Question

Write the equations for the reactions, which take place at the electrodes during the electrolysis of lead bromide.

Answer 1

The ions present in molten lead bromide are lead cations and bromide anions:
$$\begin{gathered} {\mathrm{PbBr}}_2\stackrel{}{\to }{\mathrm{Pb}}^{2+}+2{\mathrm{Br}}^{-} \\ \mathrm{Lead}\mathrm{b}\mathrm{romide}\mathrm{Lead}\mathrm{cation}\mathrm{Bromide}\mathrm{a}\mathrm{nion} \end{gathered}$$

Reaction at cathode - Positively charged lead ions get discharged at the negative electrode (cathode). Lead ions recieve two electrons from cathode and is reduced to lead metal. Thus the cathode is coated with a thin grey coat of lead metal. Reduction reaction can be written as:
${\mathrm{Pb}}^{2+}+2{\mathrm{e}}^{-}\stackrel{}{\to }\mathrm{Pb}(\mathrm{lead}\mathrm{metal})$

Reaction at anode - Negatively charged bromide ions get discharged at positive electrode (anode). Bromide ion lose an electron to anode and is oxidised to bromine atom, two bromine atoms combine together to form red vapours of bromine gas at anode. Oxidation reaction can be written as:
$2{\mathrm{Br}}^{-}\stackrel{}{\to }{\mathrm{Br}}_2+2{\mathrm{e}}^{-}$