Identification of ions by chemical and spectroscopic means (chemistry only)

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Question 27
Medium

This question is about qualitative chemical analysis.

An analyst investigated calcium bromide solution and potassium sulfate solution using flame tests and precipitation reactions.

This is the method used for the flame tests:

  1. Dip a clean nichrome wire in calcium bromide solution.
  2. Put the wire in a roaring blue Bunsen burner flame.
  3. Record the flame colour produced.
  4. Repeat steps 1 to 3 using the same wire but using potassium sulfate solution.
a.

What flame colour is produced by calcium bromide solution?

[1]
b.

Potassium compounds produce a lilac flame colour. The analyst did not clean the wire before reusing it for the potassium sulfate test. As a result, the analyst’s second flame test did not produce a distinct lilac flame colour. Explain why.

[2]
c.

The analyst added sodium hydroxide solution to:

  • calcium bromide solution
  • potassium sulfate solution.

Give the observation for each of these tests.

[2]
d.

To test for bromide ions, the analyst added dilute nitric acid to calcium bromide solution. Name the solution that would show the presence of bromide ions when added to this mixture.

[1]
e.

To test for sulfate ions, the analyst added dilute hydrochloric acid to potassium sulfate solution. Name the solution that would show the presence of sulfate ions when added to this mixture, and give the observation that confirms their presence.

[2]

Identification of ions by chemical and spectroscopic means (chemistry only) Questions

  1. GCSE
  2. /Chemistry
  3. /Identification of ions by chemical and spectroscopic means (chemistry only)