Question

Give the overall reaction for the electrolysis of molten Lead bromide

Answer 1

Part 1:- Reaction at the cathode:-

1. At cathode: ${\mathrm{Pb}}^{2+}\mathrm{ions}$ migrate toward the cathode.
2. They take two electrons each and become neutral lead atoms
3. $\underset{\mathrm{Lead}\mathrm{ions}}{{\mathrm{Pb}}^{2+}}+\underset{\mathrm{Electrons}}{2{\mathrm{e}}^{-}}\to \underset{\mathrm{Lead}}{\mathrm{Pb}}$

Part 2:- Reaction at the anode:-

1. At the anode: ${\mathrm{Br}}^{-}$ions migrate to the anode.
2. It gives an electrons and becomes bromide atom $\underset{\mathrm{Bromine}\mathrm{ions}}{{\mathrm{Br}}^{-}}+\underset{\mathrm{Electron}}{{\mathrm{e}}^{-}}\to \underset{\mathrm{Bromine}\mathrm{atom}}{\mathrm{Br}}$
3. Two bromine atoms combine to form the Bromine molecule. $\underset{\mathrm{Bromine}\mathrm{atom}}{\mathrm{Br}}+\underset{\mathrm{Bromine}\mathrm{atom}}{\mathrm{Br}}\to \underset{\mathrm{Bromine}\mathrm{molecule}}{{\mathrm{Br}}_2}$

Part 3: Overall reaction:-

1. $\underset{\mathrm{Molten}\mathrm{Lead}\mathrm{bromide}}{{\mathrm{PbBr}}_2\left(\mathrm{l}\right)}\stackrel{380°\mathrm{C}}{\to }\underset{\mathrm{Lead}}{\mathrm{Pb}\left(\mathrm{s}\right)(\mathrm{greyish}-\mathrm{white})}+\underset{\mathrm{Bromine}\mathrm{gas}}{{\mathrm{Br}}_2\left(\mathrm{g}\right)(\mathrm{dark}\mathrm{reddish}-\mathrm{brown})}$
2. Molten Lead bromide when electrolysed at $380°\mathrm{C}$ forms greyish-white metal of Lead at the cathode and dark reddish-brown fumes of Bromine gas at the anode.

Therefore, the overall reaction for the electrolysis of molten lead bromide is $\underset{\mathrm{Molten}\mathrm{Lead}\mathrm{bromide}}{{\mathrm{PbBr}}_2\left(\mathrm{l}\right)}\stackrel{380°\mathrm{C}}{\to }\underset{\mathrm{Lead}}{\mathrm{Pb}\left(\mathrm{s}\right)(\mathrm{greyish}-\mathrm{white})}+\underset{\mathrm{Bromine}\mathrm{gas}}{{\mathrm{Br}}_2\left(\mathrm{g}\right)(\mathrm{dark}\mathrm{reddish}-\mathrm{brown})}$