1. What is an electrochemical cell?
- a) A device that converts chemical energy into electrical energy
- b) A device that converts electrical energy into mechanical energy
- c) A device that converts mechanical energy into chemical energy
- d) A device that converts heat energy into chemical energy
Answer: a) A device that converts chemical energy into electrical energy
Explanation: Electrochemical cells use chemical reactions to generate electricity.
2. In an electrochemical cell, the anode is where:
- a) Oxidation takes place
- b) Reduction takes place
- c) Electrons are consumed
- d) Protons are produced
Answer: a) Oxidation takes place
Explanation: In an electrochemical cell, oxidation occurs at the anode.
3. Which of the following is NOT a type of electrochemical cell?
- a) Galvanic (Voltaic) cell
- b) Electrolytic cell
- c) Fuel cell
- d) Nuclear cell
Answer: d) Nuclear cell
Explanation: Galvanic, electrolytic, and fuel cells are all types of electrochemical cells, while nuclear cells are unrelated to electrochemistry.
4. The electrode where reduction occurs is called:
- a) Cathode
- b) Anode
- c) Salt bridge
- d) Electrolyte
Answer: a) Cathode
Explanation: Reduction takes place at the cathode in both galvanic and electrolytic cells.
5. In a galvanic cell, the direction of electron flow is:
- a) From anode to cathode
- b) From cathode to anode
- c) In both directions
- d) None of the above
Answer: a) From anode to cathode
Explanation: Electrons always flow from the anode (where oxidation occurs) to the cathode (where reduction occurs) in a galvanic cell.
6. In an electrolytic cell, the anode is:
- a) Positive
- b) Negative
- c) Neutral
- d) Depends on the electrolyte
Answer: a) Positive
Explanation: In electrolytic cells, the anode is positive because an external power source forces the oxidation reaction at this electrode.
7. Which of the following components is necessary in a galvanic cell to complete the circuit?
- a) Salt bridge
- b) Diode
- c) Resistor
- d) Capacitor
Answer: a) Salt bridge
Explanation: The salt bridge allows the flow of ions to maintain electrical neutrality in the cell, ensuring continuous electron flow through the external circuit.
8. The function of a salt bridge in an electrochemical cell is to:
- a) Transfer electrons
- b) Provide ionic contact between the two half-cells
- c) Maintain the pH of the solution
- d) Provide a solid medium for the reaction
Answer: b) Provide ionic contact between the two half-cells
Explanation: A salt bridge helps to maintain charge balance by allowing ions to flow between the two solutions in a galvanic cell.
9. In a galvanic cell, the cell potential is positive when:
- a) The cell is operating spontaneously
- b) The cell is in equilibrium
- c) The external power source is switched off
- d) The concentrations of electrolytes are equal
Answer: a) The cell is operating spontaneously
Explanation: A positive cell potential indicates that the galvanic cell is spontaneous, meaning the reaction is favorable and electricity is generated.
10. Which of the following best describes a standard hydrogen electrode (SHE)?
- a) It is used as a reference electrode with a potential of 1V
- b) It has a standard electrode potential of 0V
- c) It acts as the cathode in all electrochemical cells
- d) It is composed of a copper wire immersed in hydrogen gas
Answer: b) It has a standard electrode potential of 0V
Explanation: The standard hydrogen electrode (SHE) is defined as having an electrode potential of 0V, and is used as a reference point to measure other electrode potentials.
11. The potential of a galvanic cell depends on:
- a) The nature of the electrodes and the concentration of electrolytes
- b) The temperature only
- c) The volume of the electrolyte
- d) The surface area of the salt bridge
Answer: a) The nature of the electrodes and the concentration of electrolytes
Explanation: The cell potential is affected by the type of electrodes used, the concentration of the electrolyte solutions, and temperature, according to the Nernst equation.
12. Which of the following reactions occurs at the cathode in an electrochemical cell?
- a) Reduction
- b) Oxidation
- c) Electrolysis
- d) Ionization
Answer: a) Reduction
Explanation: In both galvanic and electrolytic cells, reduction (gain of electrons) occurs at the cathode.
13. If the standard reduction potential of a half-cell is negative, it means that:
- a) The substance is easily reduced
- b) The substance is easily oxidized
- c) The cell potential is zero
- d) The reaction will never occur
Answer: b) The substance is easily oxidized
Explanation: A negative reduction potential indicates that the substance has a lower tendency to gain electrons and will more readily undergo oxidation.
