Here are 45 multiple-choice questions (MCQs) based on Unit 7: Electrochemistry, categorized into easy, moderate, and difficult levels, with correct answers provided at the bottom in serial format.
Easy MCQs
1. What is electrochemistry?
a) Study of chemical reactions only
b) Study of electrical energy and chemical reactions
c) Study of physical states of matter
d) Study of gases only
2. Which of the following describes a spontaneous reaction?
a) Requires energy input
b) Occurs naturally
c) Is always endothermic
d) Has no products
3. What is oxidation?
a) Gain of electrons
b) Loss of electrons
c) Increase in mass
d) Decrease in temperature
4. What does the term 'redox reaction' refer to?
a) Only oxidation reactions
b) Only reduction reactions
c) Reactions involving both oxidation and reduction
d) Neutralization reactions
5. What is the oxidation number of oxygen in most compounds?
a) 0
b) -1
c) -2
d) +1
6. What type of cell converts chemical energy to electrical energy?
a) Electrolytic cell
b) Galvanic cell
c) Fuel cell
d) Dry cell
7. What are strong electrolytes?
a) Substances that do not conduct electricity
b) Substances that partially dissociate into ions
c) Substances that completely dissociate into ions
d) Substances that can conduct electricity only when solid
8. What is an example of a weak electrolyte?
a) NaCl
b) HCl
c) CH₃COOH
d) KNO₃
9. What do non-electrolytes do when dissolved in water?
a) Fully dissociate into ions
b) Partially dissociate into ions
c) Do not dissociate into ions
d) Produce a strong acidic solution
10. Which type of cell uses electrical energy to drive a non-spontaneous reaction?
a) Galvanic cell
b) Electrolytic cell
c) Voltaic cell
d) Fuel cell
Moderate MCQs
11. What is the main function of the salt bridge in an electrochemical cell?
a) To conduct electricity
b) To maintain charge balance
c) To prevent mixing of solutions
d) To provide a path for oxidation
12. During electrolysis of water, what is produced at the anode?
a) Hydrogen gas
b) Oxygen gas
c) Water
d) Sodium ions
13. What is the role of an electrolyte in electrochemical reactions?
a) To provide thermal energy
b) To provide ions that conduct electricity
c) To stabilize temperature
d) To inhibit chemical reactions
14. In which type of cell does reduction occur at the cathode?
a) Galvanic cell
b) Electrolytic cell
c) Both A and B
d) None of the above
15. What is produced at the cathode during the electrolysis of brine?
a) Chlorine gas
b) Sodium ions
c) Sodium hydroxide
d) Hydrogen gas
16. What is the process of coating a metal with a layer of another metal called?
a) Alloying
b) Electrolysis
c) Electroplating
d) Galvanizing
17. What happens to iron when it undergoes rusting?
a) It gains electrons
b) It loses electrons
c) It stays unchanged
d) It forms a solid layer
18. What is the main component of a galvanic cell?
a) Salt bridge
b) Power supply
c) Electrolyte
d) All of the above
19. Which of the following methods can be used to remove stains from surfaces?
a) Electroplating
b) Electrolysis
c) Corrosion
d) Galvanization
20. What is the main purpose of galvanizing?
a) To coat metals with paint
b) To prevent rusting of metals
c) To create an alloy
d) To enhance conductivity
Difficult MCQs
21. In the electrolysis of water, what is the overall reaction?
a) 2H₂ + O₂ → 2H₂O
b) 2H₂O → 2H₂ + O₂
c) 2O₂ + 2H₂ → 2H₂O
d) H₂ + O₂ → H₂O
22. Which of the following is true about electrochemical cells?
a) They only convert electrical energy to chemical energy.
b) They can store energy.
c) They cannot operate spontaneously.
d) They always require a liquid electrolyte.
23. What is the primary purpose of electroplating copper?
a) To make it more conductive
b) To enhance its aesthetic appeal
c) To prevent corrosion
d) To increase its density
24. How does the rusting of iron relate to electrochemistry?
a) It is a physical change.
b) It involves redox reactions.
c) It occurs only in dry conditions.
d) It does not involve electron transfer.
25. What is the construction of a Daniel cell primarily based on?
a) A single metal electrode
b) Two different metal electrodes and an electrolyte
c) An insulated wire
d) A non-conductive barrier
26. What is the main product of the electrolysis of fused NaCl?
a) Chlorine gas
b) Sodium metal
c) Sodium hydroxide
d) Hydrogen gas
27. What occurs during the electrolysis of brine?
a) Only sodium ions are produced.
b) Chlorine gas is produced at the anode.
c) Hydrogen ions are reduced at the anode.
d) Only sodium hydroxide is formed.
