Extracting metals from their ores
5 marks · HardMagnesium and iron are both extracted from their ores, but by different methods.
State the method used to extract iron from its ore.
Explain, using the reactivity series, why this method can be used for iron but not for magnesium.
Name the method used to extract magnesium from its ore.
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(a) Reduction with carbon (or in a blast furnace)
(b) Iron is less reactive than carbon, so carbon can reduce iron(III) oxide to iron. Magnesium is more reactive than carbon, so carbon cannot reduce magnesium compounds. Therefore, a different method is needed for magnesium.
(c) Electrolysis
Common mistakes: Saying iron is extracted by electrolysis.; Saying magnesium can be extracted by reduction with carbon.
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Marking points
B1 (a) · 1 mark · States correct method for extracting iron (reduction with carbon or in a blast furnace).
M1 (b) · 1 mark · States that iron is less reactive than carbon (or is below carbon in the reactivity series).
M2 (b) · 1 mark · States that carbon can reduce iron(III) oxide but cannot reduce magnesium compounds.
A1 (b) · 1 mark · Links to why electrolysis is needed for magnesium—magnesium is more reactive than carbon.
B2 (c) · 1 mark · Names method for extracting magnesium as electrolysis.
Worked solution
a) Iron is extracted by reduction with carbon (in a blast furnace).
b) Iron is less reactive than carbon, so carbon can reduce iron(III) oxide by removing the oxygen to form iron metal. Magnesium is above carbon in the reactivity series, so it is more reactive than carbon. Carbon cannot reduce magnesium compounds, so a different method is needed.
c) Magnesium is extracted by electrolysis.