ELECTRO CHEMISTRY NCERT QUESTIONS
Exercises
3.1 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.
3.2 Given the standard electrode potentials,
Hg2+/Hg = 0.79V
Mg2+/Mg = –2.37 V, Cr3+/Cr = – 0.74V
Arrange these metals in their increasing order of reducing power.
3.3 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.
3.4 Calculate the standard cell potentials of galvanic cell 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 ΔrG_ and equilibrium constant of the reactions.
3.5 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+(0.030 M)| H2(g) (1 bar)|Pt(s).
3.6 In the button cells widely used in watches and other devices the following reaction
takes place:
Zn(s) + Ag2O(s) + H2O(l) → Zn2+(aq) + 2Ag(s) + 2OH–(aq)
Determine ΔrG_ and E_ for the reaction.
3.7 Define conductivity and molar conductivity for the solution of an electrolyte.
Discuss their variation with concentration.
3.8 The conductivity of 0.20 M solution of KCl at 298 K is 0.0248 S cm–1. Calculate
its molar conductivity.
3.9 The resistance of a conductivity cell containing 0.001M KCl solution at 298 K is
1500 Ω. What is the cell constant if conductivity of 0.001M KCl solution at 298
K is 0.146 × 10–3 S cm–1.
3.10 The conductivity of sodium chloride at 298 K has been determined at different
concentrations and the results are given below:
Concentration/M 0.001 0.010 0.020 0.050 0.100
102 × κ/S m–1 1.237 11.85 23.15 55.53 106.74
Calculate Λ
m for all concentrations and draw a plot between Λ
m and c½. Find the
value of 0
m Λ .
3.11 Conductivity of 0.00241 M acetic acid is 7.896 × 10–5 S cm–1. Calculate its molar
conductivity and if 0
m Λ for acetic acid is 390.5 S cm2 mol–1, what is its dissociation
constant?
3.12 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 MnO4
– to Mn2+.
3.13 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.
3.14 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.
3.15 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?
3.16 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?
3.17 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 Fe 3+ (aq)
(v) Br2 (aq) and Fe2+ (aq).
3.18 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.
No comments:
Post a Comment