When two aqueous solutions are mixed and a white insoluble solid forms, what type of reaction is this?

Correct answer: Precipitation reaction

An insoluble solid formed when two aqueous solutions are mixed is called a precipitate. Therefore, this is a precipitation reaction. For example, mixing silver nitrate and sodium chloride solutions produces a white precipitate of silver chloride. In a neutralisation reaction, an acid and a base generally form salt and water; formation of an insoluble solid is not its defining feature.