1. 1
   A technician sets up an electrolysis cell using a solution of copper(II) sulfate, with two electrodes connected to a power supply. Copper is deposited at one of the electrodes.

   (a)

   At which electrode does the copper form?

   [1 mark]

   • AThe anode, because copper ions are negatively charged
   • BThe cathode, because copper ions gain electrons there
   • CThe anode, because copper ions lose electrons there
   • DThe cathode, because copper ions lose electrons there

   (b)

   Which half-equation correctly represents the reaction occurring at the electrode where copper is deposited?

   [1 mark]

   • ACu2+ + 2e- → Cu
   • BCu → Cu2+ + 2e-
   • C2Cl- → Cl2 + 2e-
   • DCu2+ - 2e- → Cu

   (c)

   State the material typically used for the electrodes in this process and explain why copper can be obtained from a solution of a copper salt by electrolysis.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A recycling company adds scrap iron directly to a large tank of copper(II) sulfate solution left over from an industrial process, without using any electricity. After some time, a reddish-brown solid appears on the iron.

   (a)

   What has happened?

   [1 mark]

   • AThe iron has simply dissolved without any reaction taking place
   • BCopper has displaced iron from the solution because copper is more reactive than iron
   • CIron has displaced copper from the solution because iron is more reactive than copper
   • DThe reddish-brown solid is iron oxide formed by rusting

   (b)

   In the reaction described above, what happens to the iron atoms as the reaction proceeds?

   [1 mark]

   • AIron atoms gain electrons and are reduced
   • BIron atoms gain electrons and are oxidised
   • CIron atoms neither gain nor lose electrons
   • DIron atoms lose electrons and are oxidised

   (c)

   Write the ionic equation for the reaction between iron and copper(II) sulfate solution, and explain the reaction in terms of oxidation and reduction.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student has two beakers of copper(II) sulfate solution recovered from a leachate produced by bioleaching. In Beaker 1, the student sets up electrolysis using inert electrodes connected to a power supply.

   (a)

   Describe what happens at each electrode during the electrolysis of the copper(II) sulfate solution in Beaker 1.

   [3 marks]

   (b)

   In Beaker 2, the student instead adds excess scrap iron filings directly to the copper(II) sulfate solution. Describe what happens in Beaker 2 and explain, in terms of reactivity, why this method also successfully extracts copper.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A mining company recovers a large volume of copper(II) sulfate leachate from bioleaching low-grade copper ore. The company must choose between extracting the copper by electrolysis or by displacement using scrap iron.

   (a)

   Explain, using ideas about electron transfer, how each method extracts copper from the leachate solution.

   [6 marks]

   (b)

   Evaluate the practical advantages and disadvantages of using displacement with scrap iron compared with electrolysis for extracting copper from this leachate solution on an industrial scale.

   [6 marks]

   Total for question 4: 12 marks

End of questions