Elevation in the boiling point refers to a condition where the temperature at which a solvent vaporizes is upraised.
This phenomenon is a result of the introduction of a non-volatile solute is to the pure solvent.
The non-volatile solute on adding to the pure solvent disturbs the molecular interaction between the solvent molecule.
This reduces the capability of the solvent molecule to transform from the liquid phase to the gaseous phase. The vapour pressure of the solvent is brought down.
Thus more energy is required to vaporize the solvent. This energy is provided in the form of an increase in temperature.
Explanation:
Salt is a non-volatile solute. When it is added to pure water, it interacts with the water molecules and also occupies sites between the top layer of water molecules.
The intermolecular attraction between salt-water molecules is greater than water-water molecules.
When water is heated at 100ºC ( Boiling Point of water), the salt molecules makes it difficult for the water molecules to evaporate due to greater attractive forces.
So, to reach the vaporization stage higher temperature is required. Therefore, when salt is added to water, the boiling point of water increases.