Electrochemistry – Overview

Electrochemistry is the branch of chemistry that deals with the relationship between electrical energy and chemical reactions. It primarily focuses on redox (reduction–oxidation) reactions, where electrons are transferred between species. These reactions can either generate electricity, as in galvanic (voltaic) cells, or consume electricity to drive non-spontaneous reactions, as in electrolytic cells. Understanding electrochemistry is essential in fields such as energy storage, corrosion prevention, electroplating, and battery technology.

A key concept in electrochemistry is the electrochemical cell, which consists of two electrodes (anode and cathode) and an electrolyte. At the anode, oxidation occurs, while reduction takes place at the cathode. The flow of electrons through an external circuit generates electric current. The potential difference between electrodes is measured as cell potential (EMF), which determines whether a reaction is spontaneous. The Nernst equation is widely used to calculate cell potential under non-standard conditions, incorporating concentration, temperature, and number of electrons transferred.

Electrochemistry also involves important quantitative relationships governed by Faraday’s laws of electrolysis. These laws relate the amount of substance produced or consumed at electrodes to the quantity of electricity passed. Concepts such as conductivity, molar conductivity, and ionic mobility are crucial in understanding how electrolytes behave in solution. Applications of electrochemistry are vast, including batteries, fuel cells, electrolysis processes, corrosion control, and modern energy systems like supercapacitors.

100 Electrochemistry Numerical Problems with Answers

Section A: Basic Concepts (1–20)

1. Calculate charge passed by 2 A current in 5 s.
   Ans: 10 C
2. How many electrons in 1 C?
   Ans: $6.25 \times 10^{18}$
3. Charge for 2 mol electrons?
   Ans: 193000 C
4. Faraday constant value?
   Ans: 96500 C/mol
5. Current for 100 C in 10 s?
   Ans: 10 A
6. Time for 500 C at 5 A?
   Ans: 100 s
7. Charge for 0.5 mol electrons?
   Ans: 48250 C
8. Current if 200 C in 20 s?
   Ans: 10 A
9. Time for 96500 C at 1 A?
   Ans: 96500 s
10. Charge for 3 A in 2 min?
    Ans: 360 C
11. 1 F equals?
    Ans: 96500 C
12. Charge for 1 mol electrons?
    Ans: 96500 C
13. Current for 300 C in 30 s?
    Ans: 10 A
14. Time for 1000 C at 2 A?
    Ans: 500 s
15. Charge passed in 4 A for 25 s?
    Ans: 100 C
16. Current for 400 C in 40 s?
    Ans: 10 A
17. Charge for 1.5 mol electrons?
    Ans: 144750 C
18. Time for 200 C at 4 A?
    Ans: 50 s
19. Current for 600 C in 60 s?
    Ans: 10 A
20. Charge in 10 A for 10 s?
    Ans: 100 C

Section B: Faraday’s Laws (21–50)

21. Mass of Ag deposited by 96500 C?
    Ans: 108 g
22. Cu deposited by 193000 C (n=2)?
    Ans: 63.5 g
23. Al deposited by 289500 C (n=3)?
    Ans: 27 g
24. Zn deposited by 193000 C?
    Ans: 65.4 g
25. Charge for 1 g Ag?
    Ans: 893 C
26. Mass Cu by 96500 C?
    Ans: 31.75 g
27. Ag deposited by 48250 C?
    Ans: 54 g
28. Mass Fe by 193000 C (n=2)?
    Ans: 55.8 g
29. Charge for 2 g Cu?
    Ans: 6079 C
30. Mass Zn by 96500 C?
    Ans: 32.7 g
31. Al by 96500 C?
    Ans: 9 g
32. Charge for 10 g Ag?
    Ans: 8935 C
33. Mass Cu by 48250 C?
    Ans: 15.9 g
34. Zn by 48250 C?
    Ans: 16.35 g
35. Fe by 96500 C?
    Ans: 27.9 g
36. Charge for 5 g Al?
    Ans: 5350 C
37. Cu by 289500 C?
    Ans: 95.25 g
38. Ag by 193000 C?
    Ans: 216 g
39. Zn by 289500 C?
    Ans: 98.1 g
40. Fe by 289500 C?
    Ans: 83.7 g
41. Charge for 1 mol Cu?
    Ans: 193000 C
42. Ag by 1 F?
    Ans: 108 g
43. Zn by 1 F?
    Ans: 32.7 g
44. Cu by 2 F?
    Ans: 63.5 g
45. Fe by 2 F?
    Ans: 55.8 g
46. Al by 3 F?
    Ans: 27 g
47. Zn by 2 F?
    Ans: 65.4 g
48. Ag by 0.5 F?
    Ans: 54 g
49. Cu by 0.5 F?
    Ans: 15.9 g
50. Fe by 0.5 F?
    Ans: 13.95 g

