Describe how iron is extracted from its ore in a blast furnace. Include the role of coke and limestone in the process.

Cambridge International IGCSE Chemistry (0620) — 9.6 Extraction of metals · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Coke is introduced into the blast furnace and burns in the hot air blast, forming carbon dioxide. The carbon dioxide reacts with additional coke (or carbon) to produce carbon monoxide. This carbon monoxide then reduces the iron oxide ore to iron metal. Limestone is also added; it decomposes to calcium oxide, which reacts with acidic impurities such as silicon dioxide to form slag (calcium silicate).

Examiner tips

Use the exact terms: coke, carbon dioxide, carbon monoxide, limestone, calcium oxide, slag, calcium silicate.
Show the sequence: burning, reduction, slag formation.
Mention the role of each component clearly.
Keep the answer concise to fit the 4‑mark limit.

Common mistakes

Confusing carbon dioxide with carbon monoxide as the reducing agent.
Omitting the role of limestone or slag formation.
Using vague terms like ‘fuel’ instead of ‘coke’.

Mark scheme (4 marks)

Coke burns in the blast of hot air to produce carbon dioxide / coke reacts with oxygen to produce carbon dioxide
Carbon dioxide reacts with more coke/carbon to form carbon monoxide
Carbon monoxide reduces iron oxide / iron ore to iron
Limestone decomposes to form calcium oxide, which reacts with acidic impurities / silicon dioxide to form slag (calcium silicate)

Key terms in this question

blast furnace · coke · limestone