1.

Predict the products of electrolysis in each of the following:(i) An aqueous solution of AgNO3 with silver electrodes. (ii) An aqueous solution of AgNO3 with platinum electrodes. (iii) A dilute solution of H2SO4 with 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 

Ag+(aq) + e- → Ag(s); Eθ = 0.80 V 

H+ (aq) + e- → H2 (g); Eθ = 0.00V 

The reaction with a higher value of Eθ takes place of the cathode. 

Therefore, deposition of silver will take place at the cathode. 

At anode: The Ag anode is attacked by NO3- ions. 

Therefore, the silver electrode at the anode dissolves in the solution to form Ag+

(ii) At cathode: Same as above At anode: Anode is not attackable and hence OHions have lower discharge potential than NO3- ions and OH- ions react to give O2 

OH- → OH + e- 

4OH → 2H2O + O2 (g)

(iii) H2SO4 → 2H+ + SO2-4 

HO2 ⇌ H+ + OH

At cathode: 

2H+ + 2e- → H2 

At anode: 4OH- → 2H2O + O2 + 4e- 

i. e., H2 will be liberated at cathode and O2 at anode. 

(iv) CuCl2 → Cu2+ + 2Cl- 

At Cathode: Cu2+ ions will be reduced in preference to H+ ions 

Cu2+ + 2e → Cu At anode: Cl- ions will be oxidised in preference to OH- ions. 

2Cl- → Cl2 + 2e- 

i.e., Cu will be deposited on the cathode and Cl2 will be liberated at the anode.



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