Extraction and Uses of Metals
7 marks · HardIron is an important metal, widely used in construction and engineering. It is extracted from its ore, haematite, in the blast furnace.
State what is meant by an ore.
Explain why iron can be extracted from its oxide by heating with carbon, but aluminium cannot be extracted from its oxide by heating with carbon.
Write a balanced chemical equation for the extraction of iron from iron(III) oxide using carbon monoxide as the reducing agent.
Describe, in terms of redox, what happens to iron(III) oxide in the blast furnace when it reacts with carbon monoxide.
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) A rock containing enough of a mineral (metal compound) for it to be worthwhile to extract the metal.
(b) Iron is below carbon in the reactivity series, so carbon is more reactive and can reduce iron(III) oxide; aluminium is above carbon, so carbon cannot reduce aluminium oxide.
(c) · must show Balanced chemical equation with correct formulae and state symbols.
(d) Iron(III) oxide is reduced (loses oxygen) to form iron; carbon monoxide is oxidised to carbon dioxide. · must show Explanation must refer to loss of oxygen or gain of electrons for reduction.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Defines an ore as a rock/mineral containing enough of the metal for extraction to be worthwhile.
B1 (b) · 1 mark · States iron is below carbon in reactivity series and can be reduced by carbon.
B1 (b) · 1 mark · States aluminium is above carbon and cannot be reduced by carbon, or only extractable by electrolysis.
B1 (c) · 2 marks · 1 mark for correct reactants and products; 1 mark for a fully balanced equation with correct state symbols.
B1 (d) · 1 mark · States iron(III) oxide is reduced (gains electrons/loses oxygen).
B1 (d) · 1 mark · States carbon monoxide is oxidised (loses electrons/gains oxygen) or links redox to oxygen transfer/electron movement.
Worked solution
a) An ore is a rock or mineral that contains enough of a metal compound to make it economically worthwhile extracting the metal.
b) Iron can be extracted using carbon because iron is below carbon in the reactivity series; carbon is more reactive than iron and can remove oxygen from iron oxide. Aluminium is above carbon in the reactivity series, so carbon is not reactive enough to reduce aluminium oxide; therefore, aluminium must be extracted using electrolysis.
d) When iron(III) oxide reacts with carbon monoxide in the blast furnace, iron(III) oxide is reduced as it loses oxygen atoms and forms iron. At the same time, carbon monoxide is oxidised as it gains oxygen and forms carbon dioxide. This is a redox reaction: reduction is loss of oxygen (iron(III) oxide to iron) and oxidation is gain of oxygen (carbon monoxide to carbon dioxide).