DP Chemistry (last assessment 2024)

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Question 19M.2.hl.TZ2.4e(iii)

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Date May 2019 Marks available [Maximum mark: 1] Reference code 19M.2.hl.TZ2.4e(iii)
Level hl Paper 2 Time zone TZ2
Command term Predict Question number e(iii) Adapted from N/A
e(iii).
[Maximum mark: 1]
19M.2.hl.TZ2.4e(iii)

Rhenium, Re, was the last element with a stable isotope to be isolated.

Rhenium forms salts containing the perrhenate(VII) ion, ReO4−.

(e(iii))

Predict, giving a reason, whether the reduction of ReO4− to [Re(OH)2]2+ would oxidize Fe2+ to Fe3+ in aqueous solution. Use section 24 of the data booklet.

[1]

Markscheme

no AND ReO4− is a weaker oxidizing agent than Fe3+
OR
no AND Fe3+ is a stronger oxidizing agent than ReO4−
OR
no AND Fe2+ is a weaker reducing agent than [Re(OH)2]2+
OR
no AND [Re(OH)2]2+ is a stronger reducing agent than Fe2+
OR
no AND cell emf would be negative/–0.41 V     [✔]

Examiners report

Many students understood that the oxidation of Fe2+ was not viable but were unable to explain why in terms of oxidizing and reducing power; many students simply gave numerical values for EΘ often failing to realise that the oxidation of Fe2+ would have the inverse sign to the reduction reaction.

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