14. The electrolyte in a dry cell is usually:
- a) Zinc sulfate
- b) Ammonium chloride
- c) Sodium hydroxide
- d) Copper sulfate
Answer: b) Ammonium chloride
Explanation: In a common dry cell (like a zinc-carbon battery), the electrolyte is usually a paste of ammonium chloride.
15. In a lead-acid battery, the anode is made of:
- a) Lead dioxide (PbO₂)
- b) Lead (Pb)
- c) Zinc (Zn)
- d) Nickel (Ni)
Answer: b) Lead (Pb)
Explanation: In a lead-acid battery, the anode is made of lead (Pb), while the cathode is made of lead dioxide (PbO₂).
16. In a Daniell cell, the half-cell reactions involve:
- a) Copper and zinc electrodes
- b) Iron and zinc electrodes
- c) Silver and copper electrodes
- d) Nickel and zinc electrodes
Answer: a) Copper and zinc electrodes
Explanation: The Daniell cell consists of a zinc electrode in a solution of zinc sulfate and a copper electrode in a solution of copper sulfate.
17. Which of the following statements is true for a galvanic cell?
- a) The anode is positive
- b) The cathode is negative
- c) The anode is negative
- d) Both electrodes are neutral
Answer: c) The anode is negative
Explanation: In a galvanic cell, the anode is negative because oxidation occurs there, releasing electrons into the external circuit.
18. The purpose of the external circuit in an electrochemical cell is to:
- a) Allow ions to flow between the electrodes
- b) Transfer electrons from the anode to the cathode
- c) Maintain pH balance
- d) Dissipate heat generated by the reaction
Answer: b) Transfer electrons from the anode to the cathode
Explanation: The external circuit allows the flow of electrons from the anode to the cathode, completing the electrical circuit.
19. The electrode potential of a half-cell depends on:
- a) The nature of the electrode material only
- b) The concentration of the electrolyte only
- c) Both the nature of the electrode and the concentration of the electrolyte
- d) The distance between the electrodes
Answer: c) Both the nature of the electrode and the concentration of the electrolyte
Explanation: The electrode potential is influenced by the type of electrode material and the concentration of the ions in the electrolyte, as per the Nernst equation.
20. In a standard electrochemical cell, the standard conditions are:
- a) 1 M concentration, 25°C, 1 atm pressure
- b) 0.1 M concentration, 25°C, 1 atm pressure
- c) 1 M concentration, 100°C, 1 atm pressure
- d) 0.5 M concentration, 0°C, 1 atm pressure
Answer: a) 1 M concentration, 25°C, 1 atm pressure
Explanation: Standard electrode potentials are measured under standard conditions, which are 1 M concentration of ions, 25°C (298 K) temperature, and 1 atm pressure.
21. Which of the following metals has the highest tendency to be oxidized?
- a) Copper
- b) Zinc
- c) Gold
- d) Silver
Answer: b) Zinc
Explanation: Zinc has a more negative standard electrode potential than copper, gold, or silver, which means it is more easily oxidized.
22. Which of the following statements is true for an electrolytic cell?
- a) The anode is positive and oxidation occurs there
- b) The cathode is positive and reduction occurs there
- c) The anode is negative and oxidation occurs there
- d) The cathode is positive and oxidation occurs there
Answer: a) The anode is positive and oxidation occurs there
Explanation: In an electrolytic cell, the anode is positive because the external source forces oxidation to occur at that electrode.
23. The cell notation for a galvanic cell is written as:
- a) Anode | electrolyte || cathode | electrolyte
- b) Cathode | electrolyte || anode | electrolyte
- c) Electrolyte | cathode || electrolyte | anode
- d) None of the above
Answer: a) Anode | electrolyte || cathode | electrolyte
Explanation: In cell notation, the anode and its electrolyte are written on the left, and the cathode and its electrolyte are written on the right, with a double vertical line (||) representing the salt bridge.
24. Electrolysis of molten NaCl produces:
- a) Sodium metal and chlorine gas
- b) Sodium metal and oxygen gas
- c) Sodium hydroxide and chlorine gas
- d) Sodium chloride and hydrogen gas
Answer: a) Sodium metal and chlorine gas
Explanation: During the electrolysis of molten NaCl, sodium metal is formed at the cathode, and chlorine gas is produced at the anode.
