Question

what is elevation of boiling point?

Answer 1

Boiling-point elevation describes the phenomenon that the boiling point of a liquid will be higher when another compound is added, meaning that a solution has a higher boiling point than a pure solvent. This happens whenever a non-volatile solute, such as a salt, is added to a pure solvent, such as water

Answer 2

Hey !!

Boiling point is the temperature at which the vapour pressure of a liquid becomes equal to the atmospheric pressure. When a non-volatile solute is added to a volatile solvent, the vapour pressure of the solvent decreases. In order to make this solution boil at vapour pressure must be increased by raising the temperature above the boiling point of the pure solvent. The difference in the boiling point of solution (T°b) and that of pure solvent (Tb) is called elevation of boiling point (ΔTb).

Elevation of boiling point = ΔTb = Tb - T°b

For dilute solution, it has been observed that the elevation of boiling point is directly proportional to the molal concentration of the solute in the solution.

           ΔTb α m (or) ΔT = Kbm

where Kb is a constant called molal elevation constant or ebullioscopic constant.

When m = 1 mol kg⁻¹, ΔTb = Kb

Hence, molal elevation constant many be defined as the elevation in boiling point when one mole of a non-volatile solute is dissolved in one kilogram ( 1000 g ) of solvent. The unit of Kb is K kg mol⁻¹

As,              m = Wb × 1000 / Mb × Wa

Therefore, ΔTb = Kb × Wb × 1000 / Mb × Wa

                 Mb = Kb × Wb × 1000 / ΔTb × Wa

Hope it helps you !!