Explain why boiling point of solution is greater than that of pure solvent ?

Explanation

When a non volatile solute is added to a pure solvent at its boiling point, the vapour pressure of the solution is lowered below 1 atm. To bring the vapour pressure again to 1 atm the temperature of the solution has to be increased. As a result, the solution boils at a higher temperature `(T_(b))` than the boiling point of the puire solvent `T_(b) ^(@)).` This increase in the boiling point is known as elevation of boiling point `Delta T_(b) =T_(b)-T_(b)^(@).`