Precipitation Reactions

Precipitation reactions occur when the resulting product of an aqueous solution is insoluble. This means that there is a solid produced, called the precipitate. The precipitate is a combination of cation and anions forming an ionic bond. Precipitates are used in manufacturing chemicals, so that certain ions can be isolated by forming precipitates with them. We can predict if a precipitate is produced using the solubility rules for common ionic solids:

1. Salts of Group 1 cations (with some exceptions for Li⁺) and the NH₄⁺ cation are soluble.
2. Nitrates, acetates, and perchlorates are soluble.
3. Salts of silver, lead, and mercury(I) are insoluble.
4. Chlorides, bromides, and iodides are soluble.
5. Carbonates, phosphates, sulfides, oxides, and hydroxides are insoluble (sulfides of Group 2 cations and hydroxides of Ca²⁺ , Sr²⁺, and Ba²⁺ are slightly soluble).
6. Sulfates are soluble except for those of calcium, strontium, and barium.