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8 (a) FA 5, FA 6 and FA 7 are solutions, some of which contain ions that are listed on pages 10 and 11 - CIE - A-Level Chemistry - Question 3 - 2017 - Paper 1
Question 3
8 (a) FA 5, FA 6 and FA 7 are solutions, some of which contain ions that are listed on pages 10 and 11. (i) To a 0.5 cm depth of solution in a boiling tube add aque... show full transcript
Worked Solution & Example Answer:8 (a) FA 5, FA 6 and FA 7 are solutions, some of which contain ions that are listed on pages 10 and 11 - CIE - A-Level Chemistry - Question 3 - 2017 - Paper 1
Step 1
(i) Identify as many ions present in FA 5, FA 6 and FA 7 as possible from your observations.
Answer
Based on the observations:
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FA 5: Cation present is likely (due to the formation of a blue precipitate with sodium hydroxide). Anion present could be ext{OH}^- (formation of precipitate).
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FA 6: Cation is likely (indicated by the decolorization of the purple potassium manganate(VII) solution). Anion is unknown.
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FA 7: Cation is (sodium in sodium nitrate), and anion is (nitrate).
Step 2
(ii) Describe another test you could carry out to confirm the identity of a cation you have identified in (i).
Answer
To confirm the presence of ions in FA 6, you can carry out a test using ammonium thiocyanate (NH₄SCN). When mixed with ions, it will produce a blood-red colored complex if is present. The expected observation would be a color change to blood red upon addition of the reagent.
- Reagent: Ammonium thiocyanate (NH₄SCN).
- Expected Observation: Formation of a blood-red colored solution.
Step 3