25. The main difference between a galvanic and electrolytic cell is that:
- a) A galvanic cell generates electrical energy, while an electrolytic cell requires electrical energy to function
- b) A galvanic cell operates under non-spontaneous conditions, while an electrolytic cell operates spontaneously
- c) Both cells require an external power source to function
- d) In both cells, the anode is positive
Answer: a) A galvanic cell generates electrical energy, while an electrolytic cell requires electrical energy to function
Explanation: A galvanic cell converts chemical energy into electrical energy spontaneously, while an electrolytic cell requires external electrical energy to drive a non-spontaneous reaction.
26. The voltage of a galvanic cell is called:
- a) Electromotive force (EMF)
- b) Current
- c) Resistance
- d) Power
Answer: a) Electromotive force (EMF)
Explanation: The voltage of a galvanic cell is known as its electromotive force (EMF), which is the potential difference between the two electrodes when no current is flowing.
27. The Nernst equation is used to calculate:
- a) The cell potential under non-standard conditions
- b) The resistance of the cell
- c) The current flowing through the cell
- d) The concentration of electrolytes
Answer: a) The cell potential under non-standard conditions
Explanation: The Nernst equation relates the cell potential to the standard electrode potential, temperature, and the concentrations of the reactants and products.
28. Which of the following factors affects the electrode potential of a half-cell?
- a) Temperature
- b) Concentration of ions
- c) Nature of the electrode
- d) All of the above
Answer: d) All of the above
Explanation: The electrode potential of a half-cell is influenced by temperature, concentration of the ions in the solution, and the material of the electrode.
29. The half-cell reaction at the cathode in a hydrogen fuel cell is:
- a) 2H₂ → 4H⁺ + 4e⁻
- b) O₂ + 4H⁺ + 4e⁻ → 2H₂O
- c) O₂ + 2H⁺ → H₂O₂
- d) H₂ → 2H⁺ + 2e⁻
Answer: b) O₂ + 4H⁺ + 4e⁻ → 2H₂O
Explanation: In a hydrogen fuel cell, oxygen is reduced at the cathode, combining with protons (H⁺) and electrons to form water.
30. What happens to the mass of the anode in a galvanic cell during operation?
- a) It decreases
- b) It increases
- c) It remains constant
- d) It depends on the electrolyte
Answer: a) It decreases
Explanation: In a galvanic cell, the anode undergoes oxidation, meaning the metal loses electrons and dissolves into the electrolyte, leading to a decrease in mass.
31. Which of the following statements about a concentration cell is true?
- a) It has identical electrodes and electrolytes but different concentrations
- b) It operates on a temperature difference between the two half-cells
- c) It produces electrical energy through fuel combustion
- d) The cell potential is always zero
Answer: a) It has identical electrodes and electrolytes but different concentrations
Explanation: A concentration cell consists of two half-cells with the same electrodes and electrolytes, but different ion concentrations. The cell potential arises due to this concentration difference.
32. Which substance is typically used as the electrolyte in a nickel-cadmium battery?
- a) Sulfuric acid
- b) Potassium hydroxide
- c) Ammonium chloride
- d) Sodium chloride
Answer: b) Potassium hydroxide
Explanation: Nickel-cadmium batteries use an alkaline electrolyte, typically potassium hydroxide (KOH), to facilitate the electrochemical reactions.
33. Which of the following metals will NOT corrode in moist air?
- a) Zinc
- b) Aluminum
- c) Gold
- d) Iron
Answer: c) Gold
Explanation: Gold is highly resistant to corrosion due to its very low reactivity, making it one of the least reactive metals in air or water.
34. In the electrolysis of water, which gas is produced at the anode?
- a) Hydrogen
- b) Oxygen
- c) Chlorine
- d) Nitrogen
Answer: b) Oxygen
Explanation: During the electrolysis of water, oxygen gas is produced at the anode due to the oxidation of water molecules (2H₂O → O₂ + 4H⁺ + 4e⁻).
35. The electrode potential of the standard hydrogen electrode (SHE) is:
- a) 1V
- b) 0V
- c) -1V
- d) +1.5V
Answer: b) 0V
Explanation: The standard hydrogen electrode (SHE) is defined to have an electrode potential of exactly 0V, and it serves as the reference for measuring the potentials of other electrodes.
36. Corrosion of metals is an example of:
- a) Oxidation reaction
- b) Reduction reaction
- c) Decomposition reaction
- d) Acid-base reaction
Answer: a) Oxidation reaction
Explanation: Corrosion occurs when a metal is oxidized, losing electrons and reacting with environmental agents like oxygen and moisture.
