DP Chemistry (last assessment 2024)

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Question 21M.2.hl.TZ1.3

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Date May 2021 Marks available [Maximum mark: 12] Reference code 21M.2.hl.TZ1.3
Level hl Paper 2 Time zone TZ1
Command term Deduce, Determine, Discuss, Label, Outline, State Question number 3 Adapted from N/A
3.
[Maximum mark: 12]
21M.2.hl.TZ1.3

Magnetite, Fe3O4, is another ore of iron that contains both Fe2+ and Fe3+.

(a)

Deduce the ratio of Fe2+:Fe3+ in Fe3O4.

[1]

Markscheme

1:2 ✔

Accept 2 Fe3+: 1 Fe2+
Do not accept 2:1 only

Iron exists as several isotopes.

(b(i))

State the type of spectroscopy that could be used to determine their relative abundances.

[1]

Markscheme

mass «spectroscopy»/MS ✔

(b(ii))

State the number of protons, neutrons and electrons in each species.

[2]

Markscheme


Award [1 max] for 4 correct values.

(c)

Iron has a relatively small specific heat capacity; the temperature of a 50 g sample rises by 44.4°C when it absorbs 1 kJ of heat energy.

Determine the specific heat capacity of iron, in J g−1 K−1. Use section 1 of the data booklet.

[1]

Markscheme

specific heat capacity « = qm×∆T/1000 J50 g×44 K» = 0.45 «J g−1 K−1» ✔

(d)

A voltaic cell is set up between the Fe2+ (aq) | Fe (s) and Fe3+ (aq) | Fe2+ (aq) half-cells.

Deduce the equation and the cell potential of the spontaneous reaction. Use section 24 of the data booklet.

[2]

Markscheme

Equation:
2Fe3+(aq) + Fe(s) → 3Fe2+(aq) ✔

Cell potential:
«+0.77 V − (−0.45 V) = +»1.22 «V» ✔


Do not accept reverse reaction or equilibrium arrow.

Do not accept negative value for M2.

(e)

The figure shows an apparatus that could be used to electroplate iron with zinc. Label the figure with the required substances.

[2]

Markscheme

left electrode/anode labelled zinc/Zn AND right electrode/cathode labelled iron/Fe ✔

electrolyte labelled as «aqueous» zinc salt/Zn2+ ✔


Accept an inert conductor for the anode.

Accept specific zinc salts such as ZnSO4.

(f)

Outline why, unlike typical transition metals, zinc compounds are not coloured.

[1]

Markscheme

« Zn2+» has a full d-shell
OR
does not form « ions with» an incomplete d-shell ✔


Do not accept “Zn is not a transition metal”.

Do not accept zinc atoms for zinc ions.

(g)

Transition metals like iron can form complex ions. Discuss the bonding between transition metals and their ligands in terms of acid-base theory.

[2]

Markscheme

ligands donate pairs of electrons to metal ions
OR
forms coordinate covalent/dative bond✔

ligands are Lewis bases
AND
metal «ions» are Lewis acids ✔

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