(a) A student was given two different types of electrodes (carbon and copper electrodes) to carry out electrolysis of copper(II) sulfate solution.
First, he carried out the experiment with carbon electrodes. At regular intervals, the cathode and anode were removed, dried and weighed. The results were plotted on the graph below.
(i) Give the formulae of the ions present in the electrolyte.
(ii) Explain why the cathode shows an increase in mass initially.
(iii) Describe what is observed at the anode with an appropriate equation.
(b) He carried out the same experiment with copper electrodes. Similarly, at regular intervals, the cathode and anode were removed, dried and weighed.
(i) Predict and draw on a separate graph how the mass of the anode and cathode will change as electrolysis occurs.
(ii) Explain how the graph for the anode is derived with a relevant equation.
(iii) The student noticed that the colour of the electrolyte remained the same as
electrolysis occurred. Explain what had taken place.