Question

Electrolysis of KBr_(aq) gives Br₂ at anode but that of KF_(aq) does not give F₂. Give reason.

Answer 1

1. Oxidation takes place at the anode. The oxidation potential of Br⁻, H₂O, F⁻ are Br⁻ > H₂O > F⁻.
2. The higher the oxidation potential, the easier to oxidise. Therefore, in an aqueous solution of KBr, Br⁻ ions are oxidised to Br₂ in preference to H₂O.
3. On the other hand, in an aqueous solution of KF, H₂O is oxidised in preference to F⁻. Thus, in this case, oxidation of H₂O at the anode gives O₂ and no F₂ is produced.