Impure copper is refined by electrolysis. The electrolyte in this method is aqueous copper(II) sulfate. Which reaction occurs at the anode?
- A$\text{Cu}(s) \rightarrow \text{Cu}^{2+}(aq) + 2e^-$
- B$\text{Cu}^{2+}(aq) + 2e^- \rightarrow \text{Cu}(s)$
- C$2\text{OH}^-(aq) \rightarrow \tfrac{1}{2}\text{O}_2(g) + \text{H}_2\text{O}(l) + 2e^-$
- D$2\text{H}_2\text{O}(l) + 2e^- \rightarrow \text{H}_2(g) + 2\text{OH}^-(aq)$