Extraction of Metals

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CognitoExtraction of metals — reduction and electrolysis

Key facts & methods

Reactivity and extraction — fill in the table

Method	When used	Examples
Reduction with carbon
Electrolysis
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 — fill in the table

Term	Definition
Reduction
Oxidation
OIL RIG
Electrolysis

Exam questions — 4 questions · 10 marks · AQA 8462 style

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

Quick recall flashcards

Extraction of Metals

Reactivity and extraction — fill in the table

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

Electrolysis of aluminium

Redox in extraction — fill in the table

Module complete! 🎉