Answer:

When two soluble salt solutions are mixed, the ions are exchanged between the compounds in a twofold displacement reaction. When one of these chemicals is solid (insoluble in water), it sinks to the bottom of the container. The precipitate solid is named after the precipitation reaction. Precipitation responses include:

CdSO₄(aq) + K₂S(aq) → CdS(s) + K₂SO₄(aq)

2NaOH(aq) + MgCl₂(aq) → 2NaCl(aq) + Mg(OH)₂(s)