Section C: EMF and Nernst Equation (51–80)

51. EMF if E° = 1.1 V?
    Ans: 1.1 V
52. EMF for Daniell cell?
    Ans: 1.10 V
53. If [Zn²⁺]=1M, [Cu²⁺]=1M?
    Ans: 1.10 V
54. EMF if [Zn²⁺]=0.1, [Cu²⁺]=1?
    Ans: 1.13 V
55. EMF if [Zn²⁺]=1, [Cu²⁺]=0.1?
    Ans: 1.07 V
56. EMF at equilibrium?
    Ans: 0 V
57. n value for Zn-Cu cell?
    Ans: 2
58. Log 10 value?
    Ans: 1
59. EMF if Q=1?
    Ans: E°
60. EMF decreases with?
    Ans: Increase in Q
61. EMF increases with?
    Ans: Decrease in Q
62. EMF at high temp?
    Ans: Slight change
63. E° cell formula?
    Ans: Cathode − Anode
64. Sign of spontaneous EMF?
    Ans: Positive
65. EMF if Q>1?
    Ans: Decreases
66. EMF if Q<1?
    Ans: Increases
67. Standard condition temp?
    Ans: 298 K
68. Nernst factor at 298K?
    Ans: 0.0591
69. Unit of EMF?
    Ans: Volt
70. Relation EMF & ΔG?
    Ans: Negative
71. ΔG sign for spontaneous?
    Ans: Negative
72. EMF at equilibrium?
    Ans: Zero
73. n for Ag⁺ → Ag?
    Ans: 1
74. n for Al³⁺ → Al?
    Ans: 3
75. EMF for non-spontaneous?
    Ans: Negative
76. Effect of concentration?
    Ans: Changes EMF
77. Standard EMF symbol?
    Ans: E°
78. Unit of ΔG?
    Ans: J
79. Relation ΔG =?
    Ans: −nFE
80. EMF for electrolytic cell?
    Ans: Negative

Section D: Conductance (81–100)

81. Unit of conductance?
    Ans: Siemens
82. Unit of conductivity?
    Ans: S cm⁻¹
83. Molar conductivity unit?
    Ans: S cm² mol⁻¹
84. Conductance inverse of?
    Ans: Resistance
85. Resistance unit?
    Ans: Ohm
86. Conductivity increases with dilution?
    Ans: Yes
87. Molar conductivity increases?
    Ans: Yes
88. Strong electrolyte dissociation?
    Ans: Complete
89. Weak electrolyte dissociation?
    Ans: Partial
90. Kohlrausch law applies to?
    Ans: Weak electrolytes
91. Conductivity depends on?
    Ans: Ions
92. Temperature effect?
    Ans: Increases conductivity
93. Cell constant unit?
    Ans: cm⁻¹
94. Resistance relation?
    Ans: R = ρl/A
95. Conductivity symbol?
    Ans: κ
96. Molar conductivity symbol?
    Ans: Λm
97. Limiting conductivity?
    Ans: Infinite dilution
98. Ionic mobility increases?
    Ans: With dilution
99. Conductivity of pure water?
    Ans: Very low
100. Electrolytes conduct by?
     Ans: Ions