Why are products of electrolysis of $AgNO_3$ different with silver electrodes and platinum electrodes?
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Solution and Explanation
The nature of the electrode (active vs. inert) determines whether the electrode itself participates in the redox reaction.
Step 2: Analysis (Platinum electrodes)
Platinum is an inert electrode; it does not dissolve. At the cathode: $Ag^+$ ions are reduced and silver metal deposits. At the anode: water is oxidized releasing $O_2$ gas (since $NO_3^-$ is hard to oxidize). The solution's $AgNO_3$ concentration decreases.
Step 3: Analysis (Silver electrodes)
Silver is an active electrode; it participates in the reaction. At the cathode: $Ag^+$ ions reduce to Ag (silver deposits). At the anode: the silver metal of the anode itself oxidizes ($Ag \rightarrow Ag^+ + e^-$), replenishing the $Ag^+$ ions in solution. Net result: silver transfers from anode to cathode. Solution concentration remains constant.
Final Answer: With Pt (inert): Ag deposits at cathode, $O_2$ released at anode. With Ag (active): Ag deposits at cathode, Ag anode dissolves. The active silver electrode replenishes $Ag^+$ ions.
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