Questions for electrochemistry

SINGLE CORRECT ANSWER TYPE


Each of the following Question has 4 choices A, B, C & D, out of which ONLY ONE Choice is Correct.
3
1. The standard reduction potential values of Cr | Cr 2 and Cr3 | Cr half cells are -0.41 V and – 0.74V
respectively. The standard electrode potential of Cr2+ | Cr half-cell is :
(A) +1.81 V . (B) –1.81V (C) +0.9 V. (D) – 0.9 V.
2. An acidic solution  NO
3 or SO 4 2
 of Ag + +
salt containing 0.2 g of Ag is electrolysed until all the Ag is

deposited. The electrolysis is continued for 10 more minutes with the volume of solution kept at 500 ml and the
current at 2 ampere. Calculate volume of gases evolved at NTP during entire electrolysis.
(A) 138.88 ml, 79.74 ml (B) 159.48 ml, 79.74 ml
(C) 138.88 ml, 138.88 ml (D) 138.88 ml, 159.48 ml

3. Beryllium occurs naturally in the form of beryl. The metal is produced from its ore by electrolysis after the ore has
been converted to the oxide and then to the chloride. How many grams of Be(s) is deposited from a BeCl 2 solution
by a current of 5.0 A that flows for 1.0 h? (Atomic weight: Be = 9)
(A) 0.840 (B) 1.68 (C) 1.42 (D) 1.08

4. The element indium is to be obtained by electrolysis of a molten halide of the element. Passage of a current of
3.20 A for a period of 40.0 min results in formation of 3.05 g of In. What is the oxidation state of indium in the
halide melt? (Atomic weight : In = 114.8)
(A) 1 (B) 2 (C) 3 (D) 4

5. How may grams of Cr are deposited in the electrolysis of solution of Cr(NO3)3 in the same time that it takes to
deposit 0.54 g of Ag in a silver coulometer arranged in series with the Cr(NO 3)3 cell? (Atomic weight : Cr = 52.0;
Ag = 108)
(A) 0.0866 (B) 0.0288 (C) 0.173 g (D) 0.220

6. When a solution of AgNO3 (1 M) is electrolyzed using platinum anode and copper cathode. What are the reaction
occurring at two electrodes?
Given : E o  0.34 volt; E o  1.23 volt; E o   0.0 volt;
Cu 2 |Cu O 2 ,H  |H 2O H |H 2

Eo  0.8volt
Ag |Ag

(A) Cu  Cu 2  2e at anode; Ag+ + e   Ag at cathode
1
(B) H 2O  O2 + 2H+ + 2 e at anode; Cu2+ + 2 e  Cu at cathode
2
1
(C) H2O  O2 + 2H+ + 2e- at anode; Ag+ + e   Ag at cathode
2
(D) e  2H   N O + 
3  NO2 + H2O at anode; Ag + e 
 Ag at cathode
7. Based on the following information arrange four metals, A, B, C and D in the order of increasing ability to act as
reducing agents :
I. Only C react with 1 M HCl to give H2(g).
II. When A is added to solution of the other metal ions, metallic D is formed but not B or C.
(A) D < A < C < B (B) A < D < C < B (C) B < D < A < C (D) D<A<B<C

, 8. The Eo at 25º C for the following reaction at the indicated concentrations is 1.50 V. Calculate the ΔG in kJ at 25º
C for the given reaction: Cr s  3Ag aq,0.1M 
 3Ag s  Cr 3 aq,0.1M
(A) -140.94 (B) -295 (C) -212 (D) -422.83 kJ
9. Copper reduces NO3 into NO2 depending upon concentration of HNO3 in solution. Assuming [Cu2+] = 0.1 M,

and PNO2  103 bar, at which concentration of HNO3, thermodynamic tendency for reduction for of NO3 into



NO2 by copper is feasible? [Given : E o  0.34 volt., E o  0.79 volt]
Cu 2 |Cu NO
3 |NO 2

(A) 2.71106 M (B) 3105 M (C) 2 107 M (D) 2.71108 M

10. Molar conductivity of a solution of an electrolyte AB3 is 150 Scm2 mol-1. If it ionises as
AB3 
 A3+ + 3B-, its equivalent conductivity will be :
(A) 150 (in Scm2 eq-1) (B) 75 (in Scm2 eq-1)
(C) 50 (in Scm2 eq-1) (D) 80 (in Scm2 eq-1)

11. A galvanic cell is composed of two hydrogen electrodes, of which cathode is a standard hydrogen electrode. In
which of the following solutions, should the other electrode be immersed to get maximum e.m.f. ?
(A) 0.1 M HCl (B) 0.1 M H2SO4 (C) 0.1 M HCO2H (D) 0.01 M HCOOH

12. Pure water is saturated with pure solid AgCl, a silver electrode is placed in the solution and the potential is
measured against normal calomel electrode at 25ºC. The experiment is then repeated with a saturated solution of
AgI. If the difference in potential of the two cases is 0.177 V, what is the ratio of solubilities of AgCl and Agl at
the temperature of the experiment?
(A) 102 (B) 106 (C) 103 (D) 104

13. The EMF of the following cell is 0.265 V at 25ºC and 0.2595 V at 35ºC.
Pt  H2  / HCl  aq  || AgCl / Ag.
The heat of reaction taking place at 25ºC is
(A) – 90.8 kJ (B) – 80.8 kJ (C) –82.76 kJ (D) –41.38 kJ
14. The electrolytic conductivity of a saturated solution of AgCl in water at 25ºC is 1.26 106 Ω 1 cm–1 greater
than that for the water used. Calculate the solubility of AgCl in water if the molar ionic conductivities of Ag + and
Cl = 53.9 Ω1 cm–2 mol–1, and 72.1 Ω1cm2mol1 respectively.
(A) 0.95 10–5 g/L (B) 0.95 10–5 mol/L
(C) 0.95 10–2 mol/L (D) 0.95 10–2 g/L
15. Molar conductivities of ACl, BSO4, CPO4 and B3(PO4)2 are 200, 300, 500 and 700 S cm2 mol-1. Which of the
following solution has greater conducting ability?
(A) B3(PO4)2 (B) CPO4 (C) BSO4 (D) ACl

16. The molar conductivity of a weak acid (HA) at infinite dilution is 275 S cm2 mol-1 and that of 0.1 M solution of
HA is 5.5 S cm2 mol-1 at 25ºC. What is the dissociation constant of HA at the given temperature?
(A) 110 4 (B) 4.08104 (C) 4.08105 (D) 1105

17. Which of the following is(are) correct for a lead acid battery supplying electrical energy?
(A) PbSO4 is formed at one electrode only (B) Pb  H 2SO 4  PbSO 4  H 2
(C) Weight of electrolyte decreases (D) PbO2 accepts electrons as well as protons.