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Chemistry · Glossary

What is Colligative property?

Also known as: cryoscopic constant · ebullioscopic constant

Definition 3.20 University Chemistry — Year 2 · Chapter 3 — Chemical Potential and Mixtures

A colligative property of a dilute solution is one that depends on the amount of dissolved particles per amount of solvent and not on their nature: the lowering of the vapour pressure, of the freezing point, the raising of the boiling point, and the osmotic pressure. The constants of the freezing-point and boiling-point laws below are the cryoscopic constant KfK_f and the ebullioscopic constant KbK_b of the solvent.

Chemical potential of the solvent against temperature (schematic, at fixed pressure). The stable phase is the one of lowest . Dissolving a solute lowers the liquid’s line by RT x_1 < 0; it now meets the solid’s line at a lower temperature: the solution freezes below the pure solvent.
Chemical potential of the solvent against temperature (schematic, at fixed pressure). The stable phase is the one of lowest μ\mu. Dissolving a solute lowers the liquid’s line by RTln⁡x1<0RT\ln x_1 < 0; it now meets the solid’s line at a lower temperature: the solution freezes below the pure solvent.
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