a) Test For Halides e.g Cl^- and I^-

This test involves a precipitation reaction. The silver ions in silver nitrate solution reacts with halide ions to insoluble silver salts.

Ag⁺ (aq) + Cl^- (aq) -----> AgCl (s)

Ag⁺ (aq) + I^- (aq) -----> AgI (s)

The solubility of the silver salt precipitate in dilute nitric or in aqueous ammonia can further help to confirm the identity of the anion.

The dilute nitric acid may be added before or after the addition of silver nitrate solution. It is important to note that dilute hydrochloric acid cannot be used as it introduces chloride ions that interfere with the test.

b) Test for carbonate ion in solution, CO₃^2-

Apart from halide ions, carbonate ions in solution also form a white precipitate with silver nitrate. However, this white precipitate will dissolve when dilute nitric acid is added giving vigorous effervescence with the liberation of carbon dioxide gas.

Ag⁺ (aq) + CO₃^2- (aq) -----> Ag₂CO₃ (s)

Ag₂CO₃ (s) + 2HNO₃ (aq) -----> AgNO₃ (aq) + CO₂ (g) + H₂O (l)