colligative properties


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Related to colligative properties: Freezing point depression

colligative properties,

properties of a solutionsolution,
in chemistry, homogeneous mixture of two or more substances. The dissolving medium is called the solvent, and the dissolved material is called the solute. A solution is distinct from a colloid or a suspension.
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 that depend on the number of solute particles present but not on the chemical properties of the solute. Colligative properties of a solution include freezing point (see freezingfreezing,
change of a substance from the liquid to the solid state. The temperature at which freezing occurs for a pure crystalline solid is called the freezing point and is a characteristic of the particular substance.
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), boiling pointboiling point,
temperature at which a substance changes its state from liquid to gas. A stricter definition of boiling point is the temperature at which the liquid and vapor (gas) phases of a substance can exist in equilibrium.
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, osmotic pressure (see osmosisosmosis
, transfer of a liquid solvent through a semipermeable membrane that does not allow dissolved solids (solutes) to pass. Osmosis refers only to transfer of solvent; transfer of solute is called dialysis.
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), and solvent vapor pressurevapor pressure,
pressure exerted by a vapor that is in equilibrium with its liquid. A liquid standing in a sealed beaker is actually a dynamic system: some molecules of the liquid are evaporating to form vapor and some molecules of vapor are condensing to form liquid.
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. By measuring these properties and comparing them with the corresponding properties of the pure solvent, it is possible to determine the number of particles of solute present in the solution. If the mass of solute present is also known, the number-average molecular weightmolecular weight,
weight of a molecule of a substance expressed in atomic mass units (amu). The molecular weight may be calculated from the molecular formula of the substance; it is the sum of the atomic weights of the atoms making up the molecule.
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 can be calculated by dividing the mass of solute by the number of particles present to obtain the average mass per particle.

colligative properties

[kə′lig·ə·div ‚präp·ərd·ēz]
(physical chemistry)
Properties dependent on the number of molecules but not their nature.