Question

State the observations at the anode and at the cathode during electrolysis of:

fused lead bromide using graphite electrodes

Answer 1

Electrolysis of fused Lead bromide $\left({\mathrm{PbBr}}_2\right)$ using graphite electrodes

• Electrolysis of Lead bromide is carried out by heating solid Lead bromide in a silica crucible.

Observations at cathode:

• The positively charged ${\mathrm{Pb}}^{2+}$ ions are discharged at the cathode, where these ions are converted into metallic lead by accepting electrons from the cathode.
• Grey deposition of Lead is observed at the cathode.
• Reaction at the cathode is depicted below.

${\mathrm{Pb}}^{2+}\left(\mathrm{aq}\right)+2{\mathrm{e}}^{-}\to \mathrm{Pb}\left(\mathrm{s}\right)$

Observations at anode:

• The negatively charged ${\mathrm{Br}}^{-}$ ions are discharged at the anode, where these ions lose electrons to produce neutral bromine atoms.
• The bromine atoms then combine to form bromine molecules by forming a covalent bond between them.
• The reddish-brown vapor of ${\mathrm{Br}}_2$ is liberated at the anode.
• Reactions at the anode are depicted below.

$$\begin{gathered} \left[{\mathrm{Br}}^{-}\right(\mathrm{aq})-{\mathrm{e}}^{-}\to \mathrm{Br}]\times 2\left(\mathrm{atom}\right) \\ \mathrm{Br}+\mathrm{Br}\to {\mathrm{Br}}_2\left(\mathrm{g}\right)\left(\mathrm{molecule}\right) \end{gathered}$$