What is the ionic half-equation for the reaction taking place at the cathode when molten lead(II) bromide is electrolysed?
- A$\text{Pb}^{2+} + 2e^- \rightarrow \text{Pb}$
- B$2\text{Br}^- \rightarrow \text{Br}_2 + 2e^-$
- C$\text{Br}_2 + 2e^- \rightarrow 2\text{Br}^-$
- D$\text{Pb} \rightarrow \text{Pb}^{2+} + 2e^-$