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Date	May 2019	Marks available	2	Reference code	19M.3.hl.TZ2.4
Level	HL	Paper	3	Time zone	TZ2
Command term	Suggest	Question number	4	Adapted from	N/A

Question

Metals are extracted from their ores by several methods, including electrolysis and reduction with carbon.

Determine the mass of aluminium, in g, that could be extracted from an appropriate solution by a charge of 48 250 C. Use sections 2 and 6 of the data booklet.

[3]

Once extracted, the purity of the metal can be assessed using ICP-MS. Suggest two advantages of using plasma technology rather than regular mass spectrometry.

[2]

Explain the action of metals as heterogeneous catalysts.

[2]

Outline how alloys conduct electricity and why they are often harder than pure metals.

Conduct electricity:

Harder than pure metals:

[2]

Carbon nanotubes are added to metals to increase tensile strength.

Write an equation for the formation of carbon nanotubes from carbon monoxide.

[1]

Markscheme

moles of electrons «= $\frac{{48250{\text{ C}}}}{{96500{\text{ C mo}}{{\text{l}}^{ - 1}}}}$ » = 0.5000 «mol» [✔]

moles of aluminium «= $\frac{{0.5000{\text{ mol}}}}{3}$ » = 0.1667 «mol» [✔]

mass of aluminium «= 26.98 g mol^–1 × 0.1667 mol» = 4.50 «g» [✔]

Note: Award [3] for correct final answer.

Any two of:
larger linear calibration [✔]

«accurate» detection of multiple elements/metals [✔]

«accurate» detection of elements in low concentration [✔]

temperature around 10 000 K atomises/ionises every material [✔]

Any two of:
reactant(s) adsorb onto active sites/surface [✔]

bonds weakened/broken/stretched «in adsorbed reactants»
OR
activation energy lowered [✔]

products desorbed [✔]

Note: Accept “products released” for M3.

Conduct electricity:
«delocalized/valence» electrons free to move «under potential difference» [✔]

Harder than pure metals:
atoms/ions of different sizes prevent layers «of atoms/ions» from sliding over one another [✔]

2CO (g) → C (s) + CO₂ (g) [✔]

Examiners report

Many candidates did reasonably well in this question but some struggled with the number of electrons required.

Most candidates did not seem to understand any advantages of using plasma technology rather than regular mass spectrometry.

This question was reasonably answered with many candidates receiving a mark for the action of a catalyst. The terms adsorbed and desorbed were often missing.

Most candidates were awarded one mark for how alloys conduct electricity. Some struggled with describing why they are harder than pure metals.

Carbon nanotubes proved to be difficult for the majority of the candidates. Hardly any candidates stated an equation for the formation of carbon nanotubes from carbon monoxide.

Syllabus sections

Options » A: Materials » A.2 Metals and inductively coupled plasma (ICP) spectroscopy

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