A student checks proposed electrode half equations involving Ca2+\mathrm{Ca^{2+}}Ca2+, Mg2+\mathrm{Mg^{2+}}Mg2+, Cl−\mathrm{Cl^{-}}Cl− and H+\mathrm{H^{+}}H+, with products Ca\mathrm{Ca}Ca, Mg\mathrm{Mg}Mg, Cl2\mathrm{Cl_{2}}Cl2 and H2\mathrm{H_{2}}H2.
Which half equation is balanced?
2Cl−→Cl2+e−\mathrm{2Cl^{-} \rightarrow Cl_{2} + e^{-}}2Cl−→Cl2+e−
4H++4e−→H2\mathrm{4H^{+} + 4e^{-} \rightarrow H_{2}}4H++4e−→H2
Mg2++e−→Mg\mathrm{Mg^{2+} + e^{-} \rightarrow Mg}Mg2++e−→Mg
Ca2++2e−→Ca\mathrm{Ca^{2+} + 2e^{-} \rightarrow Ca}Ca2++2e−→Ca
98 exam-style questions on OCR GCSE Chemistry 3.4 Electrolysis, covering 3.4.1 Products formed at the electrodes in electrolysis and 3.4.2 The technique of electrolysis. Each one has a worked solution and a mark scheme showing where the marks go.