The electrolysis of sodium chloride solution
2 marks · NormalDuring the electrolysis of sodium chloride solution, hydrogen gas is produced at the cathode rather than sodium metal.
Explain why sodium ions do not gain electrons at the cathode, but hydrogen ions do.
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Also accept: Sodium is more reactive than hydrogen, so it is harder to reduce Na+ ions than H+ ions.; Hydrogen is less reactive than sodium so H+ ions are discharged in preference to Na+ ions at the cathode.
Common mistakes: Saying sodium collects at the cathode.; Saying hydrogen comes from sodium chloride.
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Marking points
M1 · 1 mark · States or implies that sodium is more reactive than hydrogen, or hydrogen is less reactive.
A1 · 1 mark · States that H+ ions are discharged/gain electrons in preference to Na+ ions because of their lower reactivity (or comparable formulation).
Worked solution
Sodium ions are not discharged because sodium is more reactive than hydrogen, so it is harder to reduce Na+ ions. Hydrogen ions are less reactive and so are discharged/gain electrons at the cathode instead.