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Date May 2021 Marks available 1 Reference code 21M.2.sl.TZ1.3
Level SL Paper 2 Time zone TZ1
Command term Determine Question number 3 Adapted from N/A

Question

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

Iron exists as several isotopes.

In acidic solution, hydrogen peroxide, H2O2, will oxidize Fe2+.

Fe2+ (aq) → Fe3+ (aq) + e

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

[1]
a.

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

[1]
b(i).

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

[2]
b(ii).

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]
c.

Write the half-equation for the reduction of hydrogen peroxide to water in acidic solution.

[1]
d(i).

Deduce a balanced equation for the oxidation of Fe2+ by acidified hydrogen peroxide.

[1]
d(ii).

Markscheme

1:2 ✔

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

a.

mass «spectroscopy»/MS ✔

b(i).

Award [1 max] for 4 correct values.

b(ii).

specific heat capacity « = qm×T/1000J50g×44K» = 0.45 «J g−1 K−1» ✔

c.

H2O2(aq) + 2H+(aq) + 2e→ 2H2O(l) ✔

d(i).

H2O2(aq) + 2H+(aq) + 2Fe2+(aq) → 2H2O(l) + 2Fe3+(aq) ✔

d(ii).

Examiners report

[N/A]
a.
[N/A]
b(i).
[N/A]
b(ii).
[N/A]
c.
[N/A]
d(i).
[N/A]
d(ii).

Syllabus sections

Core » Topic 5: Energetics/thermochemistry » 5.1 Measuring energy changes
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