What do you mean by a precipitation reaction? Explain by giving examples.

Certain chemical reactions are characterized by the formation of insoluble solid substances called precipitates.
Reactions in which precipitate is formed are called precipitation reactions.

$$ Na_{2}SO_{4} (aq) + BaCl_{2} (aq)$$

$$ \downarrow$$

$$ 2Nacl (aq) + BaSO_{4}(s) $$

In the above reaction, when sodium sulphate reacts with barium chloride, the white precipitate of barium sulphate is formed along with the sodium chloride.