Testing for Anions

Edited by Jamie (ScienceAid Editor), Taylor (ScienceAid Editor)



Ion CO32-, carbonate is found in limestone, or calcium carbonate (CaCO3).

To test for it, you must first: Add a dilute acid to the sample. A gas is given off which when tested should prove to be carbon dioxide.

Sulphate and Sulphide

Sulphate is SO42- and Sulphide is SO32-


By adding barium chloride to the solution you are testing, a white precipitate will form. If you add hydrochloric acid, the sulphate (SO42-) WILL NOT dissolve and the sulphite (SO32-) will.

Halogen Tests

The test for halogens, or halide ions, is to add silver nitrate to a solution. Often, nitric acid is added first as well. If there are chloride, bromide or iodide ions in the solution they will react with silver to form a precipitate. The different precipitates are summarized in the table below.

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results of halogen test, showing corresponding colours

The ionic equations for these reactions are:

  1. 1
    Ag+ (aq) + Cl- (aq) ==>> AgCl (s)
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  2. 2
    Ag+ (aq) + Br- (aq) ==>> AgBr (aq)
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  3. 3
    Ag+ (aq) + I- (aq) ==>> AgI (aq)
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