Identification of Anions (CIE IGCSE Chemistry)

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Identification of Anions

12-3-1-anions-tests

  • The acidification with aqueous silver nitrate and aqueous barium nitrate / chloride is done to remove ions that might give a false positive result
    • The most common ion that is removed is the carbonate ion
    • The choice of acid has to be considered so that it does not influence the results
    • For example, aqueous silver nitrate solution should not be acidified with hydrochloric acid as this will form a white precipitate due to the chloride ion in the acid
    • For example, aqueous barium nitrate / chloride solution should not be acidified with sulfuric acid as this will form a white precipitate due to the sulfate ion in the acid

Exam Tip

When it comes to qualitative inorganic analysis, always remember that there will be a test for the metal cation part of the molecule and another test for the anion part. 

If you are an extended level student you may be asked to write balanced ionic equations for cation and anions tests, so make sure you know the formulae of all the ions and precipitates formed.

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Stewart

Author: Stewart

Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Topic Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.