1. 1
   A prospector pans through river sediment and finds small nuggets of pure gold metal, with no other elements chemically combined with it. Elsewhere, a mining company extracts iron from iron ore, which is found combined with oxygen as iron oxide, rather than as pure iron metal.

   (a)

   Which statement correctly explains why gold is found in the Earth as the uncombined element, unlike most other metals?

   [1 mark]

   • AGold is extremely unreactive, so it does not readily react with other elements in the environment to form compounds
   • BGold is extremely reactive, so it quickly reacts with everything around it to reform as pure metal
   • CGold is not actually a metal, which is why it is not found combined with other elements
   • DGold nuggets are artificially created by geological pressure rather than being a natural element

   (b)

   Elsewhere, a mining company extracts iron from iron ore, which is found combined with oxygen as iron oxide, rather than as pure iron metal, unlike the gold found by the prospector. Which statement correctly explains why iron, unlike gold, is found combined with other elements rather than as the pure metal?

   [1 mark]

   • AIron is less reactive than gold, so it exists only as compounds and never as the pure metal
   • BIron is more reactive than gold, so it readily reacts with oxygen and other elements in the environment to form compounds
   • CIron ore is a man-made material produced only during industrial mining
   • DIron does not actually contain any oxygen; iron oxide is a different substance entirely

   (c)

   Explain, in terms of reactivity, why gold is found in the Earth as the pure element while iron is found combined with oxygen as iron ore, and explain why iron ore must be chemically processed to obtain iron metal, unlike gold.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A steelworks extracts iron from iron oxide by heating it with carbon (in the form of coke) in a blast furnace. Meanwhile, a separate company extracts aluminium from aluminium oxide using electrolysis rather than heating it with carbon.

   (a)

   Which statement correctly describes the chemistry taking place in this process?

   [1 mark]

   • ACarbon reacts with iron metal directly, with no iron oxide involved at any point
   • BCarbon oxidises the iron oxide by adding more oxygen to it, producing a different iron compound
   • CCarbon reduces the iron oxide by removing oxygen from it, producing molten iron and carbon dioxide
   • DCarbon simply melts the iron oxide without any chemical reaction taking place

   (b)

   Meanwhile, a separate company extracts aluminium from aluminium oxide using electrolysis of the molten compound, rather than heating it with carbon, even though using carbon would in principle be a cheaper method. Which statement correctly explains why carbon cannot be used to extract aluminium from aluminium oxide?

   [1 mark]

   • ACarbon reacts explosively with aluminium oxide, making the process too dangerous
   • BAluminium is less reactive than carbon, so heating with carbon would work but is simply not used for historical reasons
   • CAluminium oxide does not contain any oxygen, so reduction is not possible
   • DAluminium is more reactive than carbon, so carbon is unable to remove the oxygen from aluminium oxide

   (c)

   Explain why iron can be extracted from iron oxide by reduction with carbon, but aluminium cannot be extracted from aluminium oxide in the same way, referring to the reactivity of each metal compared with carbon.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A metallurgy student is comparing the extraction of iron by reduction with carbon in a blast furnace with the extraction of aluminium by electrolysis of molten aluminium oxide. She notes that extracting aluminium uses far more electrical energy and is considerably more expensive per tonne of metal produced than extracting iron.

   (a)

   Write a word equation for the reduction of iron oxide by carbon in the blast furnace, and explain why this reduction method cannot be used to extract aluminium from aluminium oxide.

   [3 marks]

   (b)

   The student notes that extracting aluminium by electrolysis uses far more electrical energy and is considerably more expensive per tonne of metal produced than extracting iron by reduction with carbon. Explain why extracting aluminium by electrolysis requires so much more energy than extracting iron by reduction with carbon.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A metals engineer must decide on the correct extraction method for a newly discovered ore containing a metal that is less reactive than carbon. A second, separate ore is discovered containing a different metal that is more reactive than carbon.

   (a)

   Describe the general principle used to decide whether a metal should be extracted by reduction with carbon or by electrolysis, and describe, using the extraction of iron as an example, how reduction with carbon is carried out in practice.

   [6 marks]

   (b)

   A second, separate ore is discovered containing a different metal that is more reactive than carbon. Describe, using the extraction of aluminium as an example, why this metal must be extracted by electrolysis rather than by reduction with carbon, and explain the resulting economic and energy implications of using this method compared with the carbon reduction method used for iron.

   [6 marks]

   Total for question 4: 12 marks

End of questions