Flame tests and chemical reagents are used to identify the ions present in unknown compounds.
(i) Suggest two reasons why nichrome is often used as a suitable alternative to platinum for the wire in flame tests.
(ii) Why is the wire dipped in concentrated hydrochloric acid during the cleaning process?
(iii) Why is a yellow, luminous Bunsen flame not suitable for observing a flame test?
Three metal compounds, DDD, EEE, and FFF, are tested separately with various diagnostic reagents. The results of these tests are shown in the table below:
| Metal compound | Flame test | Aqueous acidified silver nitrate | Aqueous acidified barium chloride | Aqueous sodium hydroxide |
|---|---|---|---|---|
| D | crimson | yellow precipitate | no precipitate | no precipitate |
| E | yellow | no precipitate | white precipitate | no precipitate |
| F | no colour | no precipitate | no precipitate | green precipitate |
(i) Give the chemical name of compound D D\,D and of compound EEE.
(ii) Identify the cation present in compound FFF.
Describe a chemical test that could be used to show that a solid sample of a compound contains ammonium ions (NH4+\text{NH}_4^+NH4+).
35 exam-style questions on Edexcel IGCSE Chemistry Chemical tests. Each one has a worked solution and a mark scheme showing where the marks go.