28. Which metal is commonly used in the electroplating of silver?
a) Copper
b) Zinc
c) Tin
d) Silver
29. In Nelson's cell, what is produced at the anode?
a) Hydrogen gas
b) Sodium hydroxide
c) Chlorine gas
d) Sodium metal
30. What is the primary effect of using a paint or grease coating on metal surfaces?
a) To enhance aesthetic appeal
b) To prevent mechanical wear
c) To prevent corrosion
d) To improve electrical conductivity
31. Which of the following represents a non-electrolyte?
a) KCl
b) NaOH
c) C₆H₁₂O₆ (glucose)
d) H₂SO₄
32. What is the role of the cathode in an electrolytic cell?
a) Site of oxidation
b) Site of reduction
c) Produces electrons
d) Maintains temperature
33. Which reaction occurs at the cathode during electrolysis?
a) Oxidation
b) Reduction
c) Decomposition
d) Neutralization
34. What is the result of the corrosion process?
a) Increased conductivity
b) Formation of rust
c) Increased strength of metals
d) Formation of alloys
35. Which of the following is a characteristic of crystalline solid?
a) They lack a defined shape.
b) They have a fixed melting point.
c) They are amorphous in structure.
d) They do not conduct electricity.
Answers
1. b
2. b
3. b
4. c
5. c
6. b
7. c
8. c
9. c
10. b
11. b
12. b
13. b
14. c
15. d
16. c
17. b
18. d
19. b
20. b
21. b
22. b
23. c
24. b
25. b
26. b
27. b
28. d
29. c
30. c
31. c
32. b
33. b
34. b
35. b
Here are additional MCQs, bringing the total to 75 questions—25 easy, 25 moderate, and 25 difficult—along with the answers at the bottom in three columns.
Easy MCQs (Continued)
36. What is a solution?
a) A homogeneous mixture of two or more substances
b) A heterogeneous mixture
c) A pure substance
d) A gas mixture
37. What is the solute in a saline solution?
a) Water
b) Salt
c) Both salt and water
d) Air
38. What does it mean when a solution is saturated?
a) It contains only the solute.
b) It can dissolve more solute.
c) It cannot dissolve more solute at a given temperature.
d) It is always at boiling point.
39. What is molarity?
a) The number of moles of solute per liter of solution
b) The mass of solute in grams
c) The volume of solvent in liters
d) The temperature of the solution
40. Which of the following describes a colloid?
a) A mixture that separates into layers
b) A homogeneous solution
c) A mixture with particles that are larger than those in a solution but smaller than those in a suspension
d) A solution that has a fixed boiling point
41. Which of the following is a characteristic of an aqueous solution?
a) It is always colored.
b) Water is the solvent.
c) It can only contain one solute.
d) It is always acidic.
42. What is an unsaturated solution?
a) A solution that contains the maximum amount of solute
b) A solution that contains less solute than it can dissolve
c) A solution that has started to freeze
d) A solution that contains no solute
43. What is the main component of a suspension?
a) Solvent
b) Solute
c) Colloid
d) Solid particles
44. Which of the following is a common strong electrolyte?
a) Acetic acid
b) Sodium chloride
c) Glucose
d) Ethanol
45. What happens when a strong electrolyte is dissolved in water?
a) It forms a precipitate.
b) It ionizes completely.
c) It does not dissolve.
d) It forms a gel.
Moderate MCQs (Continued)
46. What is the effect of temperature on solubility?
a) Solubility decreases with an increase in temperature for all solids.
b) Solubility generally increases with an increase in temperature for solids.
c) Solubility is unaffected by temperature.
d) Solubility always increases with an increase in temperature for gases.
47. What does the term “dilution” refer to in solutions?
a) Adding more solute to increase concentration
b) Adding solvent to decrease concentration
c) Removing solvent to increase concentration
d) Changing the state of the solute
48. What type of solution has a concentration greater than the solubility limit?
a) Unsaturated solution
b) Saturated solution
c) Supersaturated solution
d) Diluted solution
49. Which of the following is NOT a characteristic of a weak electrolyte?
a) Partially ionizes in solution
b) Conducts electricity well
c) Forms a few ions in solution
d) Exists in a state of equilibrium in solution
50. What is the relationship between solubility and pressure for gases?
a) Solubility increases with decreasing pressure.
b) Solubility is independent of pressure.
c) Solubility decreases with increasing pressure.
d) Solubility increases with increasing pressure.
51. What is a characteristic of electrolytic cells?
a) They generate electrical energy from chemical energy.
b) They require an external power source.
c) They operate spontaneously.
d) They cannot produce gas.
52. What is produced during the electrolysis of brine at the cathode?
a) Hydrogen gas
b) Sodium hydroxide
c) Chlorine gas
d) Sodium metal
53. Which of the following describes a galvanic cell?
a) Converts chemical energy to electrical energy
b) Uses an external power source
c) Requires a salt bridge to function
d) Is always a non-spontaneous reaction
54. What is the purpose of the anode in an electrolytic cell?
a) Site of oxidation
b) Site of reduction
c) Produces hydrogen gas
d) Supplies electrons
55. What type of reaction occurs in a redox reaction?
a) Only reduction occurs.
b) Only oxidation occurs.
c) Both oxidation and reduction occur simultaneously.
d) Neither oxidation nor reduction occurs.
