Electrolysis may be used both to purify copper and to extract aluminium from an aluminium oxide / cryolite mixture. What reactions occur at the anode in each of these processes?
- APurification of copper: $\text{Cu}^{2+} + 2e^- \rightarrow \text{Cu}$; Extraction of aluminium: $2\text{O}^{2-} \rightarrow \text{O}_2 + 4e^-$
- BPurification of copper: $\text{Cu}^{2+} + 2e^- \rightarrow \text{Cu}$; Extraction of aluminium: $4\text{OH}^- \rightarrow \text{O}_2 + 2\text{H}_2\text{O} + 4e^-$
- CPurification of copper: $\text{Cu} \rightarrow \text{Cu}^{2+} + 2e^-$; Extraction of aluminium: $2\text{O}^{2-} \rightarrow \text{O}_2 + 4e^-$
- DPurification of copper: $\text{Cu} \rightarrow \text{Cu}^{2+} + 2e^-$; Extraction of aluminium: $4\text{OH}^- \rightarrow \text{O}_2 + 2\text{H}_2\text{O} + 4e^-$