37. The cathode material used in a lithium-ion battery is typically:
- a) Nickel
- b) Graphite
- c) Lithium cobalt oxide
- d) Lead dioxide
Answer: c) Lithium cobalt oxide
Explanation: In most lithium-ion batteries, lithium cobalt oxide (LiCoO₂) is used as the cathode material, providing high energy density.
38. The direction of current in an electrolytic cell is:
- a) From cathode to anode in the external circuit
- b) From anode to cathode in the external circuit
- c) From electrolyte to the electrodes
- d) From the salt bridge to the electrodes
Answer: b) From anode to cathode in the external circuit
Explanation: In an electrolytic cell, current flows from the positive anode to the negative cathode in the external circuit.
39. Which metal is commonly used for galvanizing iron to prevent corrosion?
- a) Zinc
- b) Aluminum
- c) Copper
- d) Lead
Answer: a) Zinc
Explanation: Zinc is commonly used to coat iron in the galvanization process, protecting the iron from rusting by acting as a sacrificial anode.
40. In a fuel cell, which of the following is consumed as a fuel?
- a) Oxygen
- b) Hydrogen
- c) Methane
- d) Water
Answer: b) Hydrogen
Explanation: In a hydrogen fuel cell, hydrogen is the primary fuel that reacts with oxygen to generate electricity, with water as the byproduct.
41. The potential of a galvanic cell is directly proportional to:
- a) The number of electrons transferred
- b) The concentration of the electrolytes
- c) The distance between the electrodes
- d) The surface area of the electrodes
Answer: b) The concentration of the electrolytes
Explanation: According to the Nernst equation, the potential of a galvanic cell depends on the concentrations of the reactants and products in the cell.
42. Which of the following is a primary cell?
- a) Lead-acid battery
- b) Nickel-cadmium battery
- c) Dry cell
- d) Lithium-ion battery
Answer: c) Dry cell
Explanation: A dry cell is a primary cell that is not rechargeable. Once its chemicals are used up, it cannot be reused.
43. The electrolyte in a molten sodium chloride electrolytic cell is:
- a) Sodium hydroxide
- b) Sodium chloride
- c) Sodium metal
- d) Sodium carbonate
Answer: b) Sodium chloride
Explanation: In the electrolysis of molten sodium chloride (NaCl), the electrolyte is molten NaCl, which decomposes into sodium metal and chlorine gas.
44. During the corrosion of iron, which of the following is produced at the cathodic region?
- a) Fe²⁺ ions
- b) OH⁻ ions
- c) Fe³⁺ ions
- d) H₂ gas
Answer: b) OH⁻ ions
Explanation: In the corrosion process, hydroxide ions (OH⁻) are formed in the cathodic region as oxygen is reduced, contributing to the formation of rust (Fe(OH)₃).
45. Which of the following materials is used as the anode in a common alkaline battery?
- a) Zinc
- b) Copper
- c) Lead
- d) Silver
Answer: a) Zinc
Explanation: In an alkaline battery, the anode is made of zinc, and it undergoes oxidation to generate electrical energy.
46. The standard electrode potential for a half-reaction is measured relative to:
- a) Standard hydrogen electrode (SHE)
- b) Calomel electrode
- c) Silver-silver chloride electrode
- d) Platinum electrode
Answer: a) Standard hydrogen electrode (SHE)
Explanation: The standard electrode potential of a half-reaction is measured relative to the standard hydrogen electrode (SHE), which has a potential of 0V.
47. In a lead-acid battery, the electrolyte used is:
- a) Sulfuric acid
- b) Hydrochloric acid
- c) Nitric acid
- d) Phosphoric acid
Answer: a) Sulfuric acid
Explanation: A lead-acid battery uses sulfuric acid as the electrolyte, which facilitates the electrochemical reactions between the lead and lead dioxide electrodes.
48. Which metal is used as the cathode in a copper refining electrolytic cell?
- a) Copper
- b) Zinc
- c) Iron
- d) Silver
Answer: a) Copper
Explanation: In the electrolytic refining of copper, a pure copper cathode is used, and copper ions from the anode are deposited on the cathode during the process.
49. Which of the following statements about fuel cells is correct?
- a) Fuel cells convert chemical energy into electrical energy continuously
- b) Fuel cells can only be used once
- c) Fuel cells store electrical energy like batteries
- d) Fuel cells require a solid fuel to operate
Answer: a) Fuel cells convert chemical energy into electrical energy continuously
Explanation: Fuel cells continuously convert chemical energy into electrical energy as long as fuel and an oxidant are supplied, without needing recharging.
