Question

State one relevant observation for each of the following

At the anode, when molten Lead bromide is electrolyzed using graphite electrodes.

Answer 1

Observation at the anode:-

1. The ${\mathrm{Br}}^{-}\mathrm{ions}$ migrate towards the anode.
2. It gives an electron and thus becomes bromine atom.
3. Then two bromine atoms combine together to form the Bromine molecule.
4. $$\begin{gathered} \underset{\mathrm{Bromine}\mathrm{ion}}{{\mathrm{Br}}^{-}\left(\mathrm{l}\right)}\to \underset{\mathrm{Bromine}\mathrm{atom}}{\mathrm{Br}}+\underset{\mathrm{Electron}}{{\mathrm{e}}^{-}} \\ \underset{\mathrm{Bromine}\mathrm{atom}}{\mathrm{Br}}+\underset{\mathrm{Bromine}\mathrm{atom}}{\mathrm{Br}}\to \underset{\mathrm{Bromine}\mathrm{gas}}{{\mathrm{Br}}_2(\uparrow )\left(\mathrm{g}\right)(\mathrm{brown}\mathrm{fumes})} \end{gathered}$$
5. Bromine gas is evolved at the anode in form of brown fumes

Therefore, at the anode, when molten lead bromide is electrolysed using graphite electrodes, Bromine gas is evolved in the form of brown fumes.