CHEM869A-Info037

Precipitation reactions
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Many precipitation reactions may be predicted by memorizing a set of solubility rules. While these rules help if no other information is available, the result is qualitative and there are exceptions. Some of the common exceptions are part of the rules. Precipitation reactions are usually written as net ionic reactions to emphasize the reacting ions. These same net ionic reactions are the basis for equilibrium calculations which predict solubility quantitatively.

Solubility Rules for Common Ions in Water

Mostly Soluble:

Salts of alkali metals (Group 1A) are soluble.
Ammonium salts are soluble.
All nitrates, acetates, chlorates, and perchlorates are soluble.

Mostly Soluble with more exceptions:

Chlorides are soluble except compounds of Ag, Pb, and Hg(I).
Bromides and iodides are soluble except compounds of Ag, Pb, Hg(I), and Hg(II).
Sulfates are soluble except compounds of Ag, Pb, Hg, Ba, Sr, and Ca.

Mostly Insoluble except for Alkali Metals and Ammonium:

Hydroxides are insoluble except compounds of Ba, Sr, and Ca which are slightly soluble.
Sulfides are insoluble except compounds of Ba, Sr, and Ca which are slightly soluble.
Sulfites are insoluble.
Carbonates and phosphates are insoluble.

Quiz 1C

Quiz 2S

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