This question is about electrolysis.
A student investigated the following hypothesis:
'The electrolysis of any aqueous salt solution produces a gaseous non-metal at the negative electrode (cathode) and a halogen at the positive electrode (anode).'
What observation would be made at each electrode if the hypothesis is correct?
- Observation for gaseous non-metal at the negative electrode
- Observation for halogen at the positive electrode
Table 1 shows the student's results.
Table 1
| Aqueous Salt Solution | Product at the negative electrode | Product at the positive electrode |
|---|---|---|
| Sodium chloride | Hydrogen | Chlorine |
| Copper(II) sulfate | Copper | Oxygen |
| Potassium iodide | Hydrogen | Iodine |
Which salt solution in Table 1 does not support the student's hypothesis? Give a reason for your answer.
- Salt solution
- Reason
Platinum is used for the electrodes in some electrolysis experiments. Give two properties of platinum that make it suitable for this use.
A different student investigated the movement of ions during electrolysis using the apparatus shown in Figure 1.
The purple crystal of potassium manganate(VII) contains:
- colourless positive potassium ions (K+K^+K+)
- purple-coloured negative manganate(VII) ions (MnO4−\text{MnO}_4^-MnO4−).
The crystal dissolves in the electrolyte solution on the filter paper.
State and explain where the purple colour moves when the current is switched on.
- Movement of the purple colour
- Reason