{Please answer the Question no.3.18 from Chapter 3, NCERT Chemistry. It is not answered in Textbook Solutions Completely, part (iii) and (iv) are remaining. Also explain the (ii) part.}

Asked by Suyog Gadhave | 11th Feb, 2014, 12:35: PM

Expert Answer:

(i) At cathode:

            The following reduction reactions compete to take place at the cathode.

               

           

 The reaction with a higher value of E0 takes place at the cathode. Therefore, deposition of silver will take place at the cathode.

            At anode:

 The Ag anode is attacked by  NO3ions. 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 E0 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 NO3-   ions. Therefore, OH or   NO3- 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 E0 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 E0 is preferred. But due to the overpotential of oxygen, Cl gets oxidized at the anode to produce Cl2 gas.

 

Answered by  | 12th Feb, 2014, 02:32: PM

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