1. 1
   An archaeologist studying ancient metalworking notes that gold objects have been found in their pure metallic form in riverbeds, requiring no chemical extraction, while iron tools from the same era show evidence that iron ore had to be heated with carbon to obtain the metal. Aluminium objects, however, do not appear at all until much later in history, once electricity-based extraction became available.

   (a)

   What does this pattern in the historical record mainly reflect?

   [1 mark]

   • AThe position of each metal in the reactivity series
   • BThe colour of each metal's ore
   • CThe density of each metal
   • DThe melting point of each metal only

   (b)

   Why could gold be found and used in its pure metallic form, unlike iron and aluminium?

   [1 mark]

   • AGold ore is found in much larger quantities than iron ore
   • BGold reacts readily with oxygen, so it is easily reduced from its ore
   • CGold has a very low melting point compared with iron and aluminium
   • DGold is very unreactive, so it exists naturally as the uncombined element

   (c)

   Explain why aluminium could not be extracted by early metalworkers using carbon, and had to wait for the development of electrolysis.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A steelworks operator is running a blast furnace to extract iron from haematite ore. Coke (carbon), limestone (calcium carbonate) and haematite (iron(III) oxide) are added at the top of the furnace, and hot air is blasted in near the bottom.

   (a)

   What is the main purpose of burning the coke with the hot air blast?

   [1 mark]

   • ATo decompose the limestone into calcium oxide
   • BTo directly reduce the iron(III) oxide to iron
   • CTo provide heat and produce carbon dioxide
   • DTo form the slag with silicon dioxide impurities

   (b)

   Which equation correctly represents the reduction of iron(III) oxide by carbon monoxide in the blast furnace?

   [1 mark]

   • AFe2O3 + 3C -> 2Fe + 3CO
   • BFe2O3 + 3CO -> 2Fe + 3CO2
   • C2Fe + 3CO2 -> Fe2O3 + 3CO
   • DFeO + CO -> Fe + CO2

   (c)

   Explain the role of the limestone added to the blast furnace, including what happens to it and how the resulting product removes impurities from the iron ore.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   An aluminium recycling company is considering building a new electrolysis plant to extract aluminium from bauxite ore instead of relying only on recycled scrap aluminium. Bauxite is purified to obtain aluminium oxide, which is then dissolved in molten cryolite before electrolysis.

   (a)

   State the main ore from which aluminium is extracted, and explain the purpose of dissolving the aluminium oxide in molten cryolite.

   [3 marks]

   (b)

   The plant engineers note that the carbon anodes used in the electrolysis cell need to be replaced regularly, unlike the cathode. Explain why the carbon anodes burn away over time, and write the ionic half-equation for the reaction occurring at the cathode.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A materials science teacher is designing a lesson to help students understand why different metals are extracted using different methods.

   (a)

   Using iron and aluminium as examples, discuss how the reactivity series determines the method of extraction used for each metal, describing the key reactions involved in the blast furnace extraction of iron from haematite, including the roles of coke, hot air, and limestone.

   [6 marks]

   (b)

   The teacher then asks students to explain the electrolytic extraction of aluminium from purified bauxite, for comparison with the blast furnace process. Describe the role of cryolite, the electrode reactions at the anode and cathode (including ionic half-equations), and explain why the carbon anodes require regular replacement.

   [6 marks]

   Total for question 4: 12 marks

End of questions