Question

Why are the products of electrolysis different for the electrolysis of aqueous solution of \( AgNO_{3} \) with silver electrodes and electrolysis of aqueous solution of \( AgNO_{3} \) with platinum electrodes?

Hint:

Using active electrodes is the basis for electroplating and electrolytic refining of metals.

Answer 1

Concept:

• The products of electrolysis depend on the nature of the electrodes.

• Inert electrodes (like Pt or Au) do not participate in the chemical reaction; they only provide a surface for electron transfer.

• Active electrodes (like Ag, Cu, or Ni) participate in the redox reactions themselves.
Step 1: Analyze with Platinum (Inert) Electrodes
At the Cathode: \( Ag^{+} \) ions are reduced to silver metal because silver has a higher reduction potential than water. \[ Ag^{+}(aq) + e^{-} \rightarrow Ag(s) \] At the Anode: Water is oxidized to Oxygen gas because the Pt electrode is inert and does not react. \[ 2H_{2}O(l) \rightarrow O_{2}(g) + 4H^{+}(aq) + 4e^{-} \]

Step 2: Analyze with Silver (Active) Electrodes
At the Cathode: \( Ag^{+} \) ions are still reduced to silver metal. \[ Ag^{+}(aq) + e^{-} \rightarrow Ag(s) \] At the Anode: The silver electrode itself is oxidized to \( Ag^{+} \) ions because the oxidation of Ag metal requires less energy than the oxidation of water. \[ Ag(s) \rightarrow Ag^{+}(aq) + e^{-} \]

Step 3: Compare the results
With Pt electrodes, Oxygen gas is produced at the anode. With Ag electrodes, the anode dissolves, and no gas is produced. The final answer is because silver electrodes are active and participate in the reaction, unlike inert platinum.