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Date	November 2020	Marks available	3	Reference code	20N.2.hl.TZ0.6
Level	HL	Paper	2	Time zone	TZ0
Command term	Explain	Question number	6	Adapted from	N/A

Question

The electron configuration of copper makes it a useful metal.

Determine the frequency of a photon that will cause the first ionization of copper. Use sections 1, 2 and 8 of the data booklet.

[2]

The electron configuration of copper makes it a useful metal.

Explain why a copper(II) solution is blue, using section 17 of the data booklet.

[3]

The electron configuration of copper makes it a useful metal.

Copper plating can be used to improve the conductivity of an object.

State, giving your reason, at which electrode the object being electroplated should be placed.

[1]

Markscheme

$« E = \frac{745 000 J {mol}^{- 1}}{6.02 \times 10^{23} {mol}^{- 1}} = » 1.24 \times 10^{- 18} J$ ✔

$« E = h ν »$
$« 1.24 \times 10^{- 18} J = 6.63 \times 10^{- 34} J s \times ν »$
$ν = 1.87 \times 10^{15} « s^{- 1} / Hz »$ ✔

Award [2] for correct final answer.
Award [1] for 1.12 × 10³⁹ «Hz».

orange light is absorbed «and the complementary colour is observed» ✔

Any TWO from:
partially filled d-orbitals ✔
«ligands/water cause» d-orbitals «to» split ✔
light is absorbed as electrons move to a higher energy orbital «in d–d transitions»
OR
light is absorbed as electrons are promoted ✔
energy gap corresponds to «orange» light in the visible region of the spectrum ✔

cathode/negative «electrode» AND ${Cu}^{2 +}$ reduced «at that electrode» ✔

Accept cathode/negative «electrode» AND copper forms «at that electrode».

Examiners report

Determining the frequency of a photon that will cause the first ionization of copper was the most challenging question on the exam. Many could not do it all, although some came up with the answer that came from using the result that would arise from the ionization energy in J/mole (and frequently kJ/mole) rather than J/atom.

Many students were able to fully explain why solutions containing Cu²⁺ appear blue, however the misconception between absorption and emission spectra is still quite evident.

Surprisingly not that well answered. Most students identified the cathode as the electrode where electroplating occurs but few could adequately justify why.

Syllabus sections

Additional higher level (AHL) » Topic 13: The periodic table—the transition metals » 13.2 Coloured complexes

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Additional higher level (AHL) » Topic 13: The periodic table—the transition metals

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