Chapter 3 Electrochemistry Class 12 Chemistry NCERT Solutions

Question 1:Arrange the following metals in the order in which they displace each other from the solution of their salts.
Al, Cu, Fe, Mg and Zn

Question 2:Given the standard electrode potentials,
K⁺/K = −2.93V, Ag⁺/Ag = 0.80V,
Hg²⁺/Hg = 0.79V
Mg²⁺/Mg = −2.37 V, Cr³⁺/Cr = − 0.74V Arrange these metals in their increasing order of reducing power.

Question 3:Depict the galvanic cell in which the reaction Zn(s) + 2Ag⁺(aq) → Zn²⁺(aq) + 2Ag(s)
takes place. Further show:
(i) Which of the electrode is negatively charged?
(ii) The carriers of the current in the cell.
(iii) Individual reaction at each electrode.

Question 4:Calculate the standard cell potentials of galvanic cells in which the following reactions
take place:
(i) 2Cr(s) + 3Cd²⁺(aq) → 2Cr³⁺(aq) + 3Cd
(ii) Fe²⁺(aq) + Ag⁺(aq) → Fe³⁺(aq) + Ag(s)
Calculate the =∆rG^θ and equilibrium constant of the reactions.

Question 5:Write the Nernst equation and emf of the following cells at 298 K:
(i) Mg(s) | Mg²⁺(0.001M) || Cu²⁺(0.0001 M) | Cu(s)
(ii) Fe(s) | Fe²⁺(0.001M) || H⁺(1M)|H₂(g)(1bar) | Pt(s)
(iii) Sn(s) | Sn²⁺(0.050 M) || H⁺(0.020 M) | H₂(g) (1 bar) | Pt(s)
(iv) Pt(s) | Br₂(l) | Br⁻(0.010 M) || H

Question 6:In the button cells widely used in watches and other devices the following reaction takesplace:
Zn(s) + Ag₂O(s) + H₂O(l) → Zn²⁺(aq) + 2Ag(s) + 2OH⁻(aq)
Determine and for the reaction.

Question 7:Define conductivity and molar conductivity for the solution of an electrolyte. Discuss their variation with concentration.

Question 8:The conductivity of 0.20 M solution of KCl at 298 K is 0.0248 Scm⁻¹. Calculate its molar conductivity.

Question 9:The resistance of a conductivity cell containing 0.001M KCl solution at 298 K is 500M. What is the cell constant if conductivity of 0.001M KCl solution at 298 K is 0.146 × 10⁻³S cm⁻¹.

Question 10:The conductivity of sodium chloride at 298 K has been determined at different concentrations and the results are given below:

Question 11: Conductivity of 0.00241 M acetic acid is 7.896 × 10⁻⁵ S cm⁻¹. Calculate its molar conductivity and if for acetic acid is 390.5 S cm² mol⁻¹, what is its dissociation constant?

Question 12:How much charge is required for the following reductions:
(i) 1 mol of Al³⁺ to Al.
(ii) 1 mol of Cu²⁺ to Cu.
(iii) 1 mol of MnO^4– to Mn²⁺.

Question 13:How much electricity in terms of Faraday is required to produce
(i) 20.0 g of Ca from molten CaCl₂.
(ii) 40.0 g of Al from molten Al₂O₃.

Question 14: How much electricity is required in coulomb for the oxidation of (i) 1 mol of H₂O to O₂. (ii) 1 mol of FeO to Fe₂O₃.

Question 15: A solution of Ni(NO₃)₂ is electrolysed between platinum electrodes using a current of 5 amperes for 20 minutes. What mass of Ni is deposited at the cathode?

Question 16:Three electrolytic cells A,B,C containing solutions of ZnSO₄, AgNO₃ and CuSO₄, respectively are connected in series. A steady current of 1.5 amperes was passed through them until 1.45 g of silver deposited at the cathode of cell B. How long did the current flow? What mass of copper and zinc were deposited?

Question 17: Using the standard electrode potentials given in Table 3.1, predict if the reaction between the following is feasible:
(i) Fe³⁺(aq) and I⁻(aq)
(ii) Ag⁺ (aq) and Cu(s)
(iii) Fe³⁺ (aq) and Br⁻(aq)
(iv) Ag(s) and Fe³⁺(aq)
(v) Br² (aq) and Fe²⁺ (aq).

Question 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.