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CHAPTER

ELECTROCHEMISTRY

1. On electrolysis of dilute sulphuric acid using platinum electrodes, the product obtained at the anode will be (a) hydrogen (b) oxygen (c) hydrogen sulphide (d) sulphur dioxide Ans: (b) 2. Which of the following is an insulator? (a) Graphite (b) Aluminium (c) Diamond (d) Silicon Ans: (c) 3.

(a) Na+ (b) Li+ (c) Ba2+ (d) Mg2+ Ans: (d) 4. The most durable metal plating on iron to protect against corrosion is (a) nickel plating (b) copper plating (c) tin plating (d) zinc plating Ans: (d) 5. On heating one end of a piece of a metal, the other end becomes hot because of (a) resistance of the metal (b) mobility of atoms in the metal (c) energised electrons moving to the other end (d) minor perturbation in the energy of atoms Ans: (c) 6. If 0.5 amp current is passed through acidified silver nitrate solution for 100 minutes. The mass of silver deposited on cathode, is (eq.wt.of silver nitrate = 108) (a) 2.3523 g

(b) 3.3575 g (c) 5.3578 g (d) 6.3575 g Ans: (b) 7.

(a) the temperature is constant (b) e.m.f depends on molarities of acids used (c) acids used in two compartments are different (d) pHof 0.1 MHCl and 0.1 MCH3COOH is not same Ans: (d) 8. On passing a current of 1.0 ampere for 16 min and 5 sec through one litre solution of CuCl2, all copper of the solution was deposited at cathode. The strength of CuCl2 solution was (Molar mass of Cu= 63.5; Faraday constant = 96,500 Cmol–1) (a) 0.01 N (b) 0.01 M (c) 0.02 M (d) 0.2 N Ans: (a) 9. Equivalent conductances of NaCl, HCl and CH3COONa at infinite dilution are 126.45, 426.16 and 91 ohm–1 cm2 respectively. The equivalent conductance of CH3COOH at infinite dilution would be (a) 101.38 ohm–1 cm2 (b) 253.62 ohm–1 cm2 (c) 390.71 ohm–1 cm2 (d) 678.90 ohm–1 cm2 Ans: (c)

10. If 0.01 Msolution of an electrolyte has a

resistance of 40 ohms in a cell having a cell constant of 0.4 cm–1, then its molar conductance in ohm–1 cm2 mol–1 is (a) 102 (b) 104 (c) 10 (d) 103 Ans: (d)

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11.

(a) 10-18

(b) 10-37

(c) 1018

(d) 1037

Ans: (d) 12.

(a)

(b)

(c)

(d) Ans: (b) 13.

(a) ln (C1) (b) ln (C2 /C1) (c) ln (C2) (d) ln (C1 + C2) Ans: (b) 14. Without losing its concentration ZnCl2 solution cannot be kept in contact with (a) Au (b) Al (c) Pb (d) Ag Ans: (b) 15.

(a) 0.5328 V (b) 0.3552 V (c) 0.1773 V (d) 0.7104 V Ans: (c) 16. The ionic conductance of Ba2+ and Cl– are respectively 127 and 76 ohm–1 cm2 at infinite dilution. The equivalent conductance (in ohm–1 cm2) of BaCl2 at infinite dilution will be: (a) 139.5 (b) 203 (c) 279 (d) 101.5 Ans: (a) 17.

(a) –0.38 V (b) +0.49 V (c) +0.38 V (d) –0.19 V Ans: (c) 18. Specific conductance of a 0.1 NKCl solution at 23ºC is 0.012 ohm–1 cm–1. Resistance of cell containing the solution at same temperature was found to be 55 ohm. The cell constant is (a) 0.918 cm–1 (b) 0.66 cm–1 (c) 1.142 cm–1 (d) 1.12 cm–1 Ans: (b) 19.

(a)

(b)

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(c)

(d) Ans: (b) 20. The most convenient method to protect the bottom of ship made of iron is (a) Coating it with red lead oxide (b) White tin plating (c) Connecting it with Mg block (d) Connecting it with Pb block Ans: (c) 21. In the silver plating of copper, K[Ag(CN) 2] is used instead of AgNO3. The reason is (a) Athin layer of Ag is formed on Cu (b) More voltage is required (c) Ag+ ions are completely removed from solution (d) Less availability of Ag+ ions, as Cu cannot displace Ag from [Ag(CN) 2] – ion Ans: (d) 22. Which reaction is not feasible?

(a)

(b)

(c)

(d) Ans: (b) 23. In electrolysis of NaCl when Pt electrode is taken then H2 is liberated at cathode while with Hg cathode it forms sodium amalgam. This is because (a) Hg is more inert than Pt (b) More voltage is required to reduce H+ at Hg than at Pt (c) Na is dissolved in Hg while it does not dissolve in Pt (d) Conc. of H+ ions is larger when Pt electrode is taken Ans: (b) 24.

(a)

(b)

(c)

(d) Ans: (b) 25.

(a) 8.56 V (b) 2.14 V (c) 4.28 V (d) 6.42 V Ans: (b) 26.

