Double Displacement Reactions

Reactions in which there is an exchange of ions between the reactants, are called double displacement reactions.

For example,

Na₂SO₄ (aq) + BaCl₂ (aq) → BaSO₄ (s)↓ + 2NaCl

The white precipitate of BaSO₄ is formed by the reaction of Ba²⁺ ions and SO₄^2– ions. The other product formed is sodium chloride which remains in solution.