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1 markElectrochemistry

CSEC Chemistry · May/June 2011 · Paper 2 · Question 1(a)(xii)

Students investigated the electrolysis of copper(II) sulphate using copper electrodes. They measured the mass of the copper cathode at five-minute intervals after passing a 0.2 A current. Table 1 shows the initial mass and masses for some readings.

The circuit used in this experiment was modified by replacing the copper electrodes with graphite electrodes. State ONE difference in the reaction at the anode when graphite electrodes are used.

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Other parts of this question

  1. 1(a)(i)Define the term 'electrolysis'.[2 marks]
  2. 1(a)(ii)State TWO differences between the 'anode' and the 'cathode'.[2 marks]
  3. 1(a)(iii)Draw a diagram to show a circuit for carrying out this investigation. Label the cathode and the electrolyte.[3 marks]
  4. 1(a)(iv)Complete Table 1 by recording the mass of the cathode after 10 minutes and 20 minutes and the mass of copper deposited after 15 and 25 minutes.[2 marks]
  5. 1(a)(v)Plot a graph of actual mass of copper deposited versus time using the axes in Figure 1 on page 5.[3 marks]
  6. 1(a)(vi)Use the graph to predict the mass of copper that would be deposited after 28 minutes.[1 mark]
  7. 1(a)(vii)Write an ionic equation to represent the reaction at the cathode.[2 marks]
  8. 1(a)(viii)Calculate the quantity of electricity that passed through the copper sulphate solution when 0.2 A of current flowed for 20 minutes. (Quantity of electricity =…[2 marks]
  9. 1(a)(ix)Calculate the number of moles of copper that would be formed.[2 marks]
  10. 1(a)(x)Calculate the mass of copper that would be formed. (Relative atomic mass: Cu = 64; 1 F = 96 500 C)[1 mark]
  11. 1(a)(xi)Suggest a reason for the difference between the mass of copper obtained in (x) above and that recorded in Table 1.[1 mark]
  12. 1(b)Complete Table 2 by writing the observations for the tests carried out on Salt S.[3 marks]

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