Silver Nitrate Test for Halide Ions

The silver nitrate test identifies halide ions (Cl⁻, Br⁻ and I⁻) in solution.Method
1. Put a small volume of the unknown solution in a test tube.
2. Add dilute nitric acid.
3. Add a few drops of silver nitrate solution, AgNO₃(aq).
4. Observe the colour of any precipitate.Silver ions react with halide ions to form an insoluble silver halide precipitate. The general ionic equation is:Ag⁺(aq) + X⁻(aq) → AgX(s)The nitrate ions and the metal ions from the halide salt are spectator ions, so they are left out of the ionic equation.Each silver halide has a different colour, which identifies the halide. Because some colours look similar, the result can be confirmed by adding ammonia solution.Silver fluoride is soluble in water, so fluoride ions give no precipitate. This test cannot be used to identify fluoride.Worked example: write the ionic equation, with state symbols, for silver nitrate reacting with potassium bromide solution.
The full equation is:
AgNO₃(aq) + KBr(aq) → AgBr(s) + KNO₃(aq)
K⁺ and NO₃⁻ are spectator ions, so the ionic equation is:
Ag⁺(aq) + Br⁻(aq) → AgBr(s)The nitric acid is added first to remove other ions, such as carbonate, that would also give a precipitate with silver ions.