Boiling point elevation (ebullioscopy)


Colligative properties are properties of solutions that depend upon the ratio of the number of solute particles to the number of solvent molecules in a solution, and not on the type of chemical species present. This number ratio can be related to the various units for concentration of solutions. Colligative properties result because of the dissolution of nonvolatile solute in a volatile liquid solvent. They are independent of the nature of the solute particles, and are due essentially to the dilution of the solvent by the solute. The boiling point elevation is a colligative property. Boiling-point elevation describes the phenomenon that the boiling point of a liquid (a solvent) will be higher when another compound is added, meaning that a solution has a higher boiling point than a pure solvent. An ebullioscope is an instrument for measuring the boiling point of a liquid. The boiling point of a liquid is the temperature at which its vapor pressure is equal to the external pressure. The normal boiling point is the boiling point at a pressure equal to 1 atmosphere. The boiling point of a pure solvent is increased by the addition of a non-volatile solute, and the elevation can be measured by ebullioscopy.

Related formulas


ΔTbBoiling point elevation (K)
ivan 't Hoff factor (dimensionless)
KbEbullioscopic constant (0.512°C kg/mol for water) (K*kg/mol)
mmolality (mol/kg)