1. 1
   A student places a clean iron nail into a test tube of blue copper sulfate solution. Over several minutes, the blue colour of the solution fades and a layer of brown-coloured solid forms on the surface of the nail. The student writes the ionic equation for the reaction: Fe(s) + Cu²⁺(aq) → Fe²⁺(aq) + Cu(s).

   (a)

   Which statement correctly explains this observation?

   [1 mark]

   • AIron is more reactive than copper, so it displaces copper from copper sulfate solution, forming iron sulfate solution and depositing copper metal
   • BCopper is more reactive than iron, so it displaces iron from the nail, forming copper sulfate and iron metal
   • CThe iron nail simply dissolves in the solution without any new substance being formed
   • DThe blue colour fades because the copper sulfate evaporates from the solution

   (b)

   The student writes the ionic equation for the reaction: Fe(s) + Cu²⁺(aq) → Fe²⁺(aq) + Cu(s). Which statement correctly describes what happens to the iron atoms during this reaction?

   [1 mark]

   • AThe iron atoms gain electrons to form Fe²⁺ ions, so iron is reduced
   • BThe iron atoms lose electrons to form Fe²⁺ ions, so iron is oxidised
   • CThe iron atoms neither lose nor gain electrons in this reaction
   • DThe iron atoms gain protons to become Fe²⁺ ions

   (c)

   Using the ionic equation Fe(s) + Cu²⁺(aq) → Fe²⁺(aq) + Cu(s), explain, in terms of oxidation and reduction, what happens to the iron and the copper ions during this displacement reaction.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A different student places a strip of zinc metal into a colourless solution of silver nitrate. Over time, silvery, crystal-like deposits form on the surface of the zinc strip, and the solution develops a faint blue-grey tinge. The overall ionic equation for the reaction is Zn(s) + 2Ag⁺(aq) → Zn²⁺(aq) + 2Ag(s).

   (a)

   Which statement correctly describes what is happening in this reaction?

   [1 mark]

   • AThe zinc strip is being coated with a layer of unreacted zinc oxide
   • BSilver is more reactive than zinc, so it displaces zinc from the zinc strip
   • CNo chemical reaction is taking place; the deposits are simply undissolved silver nitrate crystals
   • DZinc is more reactive than silver, so it displaces silver from silver nitrate solution, forming zinc nitrate solution and depositing silver metal

   (b)

   The overall ionic equation for the reaction is Zn(s) + 2Ag⁺(aq) → Zn²⁺(aq) + 2Ag(s). Which statement correctly describes what happens to the silver ions during this reaction?

   [1 mark]

   • AThe Ag⁺ ions are unchanged throughout the reaction
   • BThe Ag⁺ ions lose electrons to form silver atoms, so the silver ions are oxidised
   • CThe Ag⁺ ions gain electrons to form silver atoms, so the silver ions are reduced
   • DThe Ag⁺ ions gain protons to become silver atoms

   (c)

   Using the ionic equation Zn(s) + 2Ag⁺(aq) → Zn²⁺(aq) + 2Ag(s), explain what this reaction shows about the relative positions of zinc and silver in the reactivity series, and identify which species is oxidised and which is reduced.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A technician sets up an experiment adding small samples of magnesium metal to three separate test tubes containing solutions of copper sulfate, zinc sulfate and calcium sulfate. She observes that a brown coating forms on the magnesium in the copper sulfate solution and a grey coating forms on the magnesium in the zinc sulfate solution, but no visible reaction occurs in the calcium sulfate solution. She then carries out one further displacement test.

   (a)

   Explain what these results show about the relative reactivity of magnesium, copper, zinc and calcium, and write the ionic equation for the reaction between magnesium and copper sulfate solution.

   [3 marks]

   (b)

   The technician adds a piece of zinc metal to a test tube of copper sulfate solution. A brown solid forms on the zinc and the blue colour of the solution fades. Explain, using ideas of oxidation and reduction, what happens to the zinc atoms and the copper ions in this displacement reaction, and explain why this result is consistent with the earlier experiment.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A recycling company recovers copper metal from a dilute copper sulfate waste solution by adding scrap iron to the solution, causing copper to be deposited as a solid, which is then filtered out and collected. The company considers, but rejects, using scrap silver instead of scrap iron for this process.

   (a)

   Describe, in terms of the reactivity series and oxidation and reduction, how this displacement reaction allows copper to be recovered from the solution, including the ionic equation for the reaction.

   [6 marks]

   (b)

   The company considers, but rejects, using scrap silver instead of scrap iron to recover copper from the same copper sulfate solution. Explain, in terms of the reactivity series and oxidation and reduction, why using silver instead of iron would not work to recover copper from the solution.

   [6 marks]

   Total for question 4: 12 marks

End of questions