Entropy of evaporation

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The entropy of evaporation describes the change in the entropy of a liquid during transition into the gas phase .

Pictet-Trouton's rule

The standard entropy of evaporation of liquids follows the Pictet-Trouton rule (after Raoul Pictet and Frederick Thomas Trouton ). Accordingly, the value of the standard entropy of evaporation for many non-polar liquids is in the vicinity of ≈ 88–90 J K −1 mol −1 . The reason here is the comparably large increase in “disorder” in the transition from liquid to gas. Strong deviations are mostly due to anomalously strongly interconnected molecules , so liquid water is stabilized by hydrogen bonds and structured more strongly (higher short-range order ), which results in a high standard entropy of evaporation .

See also


  1. Compare Erich Meister: Basic Practical Course in Physical Chemistry: Theory and Experiments , 2nd Edition. Edition 2012, p. 35.