50. The Daniell cell consists of which of the following electrodes?
- a) Zinc and copper
- b) Iron and silver
- c) Nickel and zinc
- d) Copper and magnesium
Answer: a) Zinc and copper
Explanation: A Daniell cell consists of a zinc electrode in zinc sulfate solution and a copper electrode in copper sulfate solution, generating a potential difference between the two.
51. Which of the following is a secondary cell?
- a) Zinc-carbon cell
- b) Lead-acid battery
- c) Silver oxide battery
- d) Mercury cell
Answer: b) Lead-acid battery
Explanation: A secondary cell is rechargeable, and a lead-acid battery can be recharged by reversing the chemical reactions that occur during discharge.
52. In a galvanic cell, the oxidation half-reaction occurs at:
- a) The cathode
- b) The anode
- c) The salt bridge
- d) Both electrodes
Answer: b) The anode
Explanation: In a galvanic cell, oxidation (loss of electrons) occurs at the anode, which is negatively charged.
53. A Daniel cell can be represented as:
- a) Zn | Zn²⁺ || Cu²⁺ | Cu
- b) Cu | Cu²⁺ || Zn²⁺ | Zn
- c) Zn | Cu || Zn²⁺ | Cu²⁺
- d) Cu²⁺ | Cu || Zn²⁺ | Zn
Answer: a) Zn | Zn²⁺ || Cu²⁺ | Cu
Explanation: The anode (Zn) is on the left and the cathode (Cu) is on the right, separated by a salt bridge represented by the double vertical lines.
54. The overall reaction for a lead-acid storage battery during discharge is:
- a) Pb + PbO₂ + 2H₂SO₄ → 2PbSO₄ + 2H₂O
- b) PbSO₄ + H₂O → Pb + H₂SO₄
- c) Pb + PbSO₄ → 2PbSO₄
- d) Pb + H₂SO₄ → PbO₂ + Pb
Answer: a) Pb + PbO₂ + 2H₂SO₄ → 2PbSO₄ + 2H₂O
Explanation: During discharge, lead and lead dioxide react with sulfuric acid to form lead sulfate and water, releasing electrical energy.
55. In an electrochemical series, metals with a higher negative reduction potential:
- a) Are more easily oxidized
- b) Are more easily reduced
- c) Do not undergo reactions
- d) Have a lower tendency to lose electrons
Answer: a) Are more easily oxidized
Explanation: Metals with more negative reduction potentials are more likely to lose electrons and undergo oxidation.
56. Which of the following reactions occurs at the cathode in a lead-acid battery during discharge?
- a) PbO₂ + 4H⁺ + SO₄²⁻ + 2e⁻ → PbSO₄ + 2H₂O
- b) Pb → Pb²⁺ + 2e⁻
- c) 2H₂O → O₂ + 4H⁺ + 4e⁻
- d) PbSO₄ + 2H₂O → Pb + H₂SO₄
Answer: a) PbO₂ + 4H⁺ + SO₄²⁻ + 2e⁻ → PbSO₄ + 2H₂O
Explanation: In a lead-acid battery, lead dioxide (PbO₂) is reduced to lead sulfate (PbSO₄) at the cathode during discharge.
57. Which statement is true for the corrosion of iron?
- a) Oxidation occurs at the anode
- b) Oxidation occurs at the cathode
- c) The iron metal acts as a cathode
- d) The corrosion process does not involve any electron transfer
Answer: a) Oxidation occurs at the anode
Explanation: In the corrosion of iron, iron is oxidized to Fe²⁺ at the anode, while oxygen is reduced at the cathode.
58. The unit of cell potential is:
- a) Ohm
- b) Ampere
- c) Volt
- d) Coulomb
Answer: c) Volt
Explanation: The unit of cell potential (or electromotive force, EMF) is the volt, which represents the potential difference between the two electrodes.
59. What is the product at the cathode during the electrolysis of molten NaCl?
- a) Sodium
- b) Chlorine
- c) Oxygen
- d) Hydrogen
Answer: a) Sodium
Explanation: During the electrolysis of molten sodium chloride (NaCl), sodium metal is produced at the cathode.
60. The standard cell potential for a reaction can be calculated using:
- a) Nernst equation
- b) Gibbs free energy equation
- c) Faraday’s laws of electrolysis
- d) The standard reduction potentials of the half-reactions
Answer: d) The standard reduction potentials of the half-reactions
Explanation: The standard cell potential is calculated as the difference between the standard reduction potentials of the cathode and anode half-reactions.
