The electrolysis of molten compounds

2 marks · Normal

Write the half-equation for the reaction at the cathode during the electrolysis of molten zinc chloride (ZnCl_2). State what is observed at the cathode.

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Zn^{2+} + 2e^- → Zn; grey zinc metal forms.

Also accept: Zinc deposited at the cathode; metallic zinc forms; Zn2+ + 2e- → Zn

Common mistakes: Omitting electrons/proper balancing; Mixing up cathode/anode products

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Marking points

B1 · 1 mark · Correct cathode half-equation: Zn^{2+} + 2e^- → Zn

B2 · 1 mark · States grey zinc metal is formed at the cathode

Worked solution

At the cathode: Zn^{2+} ions gain 2 electrons to form zinc metal.

Observation: Grey zinc metal deposits at the cathode.