(a)

(b)

(c)

(d) Ans: (d) 27. 4.5 g of aluminium (at. mass 27 amu) is deposited at cathode from Al3+ solution by a certain quantity of electric charge. The volume of hydrogen produced at STP from H+ ions in solution by the same quantity of electric charge will be (a) 44.8 L (b) 22.4 L (c) 11.2 L (d) 5.6 L Ans: (d) 28.

(a) 1.653 V (b) 1.212 V (c) 0.111 V

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(d) 0.330 V Ans: (b) 29.

(a)

(b)

(c)

(d) Ans: (c) 30. The efficiency of a fuel cell is given by

(a)

(b)

(c)

(d) Ans: (b) 31.

(a) 2.0 × 1010 (b) 4.0 × 1010 (c) 4.0 × 1015 (d) 2.4 × 1010 Ans: (c) 32.

(a) [Fe(CN) 6] 4– (b) Fe2+ (c) Fe3+ (d) [Fe(CN) 6] 3– Ans: (c) 33. Kohlrausch’s law states that at: (a) finite dilution, each ion makes definite contribution to equivalent conductance of an

electrolyte, whatever be the nature of the other ion of the electrolyte. (b) infinite dilution each ion makes definite contribution to equivalent conductance of an electrolyte depending on the nature of the other ion of the electrolyte. (c) infinite dilution, each ion makes definite contribution to conductance of an electrolyte whatever be the nature of the other ion of the electrolyte. (d) infinite dilution, each ion makes definite contirubtion to equivalent conductance of an electrolyte, whatever be the nature of the other ion of the electrolyte. Ans: (d) 34.

(a) 1.968 V (b) 2.0968 V (c) 1.0968 V (d) 0.0968 V Ans: (c) 35.

(a) 0.90 V (b) 0.30 V (c) 0.38 V (d) 0.52 V Ans: (d) 36.

(a) 8.1 × 104 g (b) 2.4 × 105 g (c) 1.3 × 104 g (d) 9.0 × 103 g Ans: (a) 37.

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(a) 1.25 × 10–6 (b) 6.25 × 10–4 (c) 1.25 × 10–4 (d) 1.25 × 10–5 Ans: (d) 38.

(a) – 89.0 kJ (b) – 89.0 J (c) – 44.5 kJ (d) – 98.0 kJ Ans: (a) 39.

(a) increase in ionic mobility of ions (b) 100% ionisation of electrolyte at normal dilution (c) increase in both i.e. number of ions and ionic mobility of ions (d) increase in number of ions Ans: (a) 40.

(a)

(b)

(c)

(d) Ans: (c) 41.

(a) (ii) and (iv) (b) (iii) and (c) and (ii) (d) (iii) and (iv) Ans: (a) 42. Standard electrode potential of three metals X, Yand Zare – 1.2 V, + 0.5 Vand – 3.0 V, respectively. The reducing power of these metals will be: (a) Y> Z> X (b) X> Y> Z (c) Z> X> Y (d) X> Y> Z Ans: (c) 43.

(a) 0.500 V (b) 0.325 V (c) 0.650 V (d) 0.150 V Ans: (b) 44. Standard electrode potential for Sn4+/ Sn2+ couple is + 0.15 Vand that for the Cr3+/ Cr couple is – 0.74 V. These two couples in their standard state are connected to make a cell. The cell potential will be:

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(a) + 1.19 V (b) + 0.89 V (c) + 0.18 V (d) + 1.83 V Ans: (b) 45.

(a)

(b)

(c)

(d) Ans: (d) 46.

(a) I2 will be reduced to I– (b) There will be no redox reaction (c) I– will be oxidised to I2 (d) Fe2+ will be oxidised to Fe3+ Ans: (c) 47.

(a)

(b)

(c)

(d) Ans: (d) 48.

(a) 425.5 S cm2 mol–1 (b) 180.5 S cm2 mol–1

(c) 290.8 S cm2 mol–1 (d) 390.5 S cm2 mol–1 Ans: (d) 49. Ahydrogen gas electrode is made by dipping platinum wire in a solution of HCl of pH= 10 and by passing hydrogen gas around the platinum wire at one atm pressure. The oxidation potential of electrode would be? (a) 0.59 V (b) 0.118 V (c) 1.18 V (d) 0.059 V Ans: (a) 50.

(a) 20.800% (b) 4.008% (c) 40.800% (d) 2.080% Ans: (b) 51.

(a) 0.42 V (b) 0.84 V (c) 1.34 V (d) 1.10 V Ans: (d) 52. How many grams of cobalt metal will be deposited when a solution of cobalt (II) chloride is electrolyzed with a current of 10 amperes for 109 minutes (1 Faraday = 96,500 C; Atomic mass of Co = 59 u) (a) 0.66 (b) 4.0 (c) 20.0

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(d) 40.0 Ans: (c) 53.

(a) – 2.69 V and no (b) – 4.18 V and yes (c) + 0.33 V and yes (d) + 2.69 V and no Ans: (a) 1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

Chapterwise Previous year Qs

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11.

12.

13.

14.

15.

16.

17.

18.

19.

Chapterwise Previous year Qs

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20.

21.

22.

23.

24.

25.

26.

27.

28.

29.

30.

Chapterwise Previous year Qs

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31.

32.

33.

34.

35.

36.

37.

38.

39.

40.

41.

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42.

43.

44.

45.

46.

47.

48.

49.

50.

51.

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52.

53.