Chemistry Class 12 NCERT Solutions: Chapter 3 Electrochemistry Part 10

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Q: 18. Predict the products of electrolysis in each of the following:

(i) An aqueous solution of with silver electrodes

(ii) An aqueous solution of with platinum electrodes

(iii) A dilute solution of with platinum electrodes

(iv) An aqueous solution of with platinum electrodes

Ans:

(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 anode is attacked by ions. Therefore, the silver electrode at the anode dissolves in the solution to form .

(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, or ions can be oxidized at the anode. But ions having a lower discharge potential and get preference and decompose to liberate .

(iii) At the cathode, the following reduction reaction occurs to produce gas.

At the anode, the following processes are possible.

For dilute sulphuric acid, reaction (i) is preferred to produce 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, gets oxidized at the anode to produce gas.