A student electrolyses four solutions, W, X, Y and Z, using inert electrodes.
The table shows the student's observations.
| Solution | Observations at the cathode (−) | Observations at the anode (+) |
|---|---|---|
| W: copper(II) chloride | a pink-brown solid forms | bubbles of a pale green gas form |
| X: potassium sulfate | bubbles of a colourless gas form | bubbles of a colourless gas form |
| Y: silver nitrate | a shiny grey solid forms | bubbles of a colourless gas form |
| Z: sodium iodide | bubbles of a colourless gas form | the solution around the electrode turns brown |
Identify the product at each electrode for each solution.
Explain why each product forms, using ideas about the ions present in each solution. Include half equations in your answer.
In solution X, the volume of gas collected at the cathode is twice the volume of gas collected at the anode.
Use half equations to explain why.
52 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.