| The solubility of compounds
depends on the similarity of the solute and solvent. The basic rule of
solubility is "like dissolves like." Polar covalent
compounds dissolve in polar solvents and nonpolar compounds dissolve in nonpolar
solvents. Thus ammonia, NH3, which is polar
and hydrogen bonding is soluble in water. Methane, CH4,
which
is
nonpolar, is insoluble in water.
Ionic compounds, which can be
thought of as very
polar, often are
soluble in water, although not always. We use a set of solubility rules
to help
us remember the solubility of ionic compounds.
- Compounds of alkali metal cations always are soluble.
|
- Nitrates, acetates, chlorates, and perchlorates always are soluble.
|
- Chlorides, bromides, and iodides usually are soluble. Exceptions
are Ag+,
Hg2+2, and Pb+2.
|
- Sulfates often are soluble. Exceptions are Ba+2,
Hg+2, and Pb+2.
|
- Sulfides, hydroxides, oxides, chromates, carbonates, and phosphates
seldom are soluble.
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