A technician electrolyses zinc iodide using platinum electrodes connected to a d.c. power supply.
Electrolyte M is molten zinc iodide. Electrolyte A is zinc iodide dissolved in water.
Complete the table.
| Electrolyte | Ions present | Product at the negative electrode (cathode) | Product at the positive electrode (anode) |
|---|---|---|---|
| M | Zn2+\mathrm{Zn^{2+}}Zn2+ and I−\mathrm{I^-}I− | ...... | ...... |
| A | Zn2+\mathrm{Zn^{2+}}Zn2+, H+\mathrm{H^+}H+, I−\mathrm{I^-}I− and OH−\mathrm{OH^-}OH− | ...... | ...... |
Explain your predictions for the products at each electrode in electrolyte A.
Compare how charge is carried through molten zinc iodide and through the external wires.
In a separate experiment, a student electrolyses copper(II) sulfate solution using copper electrodes. The anode has a mass of 12.40 g before electrolysis and 12.10 g afterwards. The cathode has a mass of 10.25 g before electrolysis and 10.55 g afterwards.
What do the changes in mass show about what happens at each electrode?
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.