61. In a hydrogen-oxygen fuel cell, the overall reaction is:
- a) 2H₂ + O₂ → 2H₂O
- b) 2H₂ + O₂ → H₂O₂
- c) H₂O → H₂ + O₂
- d) H₂ + O₂ → H₂O
Answer: a) 2H₂ + O₂ → 2H₂O
Explanation: In a hydrogen-oxygen fuel cell, hydrogen reacts with oxygen to form water, producing electrical energy.
62. In an electrochemical cell, the salt bridge:
- a) Allows for the transfer of electrons
- b) Completes the electrical circuit by allowing ions to flow
- c) Provides the voltage difference
- d) Provides a solid electrolyte
Answer: b) Completes the electrical circuit by allowing ions to flow
Explanation: The salt bridge allows the movement of ions to maintain charge neutrality and completes the electrical circuit in an electrochemical cell.
63. Which of the following ions migrates towards the anode during the electrolysis of an aqueous NaCl solution?
- a) Na⁺
- b) Cl⁻
- c) OH⁻
- d) H⁺
Answer: b) Cl⁻
Explanation: During the electrolysis of aqueous NaCl, chloride ions (Cl⁻) migrate towards the anode, where they are oxidized to form chlorine gas.
64. In the electrolysis of water, what is the ratio of hydrogen to oxygen gases produced?
- a) 1:1
- b) 2:1
- c) 1:2
- d) 3:2
Answer: b) 2:1
Explanation: The electrolysis of water produces hydrogen and oxygen gases in a 2:1 ratio (2H₂O → 2H₂ + O₂).
65. In an electrochemical cell, the anode is the site of:
- a) Oxidation
- b) Reduction
- c) Electron gain
- d) Salt bridge formation
Answer: a) Oxidation
Explanation: In an electrochemical cell, oxidation (loss of electrons) occurs at the anode.
66. Which metal is deposited at the cathode during the electrolysis of copper(II) sulfate solution using copper electrodes?
- a) Zinc
- b) Copper
- c) Silver
- d) Iron
Answer: b) Copper
Explanation: During the electrolysis of copper(II) sulfate solution with copper electrodes, copper ions are reduced and deposited at the cathode.
67. The electrode where reduction occurs in an electrochemical cell is called:
- a) Cathode
- b) Anode
- c) Electrolyte
- d) Salt bridge
Answer: a) Cathode
Explanation: Reduction (gain of electrons) occurs at the cathode in both galvanic and electrolytic cells.
68. The relationship between Gibbs free energy (ΔG) and cell potential (E) is given by:
- a) ΔG = nFE
- b) ΔG = -nFE
- c) ΔG = -E/nF
- d) ΔG = E/nF
Answer: b) ΔG = -nFE
Explanation: The relationship between Gibbs free energy and cell potential is ΔG = -nFE, where n is the number of moles of electrons, F is Faraday’s constant, and E is the cell potential.
71. In a galvanic cell, the salt bridge contains:
- a) A solution of strong acids
- b) A solution of electrolytes
- c) A solution of reducing agents
- d) Pure water
Answer: b) A solution of electrolytes
Explanation: The salt bridge in a galvanic cell contains an electrolyte solution (usually KCl or NaCl) that helps maintain charge neutrality by allowing the flow of ions.
72. The electrolysis of molten aluminum oxide involves the use of:
- a) Copper electrodes
- b) Iron electrodes
- c) Graphite electrodes
- d) Silver electrodes
Answer: c) Graphite electrodes
Explanation: In the electrolysis of molten aluminum oxide (Al₂O₃), graphite electrodes are used due to their ability to withstand high temperatures and act as an inert conductor.
73. Which of the following is the main advantage of a fuel cell over a conventional battery?
- a) Higher voltage output
- b) Continuous energy supply as long as fuel is provided
- c) Faster rate of chemical reactions
- d) Cheaper to produce
Answer: b) Continuous energy supply as long as fuel is provided
Explanation: Fuel cells can continuously generate electricity as long as fuel (such as hydrogen) and an oxidizing agent (such as oxygen) are supplied, unlike batteries, which store a fixed amount of energy.
74. Which of the following metals is the best reducing agent according to the electrochemical series?
- a) Lithium
- b) Sodium
- c) Zinc
- d) Copper
Answer: a) Lithium
Explanation: Lithium has the most negative standard reduction potential in the electrochemical series, making it the strongest reducing agent.
