(1) Solutions of sodium chloride and silver nitrate react with each other forming a precipitate of silver chloride and a solution of sodium nitrate.
White precipitate of AgCl is formed by exchange of ions Ag+ and Cl- between the reactants.
(2) Barium suiphide reacts with zinc sulphate to form zinc sulphide and a white precipitate of barium sulphate.
white precipitate is formed by exchange of ions Ba++ and SO4— between the reactants.