During the electrolysis of an aqueous solution such as sodium sulfate, hydroxide ions (OH−\text{OH}^-OH−) are discharged at the anode to produce oxygen gas and water. Which of the following represents the correctly balanced half-equation for this oxidation reaction?
4OH−→O2+2H2O−4e−4\text{OH}^- \rightarrow \text{O}_2 + 2\text{H}_2\text{O} - 4\text{e}^-4OH−→O2+2H2O−4e−
4OH−−4e−→O2+2H2O4\text{OH}^- - 4\text{e}^- \rightarrow \text{O}_2 + 2\text{H}_2\text{O}4OH−−4e−→O2+2H2O
2OH−−2e−→O2+H22\text{OH}^- - 2\text{e}^- \rightarrow \text{O}_2 + \text{H}_22OH−−2e−→O2+H2
4OH−−2e−→O2+2H2O4\text{OH}^- - 2\text{e}^- \rightarrow \text{O}_2 + 2\text{H}_2\text{O}4OH−−2e−→O2+2H2O
34 exam-style questions on OCR GCSE Chemistry Electrolysis. Each one has a worked solution and a mark scheme showing where the marks go.