Q12.16P - Chemistry: Molecular Nature Of Matter And Change

Question

A liquid is in equilibrium with its vapour in a closed vessel at a fixed temperature. The vessel is connected by a stopcock to an evacuated vessel. When the stopcock is opened, will the final pressure of the vapour be different from the initial value if

(a) Some liquid remains

(b) All the liquid is first removed?

Step-by-Step Solution

Answer

The final pressure of the vapour will be higher than the initial pressure.

Step1: Vapor Pressure

The vapour pressure is the pressure exerted by the vapours in a thermodynamic equilibrium with its liquid and solid phase in a closed system at a constant temperature.

Step2: When some liquid remains

As some liquid remains in the vessel, the process of vaporization initiates and a thermodynamic equilibrium is again thus reached. Thus, the vapour pressure increases in this condition.

Step 3: Vapor Pressure

The pressure exerted by the vapours under thermodynamic equilibrium with the liquid phase in a closed system at a constant temperature is the vapour pressure.

Step 4: When there is no liquid

As there is no liquid there is no shifting of the thermodynamic equilibrium and thus there is no change in vapour pressure.