Question

Equilibrium vapour pressure or saturated vapour pressure: Vapour pressure in the state of equilibrium between liquid phase and vapour phase.

What does it mean ?

Answer 1

Equilibrium Vapour pressure- If we keep a liquid in closed flask then both evaporation and condensation processes take place in the flask. The molecules in liquid state posses kinetic energy and during collision some molecules gain kinetic energy and move to vapour phase. This process continues till the stage of equilibrium is reached i.e. rate of evaporation is equal to rate of condensation. At this stage, what ever pressure is exerted by vapours above the liquid is termed as equilibrium vapour pressure.