These are examples of possible double replacement reactions. They're also called precipitation reactions because if there’s a reaction a solid precipitate is produced. No precipitate will form if the possible products are both soluble in water.

The first set of solutions forms a precipitate because silver chloride is insoluble in water:

`Ag^+_(aq) + Cl^-_(aq)-> AgCl_((s))`

Set b has no reaction. The possible products, copper(II)nitrate and sodium chloride, are both soluble in water.

Set c has no reaction. The possible products, ammonium hydroxide and potassium chloride, are both soluble in water.

You can determine if an ionic compound is soluble by using a solubility table. There are three rules that are easy to memorize because they have no exceptions. Knowing these will help you determine the outcome of many double replacement reactions.

1. Salts containing alkali metal ions are always soluble.

2. Salts containing the nitrate ion are always soluble.

3. Salts containing the ammonium ion are always soluble.

The link below takes you to a more complete set of solubility rules.