Boiling Point Elevation in Solutions

The boiling point of pure water is 100°C, but that boiling point can be elevated by the adding of a solute such as a salt. A solution typically has a measurably higher boiling point than the pure solvent.

A treatment of boiling point elevation is given by Ebbing. The boiling point elevation ΔTb is a colligative property of the solution, and for dilute solutions is found to be proportional to the molal concentration cm of the solution:

ΔTb = Kbcm

Where Kb is called the boiling-point-elevation constant.

Solutions may be produced for the purpose of raising the boiling point and lowering the freezing point, as in the use of ethylene glycol in automobile cooling systems. The ethylene glycol (antifreeze) protects against freezing by lowering the freezing point and permits a higher operating temperature by raising the boiling point.

Freezing point depression by dissolved material
Table of boiling-point-elevation constants

Chemistry concepts

Sec. 12.6
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