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Solutions and Colligative
Properties
IN THIS CHAPTERSummary:Asolutionis a homogeneous mixture composed of a solvent and
one or more solutes. Thesolventis the substance that acts as the dissolving
medium and is normally present in the greatest amount. Commonly the sol-
vent is a liquid, but it doesn’t have to be. Our atmosphere is a solution with
nitrogen as the solvent; it is the gas present in the largest amount (79%).
Many times you will be dealing with a solution in which water is the solvent,
anaqueous solution. Thesoluteis the substance that the solvent dissolves
and is normally present in the smaller amount. You may have more than one
solute in a solution. For example, if you dissolved table salt (sodium chloride)
and table sugar (sucrose) in water, you would have one solvent (water) and
two solutes (sodium chloride and sucrose).
Some substances will dissolve in a particular solvent and others will not.
There is a general rule in chemistry that states that “like dissolves like.”This
general statement may serve as an answer in the multiple-choice questions,
but does not serve as an explanation in the free-response questions. This
simply means that polar substances (salts, alcohols, etc.) will dissolve in polar
solvents such as water, and nonpolar solutes, such as iodine, will dissolve in
nonpolar solvents such as carbon tetrachloride. The solubility of a particular
solute is normally expressed in terms of grams solute per 100 mL of solvent
(g/mL) at a specified temperature. The temperature must be specified
because the solubility of a particular substance will vary with the temperature.
Normally, the solubility of solids dissolving in liquids increases with increasing
temperature, while the reverse is true for gases dissolving in liquids.
A solution in which one has dissolved the maximum amount of solute per
given amount of solvent at a given temperature is called a saturated solution.
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