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.

Q.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.

Solution:

Remember

All ions are in aqueous state

(i)

Reaction in solution

AgNO₃               ↔     Ag ⁺    +        NO3^–

H₂O             ↔     H⁺       +        OH^–

Reaction at cathode

Ag⁺   +          e^–       →      Ag

Reaction at anode

Ag(s)  +        NO₃^– →      AgNO₃(aq)   +       e^–

Hence Ag will deposit at cathode and dissolve at anode

(ii)

Reaction in solution

AgNO₃               ↔     Ag ⁺    +        NO3^–

H₂O             ↔     H⁺       +        OH^–

Reaction at cathode

Ag⁺   +          e^–       →      Ag

Reaction at anode

Due to platinum electrode self of ionization of water will take place 

H₂O   →     2H⁺    +        1/2O2(g)   +  2e^–

Hence Ag will deposit at cathode and O2 gas will generate at anode

(iii)

Reaction in solution

H₂SO₄                          ↔     2H ⁺  +        SO₄^2–

H₂O             ↔     H⁺       +        OH^–

Reaction at cathode

H⁺      +          e^–       →      ½ H₂

Reaction at anode

Due to platinum electrode self of ionization of water will take place 

H₂O   →     2H⁺    +        1/2O₂(g)   +  2e^–

Hence H₂ gas will generate at cathode and O₂ gas will generate at anode

(iv)

Reaction in solution

CuCl₂(s)      ↔     Cu ²⁺            +        2Cl^–   

H₂O             ↔     H⁺       +        OH^–

Reaction at cathode

Cu²⁺    +        2e^–     →      Cu(S)

Reaction at anode

2Cl^–             →      Cl₂     +  2e^–

Hence Cu will deposit at cathode and Cl₂ gas will generate at anode