DP Chemistry (last assessment 2024)

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Question 22M.2.hl.TZ2.8a(ii)

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Date May 2022 Marks available [Maximum mark: 2] Reference code 22M.2.hl.TZ2.8a(ii)
Level hl Paper 2 Time zone TZ2
Command term Explain Question number a(ii) Adapted from N/A
a(ii).
[Maximum mark: 2]
22M.2.hl.TZ2.8a(ii)

Carbon forms many compounds.

C60 and diamond are allotropes of carbon.

(a(ii))

Explain why C60 and diamond sublime at different temperatures and pressures.

[2]

Markscheme

diamond giant/network covalent AND sublimes at higher temperature ✔

C60 molecular/London/dispersion/intermolecular «forces» ✔

 

Accept “diamond has strong covalent bonds AND require more energy to break «than intermolecular forces»” for M1.

Examiners report

Again, this was a struggle between intermolecular forces and covalent bonds and this proved to be even harder than (a)(i) with only 25% of candidates getting full marks. The distinction between giant covalent/covalent network in diamond and molecular in C60 and hence resultant sublimation points, was rarely explained. There were many general and vague answers given, as well as commonly (incorrectly) stating that intermolecular forces are present in diamond. As another example of insufficient attention to the question itself, many candidates failed to say which would sublime at a higher temperature and so missed even one mark.

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