A student investigates the extraction of metals from their oxides by heating each oxide with carbon. Copper oxide, zinc oxide and magnesium oxide are each heated separately with excess carbon. State which oxides are reduced by carbon and, for each case, explain why carbon is or is not able to reduce the oxide. Include the role of carbon as a reducing agent in your answer.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
In the reactivity series, the order from most to least reactive is: magnesium, zinc, carbon, copper.
Model answer (4 marks)
Copper oxide is reduced by carbon – copper is extracted by reduction with carbon.
Zinc oxide is reduced by carbon – zinc is extracted by reduction with carbon.
Magnesium oxide is not reduced by carbon because magnesium is more reactive than carbon.
Carbon acts as a reducing agent by removing oxygen from the metal oxide; carbon itself is oxidised (gains oxygen) during the reaction.
Zinc oxide is reduced by carbon – zinc is extracted by reduction with carbon.
Magnesium oxide is not reduced by carbon because magnesium is more reactive than carbon.
Carbon acts as a reducing agent by removing oxygen from the metal oxide; carbon itself is oxidised (gains oxygen) during the reaction.
Examiner tips
- Use the word ‘reduced’ and ‘extract’ to show understanding of the process.
- Mention the relative reactivity of Mg and C to justify why MgO is not reduced.
- Explain the role of carbon as a reducing agent – it loses electrons (is oxidised).
Common mistakes
- Saying that all oxides are reduced by carbon – ignores MgO’s resistance.
- Confusing ‘more reactive than’ with ‘more easily reduced’ – must state Mg > C in reactivity series.
Mark scheme (4 marks)
- Copper oxide is reduced by carbon / copper is extracted by reduction with carbon
- Zinc oxide is reduced by carbon / zinc can be extracted by reduction with carbon
- Magnesium oxide is NOT reduced by carbon because magnesium is more reactive than carbon
- Carbon acts as a reducing agent by removing oxygen from the metal oxide / carbon itself is oxidised (gains oxygen) during the reaction
Key terms in this question
Related
- All Pearson Edexcel International GCSE Chemistry (4CH1) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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