Ebullioscopic constant

In thermodynamics, the ebullioscopic constant relates molality to boiling point elevation.[1] It is the ratio of the latter to the former:

  • is the van 't Hoff factor, the number of particles the solute splits into or forms when dissolved.
  • is the molality of the solution.

A formula to compute the ebullioscopic constant is:[2]

Through the procedure called ebullioscopy, a known constant can be used to calculate an unknown molar mass. The term "ebullioscopy" comes from the Latin language and means "boiling measurement." This is related to cryoscopy, which determines the same value from the cryoscopic constant (of freezing point depression).

This property of elevation of boiling point is a colligative property. It means that the property, in this case , depends on the number of particles dissolved into the solvent and not the nature of those particles.

Some values[3]

Solvent (in K*kg/mol)
Acetic acid3.08
Carbon disulfide2.34
Carbon tetrachloride5.03
Diethyl ether2.02

See also


  1. "Ebullioscopic Constant". CHEMISTRY GLOSSARY.
  2. Martin, Chaplin. "Colligative Properties". London South Bank University. London South Bank University.
  3. P. W. Atkins, Physical Chemistry, 4th Ed., p. C17 (Table 7.2)

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