Electrolysis and redox
2 marks · HardThe electrolysis of molten iron(III) chloride (FeCl₃) involves reactions at both electrodes.
State which electrode reaction involves oxidation, and which involves reduction. Explain your answer with reference to loss or gain of electrons.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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Oxidation occurs at the anode where chloride ions lose electrons. Reduction occurs at the cathode where iron(III) ions gain electrons.
Also accept: Oxidation is at the anode (chloride ions lose electrons). Reduction is at the cathode (iron(III) ions gain electrons).
Common mistakes: Stating oxidation occurs at cathode; Mixing up anode/cathode
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Marking points
B1 · 1 mark · Correctly identifies oxidation occurs at the anode and reduction at the cathode.
B2 · 1 mark · Correctly explains that oxidation is loss of electrons, reduction is gain of electrons, applied to ions at electrodes.
Worked solution
At the anode, chloride ions (Cl⁻) lose electrons to form chlorine gas, so this is oxidation (loss of electrons).
At the cathode, iron(III) ions (Fe³⁺) gain electrons to form iron metal, so this is reduction (gain of electrons).