1. 1
   A jeweller finds an unlabelled sample of metal salt and wants to identify which metal ion it contains before using it to make coloured glass. A colleague suggests using a flame test.

   (a)

   Which general method does a flame test rely on to identify a metal ion?

   [1 mark]

   • AMeasuring the melting point of the salt
   • BObserving the characteristic colour produced when the salt is heated in a flame
   • CDissolving the salt and measuring its pH
   • DWeighing the salt before and after heating

   (b)

   Before carrying out the flame test, the jeweller cleans a piece of nichrome wire by dipping it in acid and holding it in a hot flame until no colour is produced. Why is this cleaning step necessary?

   [1 mark]

   • ATo sharpen the wire so it holds more sample
   • BTo make the wire magnetic
   • CTo cool the wire down before use
   • DTo remove any residue from previous tests that could give a false or contaminated colour

   (c)

   Explain, in general terms, why different metal ions produce different flame colours when heated, and state why flame tests are useful for identifying metal ions.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student is given an unknown white solid and told it contains one of several possible metal ions, including calcium, magnesium and aluminium. The student is advised that a flame test may not distinguish between all of these ions.

   (a)

   Which of these metal ions does NOT produce a distinctive flame colour, meaning a different test is needed?

   [1 mark]

   • ACalcium
   • BSodium
   • CAluminium and magnesium
   • DPotassium

   (b)

   Given this limitation, what should the student do to reliably identify which specific metal ion is present in the unknown solid?

   [1 mark]

   • AUse an additional confirmatory test, such as adding sodium hydroxide solution and observing any precipitate formed
   • BRely solely on the flame test result, even if inconclusive
   • CAssume the ion is calcium because it is the most common
   • DRepeat the flame test using a different flame colour each time

   (c)

   Explain why relying on a single identification method can sometimes lead to an incorrect or incomplete conclusion when identifying metal ions, using the example of calcium, magnesium and aluminium given above.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A pharmaceutical company receives a batch of a metal salt used in a supplement and needs to confirm the identity of the metal ion before approving it for use, as an incorrect metal ion could pose a health risk.

   (a)

   Describe an overall strategy, combining more than one type of test, that the company's laboratory could use to reliably identify the metal ion present.

   [3 marks]

   (b)

   The laboratory's flame test produces a faint lilac colour, but a technician is unsure whether this indicates potassium or is simply a weak/contaminated result. Explain what steps the laboratory should take to resolve this uncertainty and reach a confident conclusion.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A recycling centre receives a mixed batch of unlabelled metal salt residues from an industrial process and needs to sort them by identifying which metal ion each sample contains, so that they can be processed and recycled correctly.

   (a)

   Describe, in detail, a complete strategy the centre could use to identify metal ions across a wide range of possible samples, explaining why more than one type of test is needed overall.

   [6 marks]

   (b)

   One sample in the batch gives a flame colour that appears to be a mixture of yellow and lilac, making it difficult for the recycling centre to be sure which metal ions are present. Evaluate why this ambiguous result occurs, and discuss the steps the centre should take to resolve it and correctly identify the metal ions in this sample.

   [6 marks]

   Total for question 4: 12 marks

End of questions