Iron is found in the Earth's crust as iron oxide ore. To extract iron, the ore is heated with carbon in a blast furnace. Explain why iron can be extracted using carbon, but gold does not need to be extracted this way.

Eduqas GCSE Chemistry — 2.3 Metals and their extraction · Explain · 4 marks · View as Markdown

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

Many metals are found in the Earth's crust as ores. The method used to extract a metal depends on its position in the reactivity series. Carbon can be used to extract some metals from their ores. Gold, however, is found as the pure metal in the Earth's crust.

Model answer (4 marks)

Iron is higher in the reactivity series than carbon, so carbon is more reactive than iron.
Carbon reduces iron(III) oxide in the blast furnace, displacing iron from the ore.
Gold is at the bottom of the reactivity series and is very unreactive.
Because gold does not react with other elements, it is found as the native metal in the crust and does not need to be extracted by reduction.

Examiner tips

  • Use the reactivity‑series hierarchy to justify carbon’s role. Show the displacement reaction (Fe₂O₃ + 3C → 2Fe + 3CO). State that gold is at the bottom of the series. Mention that gold is found as native metal.
  • common_mistakes
  • :
  • Confusing the positions of iron and carbon in the reactivity series. Claiming gold is reactive or that it requires reduction. Omitting the displacement/reduction step for iron.

Mark scheme (4 marks)

  1. Iron is more reactive than carbon / carbon is more reactive than iron
  2. Carbon displaces / reduces iron from its oxide ore
  3. Gold is (very) unreactive / gold is at the bottom of the reactivity series
  4. Gold does not react with other elements / gold is found uncombined (as the native metal) in the Earth's crust

Key terms in this question

ore

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