Precipitation reactions happen when two soluble salts mix in a liquid solution. This causes an insoluble solid to form, which we call a precipitate.

Here’s a simple way to think about it:

When we mix two salts together in water:

$$AB_{(aq)} + CD_{(aq)} \rightarrow AD_{(s)} + CB_{(aq)}$$

This means that the salts (AB and CD) combine to create a solid (AD) and a new salt (CB) that stays dissolved in the water.

Things That Affect Solubility:

1. Temperature: Usually, when the temperature goes up, more solids can dissolve in the liquid.

2. Pressure: This mostly affects gases. Higher pressure helps more gas dissolve in liquids.

3. Type of Solvent: Solvents that are polar, like water, do a better job of dissolving ionic compounds than non-polar solvents.

4. Common Ion Effect: If there’s already an ion in the solution, it makes it harder for other similar ions to dissolve.

Most inorganic salts (over 90%) can dissolve in water. But there are some exceptions, like silver chloride ($AgCl$) and barium sulfate ($BaSO_4$), which do not dissolve well at all.