Extraction and Uses of Metals
8 marks · HardZinc and iron are both important metals found in the Earth's crust, but they are extracted by slightly different methods due to their positions in the reactivity series.
Define the term 'ore' and name a metal often found native (uncombined) in the Earth's crust.
Explain why zinc and iron can both be extracted from their oxides by heating with carbon, but aluminium cannot.
Write a balanced equation for the reduction of iron(III) oxide using carbon monoxide in the blast furnace.
State one economic factor that affects the choice of extraction method for a metal and explain why it is important.
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.
Show answer
(a) An ore is a rock that contains enough of a mineral for it to be worthwhile to extract the metal. Gold is a metal often found native.
(b) Zinc and iron are below carbon in the reactivity series so can be reduced by carbon; aluminium is above carbon and cannot be reduced this way.
(c)
(d) Cost of energy is important; cheaper methods are preferred to reduce the overall production cost of the metal.
Common mistakes: Confusing 'ore' and 'mineral'; Incorrectly naming metals found native; Incorrect formulae for iron(III) oxide and CO; Leaving out economic explanation
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States a correct definition of an ore.
B2 (a) · 1 mark · Names a metal often found native (uncombined), e.g. gold.
B3 (b) · 1 mark · States that zinc/iron can be reduced/extracted by carbon but aluminium cannot.
B4 (b) · 1 mark · Refers to relative positions in the reactivity series (zinc/iron below, aluminium above carbon).
B5 (c) · 2 marks · Correctly writes a balanced chemical equation for iron(III) oxide reduction by CO: . (2 marks all correct, 1 mark if one error only in formula or balancing/manufacturing error)
B6 (d) · 1 mark · States a correct economic factor affecting extraction (e.g. cost of energy, cost of reducing agent).
B7 (d) · 1 mark · Explains why this factor is important (e.g. lower cost makes extraction more economical) or gives a consequence (e.g. raises overall cost).
Worked solution
a) An ore is a type of rock that contains enough of a mineral for it to be worthwhile to extract the metal from it.
Gold is a metal that is often found native (uncombined) in the Earth's crust. Other examples include platinum and sometimes silver.
b) Zinc and iron can both be extracted from their oxides by heating with carbon because they are less reactive than carbon, so carbon can remove the oxygen from their oxides. Aluminium is more reactive than carbon and cannot be extracted in this way; it requires electrolysis.
c) The balanced chemical equation for the reduction of iron(III) oxide by carbon monoxide is:
d) One economic factor is the cost of energy. The extraction process should use the least amount of energy possible to keep the production cost of the metal low. Cheaper methods make the extraction more economically viable.