It is the temperature at which the Vapour pressure of a solution or solvent becomes equal to atmospheric pressure. Means the temperature at the solvent or solute is ready to boil. Let take an example of water, it boils at 100 degree celcius. So the boiling point of water is 100 degree celcius.
Elevation in Boiling point
When solvent is reacted with non volatile solute the vapour pressure of that solution is lowered and because of it the boiling point of solution is increases. So, we can say that vapour pressure is inversely proportional to boiling point of solution.
From elevation in Boiling point,
∆Tb = kb m (here m means the molality of solution)
And kb is the molal elevation constant or we can call it as ebullioscopic constant. It depends on solvent and unit of kb is Kelvin kg / mol .
So indirectly the ∆Tb depends on number of solute particles therefore it is a colligative property.
It is the property which depends on the number of solute particles not on the nature of solute particles. Like we have seen ∆Tb.