AQA Chemistry 8462 · Paper 2 · 4.8.3.1, 4.8.3.2, 4.8.3.3, 4.8.3.4, 4.8.3.5, 4.8.3.6, 4.8.3.7
Identifying ions
3 marksFoundationChemistry required practical 74.8.3.1 Flame tests
A student carries out flame tests on some metal compounds using a clean nichrome wire loop.
.1One compound gives a lilac flame. Which metal ion does it contain?
[1 mark] .2Give the flame colour of a lithium compound.
[1 mark] .3A second sample contains both sodium ions and potassium ions. Explain why its flame test may not identify both ions.
[1 mark] 4 marksFoundation and HigherChemistry required practical 74.8.3.2 Metal hydroxides
Sodium hydroxide solution is added to solutions of metal ions. Some form coloured precipitates.
.1A solution gives a blue precipitate. Which ion is present?
[1 mark] .2Write the formula of the blue precipitate.
[1 mark] .3Iron(III) ions form a brown precipitate of iron(III) hydroxide. Write a balanced ionic equation for this reaction.
[2 marks] 3 marksFoundation and HigherChemistry required practical 74.8.3.2 Metal hydroxides
Solutions of aluminium ions, calcium ions and magnesium ions all form a white precipitate when a few drops of sodium hydroxide solution are added.
.1Describe how a student could use sodium hydroxide solution to tell aluminium ions apart from magnesium ions.
[2 marks] .2Another solution gives a brown precipitate with sodium hydroxide. Which ion is present?
[1 mark] 4 marksFoundationChemistry required practical 74.8.3.4 Halides
A student tests a solution for halide ions. She adds dilute nitric acid and then silver nitrate solution. A cream precipitate forms.
.1Which ion is in the solution?
[1 mark] .2Explain why dilute nitric acid is added before the silver nitrate.
[2 marks] .3Explain why hydrochloric acid must not be used instead of nitric acid in this test.
[1 mark] 3 marksFoundation and HigherChemistry required practical 74.8.3.3 Carbonates4.8.3.5 Sulfates
A student has a sample of an unknown white solid. It is a single ionic compound.
.1When dilute hydrochloric acid is added the solid fizzes, and the gas turns limewater milky. Which ion does the solid contain?
[1 mark] .2Describe how the student could test a solution of a different compound for sulfate ions. Give the result if sulfate ions are present.
[2 marks] 