Chemistry›Extraction of Metals
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C9 Chemistry of AtmAQA GCSE Chemistry · 8462 (Triple)

Extraction of Metals

Reactivity series, methods of extraction, reduction with carbon, electrolysis for reactive metals.

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CognitoExtraction of metals — reduction and electrolysis
Key facts & methods

Reactivity and extraction

  • Metals occur naturally as ores (compounds in rock) or, rarely, as native elements (gold, platinum).
  • The method of extraction depends on the metal reactivity.
  • Less reactive than carbon: extracted by reduction with carbon (cheaper). E.g. iron, zinc, copper, lead.
  • More reactive than carbon: extracted by electrolysis (expensive — needs electrical energy). E.g. aluminium, sodium, calcium.
  • Gold and platinum found uncombined — no extraction needed.

Reduction with carbon (e.g. iron in blast furnace)

  • Iron ore (Fe2O3) + carbon → iron + CO2.
  • Carbon removes oxygen from iron oxide — this is reduction. Carbon is oxidised to CO2.
  • Blast furnace: iron ore + coke (carbon) + limestone → molten iron + slag.
  • Limestone removes impurities as slag (calcium silicate).
  • Pig iron from blast furnace contains ~4% carbon → made into steel by removing excess carbon.

Electrolysis of aluminium

  • Aluminium is too reactive to reduce with carbon — electrolysis is used.
  • Aluminium ore (bauxite) → purified to aluminium oxide (Al2O3).
  • Al2O3 dissolved in molten cryolite (lowers melting point).
  • Electrolysis: Al3+ reduced at cathode → Al. O2- oxidised at anode → O2.
  • Carbon anodes burn away in the oxygen — must be replaced regularly.
  • High energy cost makes aluminium expensive — recycling is much cheaper.

Redox in extraction

  • Extraction of metals involves REDOX reactions.
  • Reduction: metal ion gains electrons → becomes metal.
  • Oxidation: reducing agent (carbon, hydrogen, or electrolysis) loses electrons.
  • OIL RIG: Oxidation Is Loss (of electrons), Reduction Is Gain (of electrons).
  • Electrolysis: metal deposits at cathode (gains electrons). Non-metal produced at anode (loses electrons).
Exam questions — 4 questions · 10 marks · AQA 8462 style
⚡ Show all working — the AI marks against the AQA mark scheme. Method marks awarded for correct working even if the final answer is wrong.
1 markExtraction methodAQA 8462 style

Why is aluminium extracted by electrolysis rather than by reduction with carbon?

A Aluminium is cheaper to extract using electricity
B Aluminium is more reactive than carbon, so carbon cannot reduce aluminium ions
C Carbon reacts with aluminium to form a dangerous compound
D Aluminium does not form an oxide
3 marksBlast furnace reductionAQA 8462 style

In the blast furnace, iron is extracted from iron(III) oxide (Fe2O3) using carbon. Write a word equation and identify which substance is oxidised and which is reduced. (3 marks)

Hint: Word equation: oxide + carbon → metal + CO2. Then identify reduction (metal gains, loses O) and oxidation (carbon gains O). Use OIL RIG.
+30 XP
1 markNative metalsAQA 8462 style

Why is gold found naturally as a pure metal rather than as an ore?

A Gold does not form compounds
B Gold is very unreactive and so does not readily form compounds with other elements
C Gold is too heavy to mix with other elements in rock
D Gold ores decompose spontaneously into pure gold
4 marksElectrolysis of aluminium oxideAQA 8462 style

Describe the electrolysis of aluminium oxide to produce aluminium. Include what happens at each electrode and explain why cryolite is used. (4 marks)

Hint: Cover: cryolite purpose (lower MP), cathode reaction (Al3+ → Al, reduction), anode reaction (O2- → O2, oxidation), why carbon anodes need replacing.
+40 XP

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