Predict the products of electrolysis in each of the following: (i) An aqueous solution of AgNO₃ with silver electrodes. (ii) An aqueous solution of AgNO₃ with platinum electrodes. (iii) A dilute solution of H₂SO₄ with platinum electrodes. (iv) An aqueous solution of CuCl₂ with platinum electrodes.
Silver electrodes are reactive electrodes. According to the context, reactive electrodes participate in electrode reactions. At the anode, silver metal oxidises to Ag⁺ ions (Ag → Ag⁺ + e⁻). At the cathode, Ag⁺ ions from solution are reduced to silver metal (Ag⁺ + e⁻ → Ag). The net result is transfer of silver from anode to cathode, and the AgNO₃ solution concentration remains constant.
Platinum electrodes are inert electrodes. The context states that inert electrodes do not participate in the chemical reaction and act only as source or sink for electrons. At the cathode, Ag⁺ ions are reduced to silver metal (Ag⁺ + e⁻ → Ag). At the anode, oxidation of species present in solution occurs. The AgNO₃ concentration decreases as silver deposits at cathode.
Platinum electrodes are inert electrodes. The dilute H₂SO₄ solution contains H⁺, SO₄²⁻ ions and water molecules. The context notes that for aqueous solutions, besides solute ions, H⁺, OH⁻, and H₂O are also present. At the cathode, H⁺ ions are reduced to H₂ gas. At the anode, water is oxidised to O₂ gas. The context mentions that overpotential affects which reactions occur.
Platinum electrodes are inert electrodes. The CuCl₂ solution contains Cu²⁺ and Cl⁻ ions. The context explicitly shows the cathode reaction: Cu²⁺(aq) + 2e⁻ → Cu(s). At the anode, Cl⁻ ions are oxidised to Cl₂ gas (2Cl⁻ → Cl₂ + 2e⁻). Copper metal deposits at cathode and chlorine gas evolves at anode.
Explanation
The context establishes fundamental principles for predicting electrolysis products: (1) Products depend on nature of material and type of electrodes used, (2) Inert electrodes (platinum, gold) do not participate in reactions while reactive electrodes do, (3) For aqueous solutions, H⁺, OH⁻, and H₂O are present besides solute ions, (4) Standard electrode potentials determine which reactions are feasible, and (5) Overpotential considerations affect reaction occurrence. The context provides the specific Cu²⁺ reduction reaction. For AgNO₃ with silver electrodes, the reactive nature of silver causes anode dissolution. For inert platinum electrodes, only species in solution participate in reactions.