Question

Give appropriate scientific reasons for the following statements. During electrolysis of molten lead bromide graphite anode is preferred to other electrodes.

Answer 1

1. Graphite is act as an inert electrode in the electrolysis of molten lead bromide (${\mathrm{PbBr}}_2$) is preferred to other electrodes so that other active electrode does not react with bromine in the electrolytic solution.

2.Bromine ion will undergoes oxidation at anode by liberating bromine gas.

Chemical reaction occur as:

Lead bromide will dissociates into ${\mathrm{Pb}}^{2+},{\mathrm{Br}}^{-}$ ions on electrolysis.

$$\begin{gathered} {\mathrm{PbBr}}_2\rightleftharpoons {\mathrm{Pb}}^{2+}+2{\mathrm{Br}}^{-} \\ \left(\mathrm{Lead} \\ \mathrm{bromide}\right) \end{gathered}$$

At anode: Bromine gas is liberated.

$$\begin{gathered} \mathrm{Br}+{\mathrm{e}}^{-}\to {\mathrm{Br}}^{-} \\ \mathrm{Br}+\mathrm{Br}\to {\mathrm{Br}}_2 \\ \mathrm{bromine} \\ \mathrm{gas} \end{gathered}$$