A technician electrolyses blue copper(II) sulfate solution using a graphite rod, P, and a pure copper plate, Q. The electrodes are connected to a direct current supply.
The technician washes, dries and weighs each electrode before and after the electrolysis.
| Electrode | Material | Mass before electrolysis in g | Mass after electrolysis in g |
|---|---|---|---|
| P | graphite | 32.84 | 33.48 |
| Q | pure copper | 46.15 | 45.51 |
Use the results to explain which electrode was connected to the positive terminal. Include the half equation for the reaction at this electrode.
Use the results to explain what happens to the blue colour of the solution during the electrolysis. Include the half equation for the reaction at P.
98 exam-style questions on OCR GCSE Chemistry 3.4 Electrolysis, covering 3.4.1 Products formed at the electrodes in electrolysis and 3.4.2 The technique of electrolysis. Each one has a worked solution and a mark scheme showing where the marks go.