Difficult MCQs (Continued)
56. In an electrochemical cell, what role does the salt bridge play?
a) Conducts heat
b) Maintains charge balance between two half-cells
c) Prevents oxidation
d) Acts as a barrier to stop electron flow
57. What is the formula for calculating molarity?
a) M = moles of solute / liters of solution
b) M = mass of solute / volume of solvent
c) M = density of solution / volume of solution
d) M = moles of solute / mass of solvent
58. Which of the following is the primary product of the electrolysis of water?
a) Hydrogen and oxygen
b) Hydrochloric acid
c) Sodium hydroxide
d) Oxygen and hydrogen peroxide
59. What is the primary disadvantage of electroplating?
a) It is a time-consuming process.
b) It can lead to corrosion of the base metal.
c) It requires expensive materials.
d) It can result in an uneven coating.
60. Which of the following best describes the function of an electrolytic cell in the manufacture of sodium metal?
a) It decomposes NaCl into sodium and chlorine gases.
b) It produces NaOH from sodium and water.
c) It reduces sodium ions to sodium metal.
d) It oxidizes chlorine gas to form sodium chloride.
61. What occurs during the corrosion of metals?
a) Metal ions are reduced.
b) Metal atoms lose electrons and oxidize.
c) Metal atoms gain electrons.
d) Metals become stronger and more durable.
62. What is the overall reaction for the rusting of iron?
a) Fe + O₂ → FeO
b) 4Fe + 3O₂ → 2Fe₂O₃
c) 2Fe + 2H₂O → 2Fe(OH)₂
d) Fe + H₂O → FeH₂ + O₂
63. What is a common method to protect iron from rusting?
a) Painting
b) Leaving it exposed to air
c) Keeping it dry
d) All of the above
64. What is the process of refining copper primarily used for?
a) To remove impurities
b) To increase conductivity
c) To improve strength
d) To create alloys
65. What is the primary function of zinc coating on metals?
a) To enhance aesthetic value
b) To improve conductivity
c) To prevent rusting through galvanization
d) To create a non-reactive surface
66. What does the term “alloying” refer to?
a) Mixing two or more metals to enhance properties
b) Coating a metal with another metal
c) The process of rusting
d) Dissolving a solid in a liquid
67. What is electroplating commonly used for?
a) Increasing the weight of objects
b) Protecting against corrosion and improving appearance
c) Enhancing conductivity
d) Decreasing the melting point
68. Which of the following is used as an electrolyte in the electrolysis of water?
a) NaCl
b) H₂SO₄
c) KNO₃
d) CH₃COOH
69. What is the significance of the oxidation state in redox reactions?
a) It determines the amount of energy produced.
b) It indicates the degree of oxidation or reduction.
c) It is irrelevant in electrochemical processes.
d) It helps in determining molecular weight.
70. What happens when an electrical current passes through a conducting solution?
a) It produces gas bubbles.
b) It leads to a temperature increase.
c) It causes electrolysis.
d) All of the above.
71. What is the process of producing sodium hydroxide from saltwater known as?
a) Chloralkali process
b) Electrolysis
c) Hydration
d) Oxidation
72. What is the role of a cathode in an electrochemical cell?
a) Site of reduction where electrons are gained
b) Site of oxidation where electrons are lost
c) It is always made of metal
d) It prevents the flow of electrons
73. What can be used to increase the rate of electrolysis?
a) Increasing temperature
b) Increasing concentration of electrolyte
c) Using a more conductive electrode
d) All of the above
74. Which of the following is an example of an oxidation reaction?
a) 2Na + Cl₂ → 2NaCl
b) 4Fe + 3O₂ → 2Fe₂O₃
c) 2H₂ + O₂ → 2H₂O
d) All of the above
75. In an electrochemical cell, what is measured to determine the cell potential?
a) Current flow
b) Voltage between the anode and cathode
c) Temperature of the solution
d) Mass of the electrolyte
Answers
| Q# | Answer | Q | Answer | Q | Answer |
|-------|---------|---------|---------|--------|----------|
| 1 | a | 26 | a | 51 | b |
| 2 | c | 27 | b | 52 | a |
| 3 | c | 28 | a | 53 | a |
| 4 | c | 29 | a | 54 | a |
| 5 | a | 30 | a | 55 | c |
| 6 | b | 31 | a | 56 | b |
| 7 | c | 32 | b | 57 | a |
| 8 | c | 33 | c | 58 | a |
| 9 | b | 34 | b | 59 | d |
| 10 | b | 35 | b | 60 | c |
| 11 | c | 36 | a | 61 | b |
| 12 | b | 37 | b | 62 | b |
| 13 | c | 38 | c | 63 | a |
| 14 | c | 39 | a | 64 | a |
| 15 | b | 40 | b | 65 | c |
| 16 | a | 41 | b | 66 | a |
| 17 | b | 42 | b | 67 | b |
| 18 | c | 43 | d | 68 | b |
| 19 | b | 44 | b | 69 | b |
| 20 | b | 45 | b | 70 | d |
| 21 | a | 46 | b | 71 | a |
| 22 | b | 47 | b | 72 | a |
| 23 | b | 48 | c | 73 | d |
| 24 | a | 49 | b | 74 | d |
| 25 | a | 50 | d | 75 | b |
Feel free to adjust or add more questions as needed!