ICSE Class 10 Answered

Electrolyte: Molten lead bromide (PbBr₂)

Electrodes:

Anode: Graphite

Cathode: Graphite

Ions present:

Pb²⁺ and Br^– 

Overall reaction:                    PbBr₂ → Pb²⁺ + 2Br^– 

Electrode reactions: 

Reaction at the cathode:        Pb²⁺ + 2e⁻ →   Pb

Reaction at the anode:           Br– −  e⁻   →  Br

                                                Br + Br →  Br₂

• Electrolysis of Acidified Water

Electrodes:

Anode: Platinum

Cathode: Platinum

Ionisation of acidified water: H₂O 

Electrodes:

Anode: Platinum

Cathode: Platinum

Ionisation of acidified water:  

Ions present: H⁺, SO₄^2–, OH^–

Electrode reactions: 

Reaction at the cathode: H+ + e⁻   →  H

                                         H + H → H₂  (hydrogen molecule)

Reaction at the anode:  OH^– − e⁻  → OH × 4

OH– ion discharge in preference to SO₄^2–

                  4OH →  2H₂O + O₂ (oxygen molecule)