1. 1
   A food safety laboratory is comparing two methods for checking the metal ion content of a batch of mineral water: a traditional flame test performed by an analyst, and flame emission spectroscopy performed by an automated instrument.

   (a)

   Which of the following is an advantage of the instrumental method over the traditional flame test?

   [1 mark]

   • AIt is more accurate, sensitive and rapid
   • BIt requires no calibration against reference data
   • CIt can only be used for non-metal ions
   • DIt produces a coloured precipitate instead of a spectrum

   (b)

   The laboratory's instrument produces a chart showing distinct peaks at specific positions for the mineral water sample. What does flame emission spectroscopy actually measure to produce this chart?

   [1 mark]

   • AThe change in pH caused by dissolving the sample in water
   • BThe light emitted by metal ions when they are heated in a flame
   • CThe mass lost when the sample is heated to dryness
   • DThe colour of a precipitate formed with sodium hydroxide

   (c)

   The laboratory manager wants to justify to inspectors why the company switched from manual flame tests to flame emission spectroscopy for routine testing. Give two reasons, other than cost, why instrumental methods are generally preferred over chemical tests for identifying metal ions.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A geologist analyses a dissolved rock sample using flame emission spectroscopy and compares the resulting spectrum against a reference set of spectra for known metal ions in the laboratory's database.

   (a)

   What is the purpose of comparing the sample's spectrum to reference spectra?

   [1 mark]

   • ATo calculate the relative formula mass of the rock sample
   • BTo measure the boiling point of the rock sample
   • CTo determine whether the rock sample is a pure element
   • DTo identify which metal ions are present by matching peak positions

   (b)

   The geologist's spectrum shows a strong peak that matches the reference peak for sodium ions, but no peak matching potassium. Based on this, what can the geologist reasonably conclude?

   [1 mark]

   • AThe rock sample must be a pure sodium compound
   • BBoth sodium and potassium ions are present in equal amounts
   • CSodium ions are present in the rock sample and potassium ions are not detected
   • DThe rock sample contains no metal ions at all

   (c)

   The geologist is asked to explain to a non-specialist colleague, using the rock sample as the example, how flame emission spectroscopy allows a mixture of metal ions to be identified from a single sample, without needing separate flame tests for each ion.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A hospital toxicology unit needs to determine which metal ion is responsible for a patient's suspected heavy metal poisoning, using a blood sample.

   (a)

   Explain why the unit would choose flame emission spectroscopy rather than a manual flame test or sodium hydroxide precipitation test for this investigation, referring to the nature of the sample and the requirements of the analysis.

   [3 marks]

   (b)

   The toxicology unit obtains a spectrum from the patient's blood sample showing a peak at a wavelength that closely matches the reference peak for lead ions, but the peak intensity is much lower than in the reference spectrum for a known concentrated lead sample. Explain what this pattern of results suggests about the patient's blood sample, and describe one limitation of relying on peak intensity alone when interpreting instrumental data.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A national water regulator is deciding whether to require all water companies, including small rural suppliers, to switch from manual chemical tests (flame tests, sodium hydroxide precipitation and precipitation tests for anions) to flame emission spectroscopy for monitoring metal ion contamination in drinking water.

   (a)

   Discuss the advantages and possible disadvantages of making instrumental analysis compulsory for all water companies, including small rural suppliers, and explain how the regulator might balance these factors when making its decision.

   [6 marks]

   (b)

   A small rural water supplier objects to the new regulation, arguing that its existing manual chemical tests (flame tests, sodium hydroxide solution and precipitation tests for anions) have never previously detected a contamination problem and are much cheaper to run. Evaluate this argument, explaining the scientific limitations of manual chemical tests compared with flame emission spectroscopy, and suggest a compromise the regulator could offer that still improves detection reliability without imposing the full cost of instrumental analysis on the supplier immediately.

   [6 marks]

   Total for question 4: 12 marks

End of questions