Extraction and Uses of Metals
7 marks · HardThe metal iron is widely used in construction and manufacturing. Iron is typically extracted from its ore, haematite, which contains iron(III) oxide.
State what is meant by the term "ore".
Iron is found below carbon in the reactivity series.
Explain why carbon can be used to extract iron from its oxide, but cannot be used to extract aluminium from aluminium oxide.
Write a balanced chemical equation for the reduction of iron(III) oxide with carbon monoxide.
Suggest one economic reason why extraction by heating with carbon is preferred for some metals rather than extraction by electrolysis.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) An ore is a rock that contains enough of a mineral (or metal compound) for it to be worthwhile to extract the metal. · must show definition: ore = rock with enough mineral for extraction
(b) Carbon is above iron in the reactivity series, so it is more reactive and can displace iron from its oxide, reducing Fe2O3 to Fe. Aluminium is above carbon in the reactivity series, so carbon cannot displace aluminium from aluminium oxide; extraction must use electrolysis instead. · must show carbon more reactive than iron, carbon less reactive than aluminium, extraction method depends on reactivity
(c) · must show Fe2O3 + 3CO -> 2Fe + 3CO2, physical states optional
(d) Extraction by heating with carbon is cheaper than electrolysis because it uses less energy and does not require expensive electrical equipment. · must show lower energy cost with carbon, electrolysis is more expensive
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Defines 'ore' as a rock that contains enough mineral/metal to make extraction worthwhile
B2 (b) · 1 mark · States/reasons that carbon is more reactive than iron (or can reduce iron oxide) but less reactive than aluminium
B3 (b) · 1 mark · Explains that iron can be extracted by carbon reduction but aluminium must be extracted by electrolysis due to reactivity
B4 (c) · 1 mark · Writes correct formulae for reactants and products of the iron extraction equation (allow physical states omitted)
B5 (c) · 1 mark · Balances the equation correctly: Fe2O3 + 3CO -> 2Fe + 3CO2
B6 (d) · 1 mark · States that the carbon reduction method is cheaper than electrolysis / has lower energy costs
B7 (d) · 1 mark · Mentions that electrolysis requires expensive electrical equipment or high energy input
Worked solution
a) An ore is a rock or mineral that contains enough of a metal compound to make it economically worthwhile to extract the metal.
b) Carbon is more reactive than iron. It can reduce iron(III) oxide because it will remove the oxygen from the compound, leaving pure iron.
However, aluminium is more reactive than carbon, so carbon cannot reduce aluminium oxide to aluminium. Instead, aluminium must be extracted using electrolysis.
d) Extracting metals by heating with carbon is preferred, when possible, because it requires less energy and cheaper equipment compared to electrolysis, making it more cost-effective for large-scale production.