The electrolysis of sodium chloride solution
2 marks · EasyDescribe why the region near the cathode becomes alkaline during the electrolysis of sodium chloride solution.
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Hydrogen ions are discharged at the cathode as hydrogen gas, leaving hydroxide ions in the solution; these hydroxide ions build up, making the region alkaline.
Also accept: Hydroxide ions are left after hydrogen is produced, causing the solution to become alkaline.
Common mistakes: Hydrogen gas makes the solution alkaline.; Sodium ions make it alkaline.
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Marking points
B1 · 1 mark · States hydrogen ions are removed/discharged at the cathode.
B1 · 1 mark · Explains that hydroxide ions remain/increase, making the solution alkaline.
Worked solution
When hydrogen ions are discharged at the cathode, hydroxide ions are left behind in the solution. The increase in hydroxide ions causes the solution near the cathode to become alkaline.