JAMB Chemistry 2015 Paper

Concept:In electrolysis using platinum electrodes, oxidation occurs at the anode.Explanation:Aqueous $\mathrm{CuSO}_4$ contains $\mathrm{Cu}^{2+}$, $\mathrm{SO}_4^{2-}$, $\mathrm{H}^+$ and $\mathrm{OH}^-$ ions.At the inert platinum anode, hydroxide ions are oxidized instead of sulfate ions.The balanced half-reaction for this oxidation is:$$4\mathrm{OH}^- \rightarrow 2\mathrm{H}_2\mathrm{O} + \mathrm{O}_2 + 4e^-$$Oxygen gas is liberated at the anode, while reduction of $\mathrm{Cu}^{2+}$ occurs at the cathode.This anode equation is represented by option B.Options A, C and D do not correctly show the oxidation reaction at the anode.Answer:Option B.