Page No 94: - Chapter 3 - Electrochemistry - Exercise Solutions - Ncert Solutions class 12 - Chemistry
Updated On 26-08-2025 By Lithanya
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Question 3.18:
Predict the products of electrolysis in each of the following:
(i) An aqueous solution of AgNO3 with silver electrodes.
(ii) An aqueous solution of AgNO3with platinum electrodes.
(iii) A dilute solution of H2SO4with platinum electrodes.
(iv) An aqueous solution of CuCl2 with platinum electrodes.
Answer:
(i) At cathode:
The following reduction reactions compete to take place at the cathode.
The reaction with a higher value of 
takes place at the cathode. Therefore, deposition of silver will take place at the cathode.
At anode:
The Ag anode is attacked by 
ions. Therefore, the silver electrode at the anode dissolves in the solution to form Ag+.
(ii) At cathode:
The following reduction reactions compete to take place at the cathode.
The reaction with a higher value of takes place at the cathode. Therefore, deposition of silver will take place at the cathode.
At anode:
Since Pt electrodes are inert, the anode is not attacked by ions. Therefore, OH− or ions can be oxidized at the anode. But OH− ions having a lower discharge potential and get preference and decompose to liberate O2.
(iii) At the cathode, the following reduction reaction occurs to produce H2 gas.
At the anode, the following processes are possible.
For dilute sulphuric acid, reaction (i) is preferred to produce O2 gas. But for concentrated sulphuric acid, reaction (ii) occurs.
(iv) At cathode:
The following reduction reactions compete to take place at the cathode.
The reaction with a higher value of takes place at the cathode. Therefore, deposition of copper will take place at the cathode.
At anode: The following oxidation reactions are possible at the anode.
At the anode, the reaction with a lower value of is preferred. But due to the over-potential of oxygen, Cl− gets oxidized at the anode to produce Cl2 gas.
