Question

In the electrolysis of aqueous $CuBr_2$, using Pt electrodes, what are the products obtained at anode and cathode?

Answer 1

Cu at cathode, $Br_2$ at anode

Answer 2

Species in aqueous $CuBr_2$: $Cu^{2+}$, $Br^-$, $H_2O$. Pt electrodes are inert.

At cathode (reduction): Compare reduction potentials of $Cu^{2+}$ ($+0.34V$) and $H_2O$ ($-0.83V$). $Cu^{2+}$ is reduced as it has higher reduction potential. Cathode product: $Cu$.

At anode (oxidation): Compare reduction potentials of $Br_2/Br^-$ ($+1.09V$) and $O_2/H_2O$ ($+1.23V$). Species with lower reduction potential is oxidized. $Br^-$ is oxidized as $1.09V < 1.23V$. Anode product: $Br_2$.

Answer: Cu at cathode, $Br_2$ at anode.