Electrochemical cells electrode potentials Nernst equation and fuel cells - Question Bank

1. Which of the following statements about electrode potentials is correct?
A) Oxidation potential is always equal to reduction potential.
B) Oxidation potential is the negative of the reduction potential for the same electrode.
C) Oxidation potential is always greater than reduction potential.
D) Oxidation potential is always less than reduction potential.
2. A fuel cell that uses molten carbonate as an electrolyte operates at high temperatures. This is typically a:
A) Proton Exchange Membrane (PEM) fuel cell
B) Solid Oxide Fuel Cell (SOFC)
C) Alkaline Fuel Cell (AFC)
D) Phosphoric Acid Fuel Cell (PAFC)
3. The Nernst equation is essential for understanding:
A) Only standard electrode potentials
B) How electrode potentials change with concentration
C) The physical properties of metals
D) The chemical bonding in molecules
4. If the reaction quotient Q is very large, the electrode potential E will be:
A) Close to E°
B) Significantly lower than E°
C) Significantly higher than E°
D) Zero
5. What is the main reason for using catalytic electrodes in fuel cells?
A) To increase resistance
B) To decrease the rate of reaction
C) To increase the rate of electrochemical reactions
D) To act as insulators
6. The potential difference that drives the flow of electrons in the external circuit is called:
A) Electrode potential
B) Cell potential (EMF)
C) Standard potential
D) Ionic potential
7. Which of the following is a disadvantage of hydrogen as a fuel in fuel cells?
A) It is abundant.
B) It is non-polluting.
C) It is difficult to store and transport.
D) It has high energy density.
8. If Q < 1 in the Nernst equation, the term -(RT/nF) ln Q will be:
A) Negative
B) Positive
C) Zero
D) Indeterminate
9. What is the role of electrons in the external circuit of an electrochemical cell?
A) They are carried by ions.
B) They flow from the cathode to the anode.
C) They flow from the anode to the cathode.
D) They are consumed in the electrolyte.
10. The Nernst equation can be used to calculate the cell potential under conditions of:
A) Standard temperature and pressure only
B) Non-standard temperature and pressure
C) Equilibrium
D) Zero Gibbs free energy change
11. Which of the following is a characteristic of a fuel cell that makes it environmentally friendly?
A) It produces greenhouse gases.
B) Its primary emission is water.
C) It requires large amounts of fossil fuels.
D) Its efficiency is very low.
12. What is the unit of electrode potential?
A) Ampere
B) Volt
C) Ohm
D) Coulomb
13. The standard reduction potential of Cu²⁺/Cu is +0.34 V and that of Zn²⁺/Zn is -0.76 V. The standard cell potential (E°_cell) for the reaction Zn + Cu²⁺ → Zn²⁺ + Cu is:
A) +0.42 V
B) -0.42 V
C) +1.10 V
D) -1.10 V
14. What happens to the electrode potential of a metal when its cation concentration in solution decreases?
A) It increases
B) It decreases
C) It remains the same
D) It becomes zero
15. In an electrolytic cell, the cathode is connected to the:
A) Positive terminal of the power supply
B) Negative terminal of the power supply
C) External circuit
D) Electrolyte
16. In an electrolytic cell, the anode is connected to the:
A) Negative terminal of the power supply
B) Positive terminal of the power supply
C) Battery
D) Galvanometer
17. Which of the following is NOT a factor affecting electrode potential?
A) Concentration of ions
B) Temperature
C) Pressure of gases
D) Color of the solution
18. The relationship between E°_cell and K at 298 K is given by:
A) E°_cell = (RT/nF) ln K
B) E°_cell = (2.303RT/nF) log K
C) E°_cell = (0.0591/n) log K
D) E°_cell = -(0.0591/n) log K
19. What is the equilibrium constant (K) for a redox reaction when E_cell = 0?
A) K < 1
B) K > 1
C) K = 1
D) K is undefined
20. If E°_cell is positive, the reaction is:
A) Non-spontaneous under standard conditions
B) Spontaneous under standard conditions
C) At equilibrium under standard conditions
D) Impossible under standard conditions
21. Electrode potential is an intensive property. What does this mean?
A) It depends on the amount of substance.
B) It does not depend on the amount of substance.
C) It is always zero.
D) It is always positive.
22. What is the primary component of the electrolyte in many alkaline hydrogen-oxygen fuel cells?
A) Sulfuric acid
B) Potassium hydroxide solution
C) Sodium chloride solution
D) Distilled water
23. In a fuel cell, the electrodes are typically made of:
A) Glass
B) Platinum or other catalytic materials
C) Wood
D) Plastic
24. The Nernst equation is derived from which thermodynamic relationship?
A) ΔG = -nFE_cell
B) ΔG° = -nFE°_cell
C) ΔG = ΔH - TΔS
D) PV = nRT
25. For the reaction Mⁿ⁺ + ne⁻ → M, if the concentration of Mⁿ⁺ increases, the electrode potential (E) will:
A) Increase
B) Decrease
C) Remain unchanged
D) Become zero
26. The standard cell potential (E°_cell) of a galvanic cell is calculated as:
A) E°_cathode - E°_anode
B) E°_anode - E°_cathode
C) E°_cathode + E°_anode
D) E°_anode + E°_cathode
27. In the Daniell cell (Zn | Zn²⁺ || Cu²⁺ | Cu), what is the cathode reaction?
A) Zn(s) → Zn²⁺(aq) + 2e⁻
B) