in the container x . - When the value is opened, the vapour from container y diffuse in the container x and condense there. - When the equilibrium is re-established, the mass of liquid water in the contaier y decreases and container x increases. Hence the answer is, option ( A ) i.e. The final pressure in each container is 31 mm .