4.3 Extracting metals with carbon
5 exam questions worth 9 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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Why is gold found in the Earth as the metal itself?
Choose one answer.
Correct Not quite: the answer is It is very unreactive
Mark scheme
B
Model answer
B: gold is very unreactive, so it does not form compounds easily.
Explain why iron can be extracted from iron oxide by heating with carbon.
Mark scheme
- carbon is more reactive than iron (1)
- so carbon removes the oxygen / reduces the iron oxide (1)
Model answer
Carbon is more reactive than iron, so it takes the oxygen from iron oxide, reducing it to iron.
Explain why aluminium is extracted by electrolysis, not by heating with carbon.
Mark scheme
- aluminium is more reactive than carbon (1)
- so carbon cannot reduce aluminium oxide (1)
Model answer
Aluminium is above carbon in the reactivity series, so carbon cannot remove the oxygen from aluminium oxide.
Lead oxide, PbO, is heated with carbon to produce lead and carbon dioxide.
Write a balanced equation for this reaction.
Mark scheme
- correct formulae PbO, C, Pb, CO2 (1)
- 2PbO + C → 2Pb + CO2 (1)
Model answer
2PbO + C → 2Pb + CO2
Suggest why extracting metals by electrolysis is more expensive than extracting them with carbon.
Mark scheme
- electrolysis uses large amounts of electricity / energy (1)
- energy also needed to melt the compound (1)
Model answer
Electrolysis needs huge amounts of electricity, and energy is also needed to melt the ore, whereas carbon is cheap.
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