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3 marksElectrochemistry

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

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.

Plot a graph of actual mass of copper deposited versus time using the axes in Figure 1 on page 5.

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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)(vi)Use the graph to predict the mass of copper that would be deposited after 28 minutes.[1 mark]
  6. 1(a)(vii)Write an ionic equation to represent the reaction at the cathode.[2 marks]
  7. 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]
  8. 1(a)(ix)Calculate the number of moles of copper that would be formed.[2 marks]
  9. 1(a)(x)Calculate the mass of copper that would be formed. (Relative atomic mass: Cu = 64; 1 F = 96 500 C)[1 mark]
  10. 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]
  11. 1(a)(xii)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…[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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