Molten iron oxide, Fe2O3\mathrm{Fe_{2}O_{3}}Fe2O3, is electrolysed using inert electrodes. It is an ionic compound. Iron forms at the cathode and oxygen gas forms at the anode.
Which row gives the correct cathode half equation and the amount of oxygen gas formed for every 4 moles of iron formed?
Fe3++3e−→Fe\mathrm{Fe^{3+} + 3e^{-} \rightarrow Fe}Fe3++3e−→Fe; 3 moles of oxygen gas
Fe3++3e−→Fe\mathrm{Fe^{3+} + 3e^{-} \rightarrow Fe}Fe3++3e−→Fe; 6 moles of oxygen gas
Fe2++2e−→Fe\mathrm{Fe^{2+} + 2e^{-} \rightarrow Fe}Fe2++2e−→Fe; 2 moles of oxygen gas
Fe3+→Fe+3e−\mathrm{Fe^{3+} \rightarrow Fe + 3e^{-}}Fe3+→Fe+3e−; 3 moles of oxygen gas
52 exam-style questions on Edexcel GCSE Chemistry 4.2 Electrolytic processes, covering 4.2.1 Electrolytes and the process of electrolysis, 4.2.2 Products of electrolysis using inert electrodes, 4.2.3 Half equations, oxidation and reduction in electrolysis, and 4.2.4 Electrolysis of copper sulfate and purifying copper. Each one has a worked solution and a mark scheme showing where the marks go.