What is vapour pressure of liquids? How the vapour pressure of a liquid is related to its boiling point?

Explanation

IF a liquid is taken in an evacuated container a portion of liquid evaporates. This is due to collisions between the liquid molecules, The molecules which gets more energy due to molecular collisions within the liquid escape from the surface of liquid and goes into vapour. The pressure exerted by the vapours on the walls of container is called vapour pressure.
THe vapour molecules also strike the surface of the liquid. If the kinetic energy of vapour molecules is less than the attractive forces of the liquid molecule on the surface of liquid of vapour molecules goes into the liquid. It is known as condensation.
In the beginning the rate of evaporation is more but the rate of condensation zero. As time posses the rate of evaporation decrease while the rate of condensation increases due to increase in vapour. After sometime the rate of evaporation and rate of condensation become equal and an equilibrium is attained. At this stage the vapour pressure is constant and it is called saturated vapour pressure or equilibrium pressure.
When temperature of a liquid is increased the rate of vapourisation increases. The temperature at which the vapour pressure of a liquid becomes equal to the external pressure the liquid boils . The temperature which the liquid boils is called boiling point.
At I atm pressure the boiling temperature is called normal boiling point. If pressure is 1 bar then the boiling point is called standard boiling point.