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Boiling Point Elevation

What Boiling Point Elevation Is and How It Works

By Anne Marie Helmenstine, Ph.D., About.com

Adding salt to water increases its boiling point.

Adding salt to water increases its boiling point.

Markus Schweiss
Boiling point elevation occurs when the boiling point of a solution becomes higher than the boiling point of a pure solvent. The temperature at which the solvent boils is increased by adding any non-volatile solute. A common example of boiling point elevation can be observed by adding salt to water. The boiling point of the water is increased.

Boiling point elevation, like freezing point depression, is a colligative property of matter. This means it depends on the number of particles present in a solution and not on the type of particles or their mass.

The amount of boiling point elevation can be calculated using the Clausius-Clapeyron equation and Raoult's law. For an ideal dilute solution:

Boiling Pointtotal = Boiling Pointsolvent + ΔTb

where ΔTb = molality * Kb * i

with Kb = ebullioscopic constant (0.52°C kg/mol for water) and i = Van't Hoff factor

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