Colligative property

In physical chemistry of dilute solutions, the colligative property (from Latin colligere "collect") is a substance property (e.g. vapor pressure) that only depends on the number of particles (i.e. the amount of substance ) of the dissolved component, but not on the type of the particles or their chemical composition.

examples are

• Lowering of vapor pressure
• Depression of freezing point ( cryoscopy )
• Boiling point increase ( ebullioscopy )
• Osmotic pressure

The colligative properties are only strictly independent of the type of particle if they do not participate in the phase transition. This applies to vapor pressure depression and boiling point elevation, so for dissolved substances compared to solvent negligible vapor pressure have so z. B. for salts that are dissolved in water, but not for a solution of ethanol in water.

Physically, the colligative properties can be derived from the fact that the dissolved substances reduce the chemical potential of the solvent due to their entropy of mixing .

See also

• Kelvin equation
• Clausius-Clapeyron equation
• Solution effect

Web links

• Video: Phase Equilibria of Ideal Mixtures: Raoult's Law and the Colligative Consequences . Jakob Günter Lauth (SciFox) 2013, made available by the Technical Information Library (TIB), doi : 10.5446 / 15230 .

Individual evidence

1. ↑ Bruno P. Kremer, Horst Bannwarth: Introduction to Laboratory Practice . Springer, Berlin Heidelberg 2014, ISBN 978-3-642-54333-3 , p. 135 , doi : 10.1007 / 978-3-642-54334-0 .
2. ↑ ^{a b c d} Brockhaus ABC Chemie , VEB FA Brockhaus Verlag Leipzig 1965, p. 705.