Question

State the observations at the anode and at the cathode during the elecfrolysis of:
(i) fused lead bromide using graphite electrodes.
(ii) copper sulphate solution using copper electrodes.

Answer 1

(i) At the anode:
Dark reddish-brown fumes of bromine (gaseous state) evolve at the anode.

$2{\mathrm{Br}}^{-}\left(aq\right)-2e^{-}\to {\mathrm{Br}}_2\left(g\right)$

At the cathode:
Greyish white metal lead (liquid-state) is formed on the cathode.

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

(ii) At the anode:
Anode decreases in size due to the formation of copper (Cu) ions.

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

At the cathode:
Reddish-brown copper (Cu) is deposited.

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