75. Which electrolyte is used in a molten carbonate fuel cell (MCFC)?
- a) Potassium hydroxide
- b) Sodium chloride
- c) Molten lithium carbonate
- d) Sulfuric acid
Answer: c) Molten lithium carbonate
Explanation: In a molten carbonate fuel cell (MCFC), molten lithium carbonate is used as the electrolyte, allowing for high-temperature operation.
76. Which of the following processes leads to the protection of metals by the formation of a thin oxide layer?
- a) Cathodic protection
- b) Galvanizing
- c) Anodizing
- d) Electroplating
Answer: c) Anodizing
Explanation: Anodizing is a process that increases the thickness of the natural oxide layer on the surface of metals like aluminum, providing corrosion resistance.
77. Which of the following elements is used as a cathode material in a standard hydrogen electrode (SHE)?
- a) Platinum
- b) Gold
- c) Copper
- d) Silver
Answer: a) Platinum
Explanation: Platinum is used as the inert cathode material in a standard hydrogen electrode (SHE) because it facilitates the exchange of electrons without reacting with hydrogen gas.
78. Which of the following is used as a reducing agent in a blast furnace during iron extraction?
- a) Oxygen
- b) Carbon monoxide
- c) Carbon dioxide
- d) Hydrogen
Answer: b) Carbon monoxide
Explanation: In the blast furnace, carbon monoxide acts as the reducing agent that reduces iron ore (Fe₂O₃) to metallic iron (Fe).
79. The electrochemical cell in which both electrodes are made of the same material but differ in ion concentration is known as:
- a) A galvanic cell
- b) An electrolytic cell
- c) A concentration cell
- d) A fuel cell
Answer: c) A concentration cell
Explanation: In a concentration cell, the electrodes are the same, but the ion concentrations in the electrolytes differ, creating a potential difference.
80. In a galvanic cell, the positive terminal is the:
- a) Cathode
- b) Anode
- c) Salt bridge
- d) Electrolyte
Answer: a) Cathode
Explanation: In a galvanic cell, the cathode is the positive terminal because it attracts electrons, and reduction occurs at this electrode.
81. Which of the following metals is commonly used in electroplating to protect steel from corrosion?
- a) Lead
- b) Zinc
- c) Copper
- d) Aluminum
Answer: b) Zinc
Explanation: Zinc is commonly used to electroplate steel to protect it from corrosion through a process called galvanization.
82. The standard electrode potential of a hydrogen electrode is assigned a value of:
- a) 1V
- b) -1V
- c) 0V
- d) +1V
Answer: c) 0V
Explanation: The standard hydrogen electrode (SHE) is defined to have a standard electrode potential of exactly 0V, and it serves as the reference point for measuring other electrode potentials.
83. In an electrolytic cell, the cathode is:
- a) Positively charged
- b) Negatively charged
- c) Neutral
- d) Dependent on the electrolyte
Answer: b) Negatively charged
Explanation: In an electrolytic cell, the cathode is negatively charged because it attracts cations (positive ions) for reduction.
84. Which metal is commonly used for the cathode in a nickel-cadmium battery?
- a) Nickel oxide
- b) Zinc oxide
- c) Copper oxide
- d) Silver oxide
Answer: a) Nickel oxide
Explanation: In a nickel-cadmium battery, the cathode material is typically nickel oxide hydroxide (NiOOH), which undergoes reduction during discharge.
85. What is the function of the porous partition in a Leclanché cell?
- a) To allow ions to pass between electrodes
- b) To prevent electron flow
- c) To separate different chemicals
- d) To prevent gases from escaping
Answer: a) To allow ions to pass between electrodes
Explanation: The porous partition in a Leclanché cell allows ions to pass between the electrodes while preventing the mixing of chemicals that could cause short-circuiting.
86. Which of the following gases is released at the anode during the electrolysis of molten sodium chloride?
- a) Oxygen
- b) Chlorine
- c) Hydrogen
- d) Nitrogen
Answer: b) Chlorine
Explanation: During the electrolysis of molten sodium chloride, chlorine gas is released at the anode due to the oxidation of chloride ions.
87. Which type of electrolyte is used in a lead-acid storage battery?
- a) Hydrochloric acid
- b) Sulfuric acid
- c) Nitric acid
- d) Acetic acid
Answer: b) Sulfuric acid
Explanation: Lead-acid storage batteries use sulfuric acid (H₂SO₄) as the electrolyte, which facilitates the electrochemical reactions between the lead and lead dioxide electrodes.
