Lithium hydride, LiH, is an ionic compound containing Li+\mathrm{Li^{+}}Li+ ions and hydride ions, H−\mathrm{H^{-}}H−. When molten lithium hydride is electrolysed, lithium forms at one electrode and hydrogen gas forms at the other.
Which half equation occurs at the anode, and what type of reaction is it?
2H++2e−→H2\mathrm{2H^{+} + 2e^{-} \rightarrow H_{2}}2H++2e−→H2, reduction
2H−+2e−→H2\mathrm{2H^{-} + 2e^{-} \rightarrow H_{2}}2H−+2e−→H2, reduction
Li++e−→Li\mathrm{Li^{+} + e^{-} \rightarrow Li}Li++e−→Li, reduction
2H−→H2+2e−\mathrm{2H^{-} \rightarrow H_{2} + 2e^{-}}2H−→H2+2e−, oxidation
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.