Final answer:
A precipitation reaction occurs when two solutions containing a cation and an anion are mixed. This type of reaction is called a double displacement reaction. In this reaction, a solid precipitate is formed.
Step-by-step explanation:
A precipitation reaction occurs when two solutions containing a cation (red spheres) and an anion (green spheres) are mixed. This type of reaction is called a double displacement reaction. In a double displacement reaction, the cations and anions in the solutions switch places, forming two new compounds. In this case, when the solutions are mixed, a solid precipitate is formed, which is the characteristic of a precipitation reaction.