88. Which of the following is the correct expression for Faraday’s second law of electrolysis?
- a) The amount of substance deposited is directly proportional to the current
- b) The mass of the substance deposited is directly proportional to the charge
- c) The mass of the substance deposited is directly proportional to the equivalent weight
- d) The equivalent weight of the substance deposited is directly proportional to the number of electrons involved
Answer: c) The mass of the substance deposited is directly proportional to the equivalent weight
Explanation: Faraday’s second law of electrolysis states that the mass of the substance deposited or liberated at an electrode is directly proportional to its equivalent weight.
89. The standard cell potential of a galvanic cell is:
- a) Always negative
- b) Always positive
- c) Zero
- d) Dependent on the reaction conditions
Answer: b) Always positive
Explanation: The standard cell potential of a galvanic cell is always positive, indicating a spontaneous reaction.
90. Which of the following materials is commonly used as the cathode in an alkaline battery?
- a) Zinc
- b) Copper
- c) Manganese dioxide
- d) Nickel oxide
Answer: c) Manganese dioxide
Explanation: In alkaline batteries, manganese dioxide (MnO₂) is used as the cathode material, where it undergoes reduction during discharge.
91. The Nernst equation relates the cell potential to:
- a) Temperature
- b) Concentration of reactants and products
- c) Pressure
- d) Both a and b
Answer: d) Both a and b
Explanation: The Nernst equation relates the cell potential to temperature and the concentrations of the reactants and products, allowing the calculation of the cell potential under non-standard conditions.
92. Which of the following ions is responsible for the corrosion of iron?
- a) Chloride ions
- b) Sodium ions
- c) Sulfate ions
- d) Nitrate ions
Answer: a) Chloride ions
Explanation: Chloride ions (Cl⁻) are highly corrosive to metals like iron because they accelerate the oxidation process, leading to rust formation.
93. What is the major disadvantage of a lithium-ion battery?
- a) High self-discharge rate
- b) Limited charge cycles
- c) Prone to memory effect
- d) High cost
Answer: d) High cost
Explanation: While lithium-ion batteries are highly efficient and have long charge cycles, their high cost is a major disadvantage compared to other types of batteries.
94. Which of the following methods is used to prevent the corrosion of iron?
- a) Galvanization
- b) Oxidation
- c) Reduction
- d) Electrolysis
Answer: a) Galvanization
Explanation: Galvanization involves coating iron or steel with a layer of zinc to prevent corrosion.
95. The rate of corrosion is least in:
- a) Dry air
- b) Wet air
- c) Saltwater
- d) Moist air
Answer: a) Dry air
Explanation: Corrosion occurs faster in the presence of moisture and electrolytes. Dry air has the least moisture and hence the least corrosion rate.
96. The emf of a standard cell depends on:
- a) The nature of the electrodes and electrolytes
- b) The current flowing through the cell
- c) The size of the electrodes
- d) The resistance of the cell
Answer: a) The nature of the electrodes and electrolytes
Explanation: The electromotive force (emf) of a standard cell depends on the nature of the electrodes and the electrolytes used in the cell.
97. The amount of charge required to deposit 1 mole of a substance at an electrode during electrolysis is given by:
- a) Faraday’s constant
- b) Avogadro’s number
- c) Coulomb’s law
- d) Planck’s constant
Answer: a) Faraday’s constant
Explanation: Faraday’s constant (approximately 96,500 C/mol) represents the amount of charge required to deposit 1 mole of a substance during electrolysis.
98. Which of the following reactions occurs at the cathode in an electrochemical cell?
- a) Oxidation
- b) Reduction
- c) Electron loss
- d) Proton transfer
Answer: b) Reduction
Explanation: In an electrochemical cell, reduction (gain of electrons) occurs at the cathode.
99. In a fuel cell, the oxidizing agent is typically:
- a) Oxygen
- b) Hydrogen
- c) Nitrogen
- d) Carbon dioxide
Answer: a) Oxygen
Explanation: In most fuel cells, oxygen acts as the oxidizing agent, accepting electrons to form water as a product.
100. What is the purpose of the salt bridge in a galvanic cell?
- a) To maintain electrical neutrality in the solution
- b) To increase the cell voltage
- c) To separate the anode and cathode physically
- d) To allow the flow of electrons between electrodes
Answer: a) To maintain electrical neutrality in the solution
Explanation: The salt bridge allows ions to flow between the two half-cells to maintain charge balance, ensuring the continuous flow of electrons and maintaining the cell’s electrical neutrality
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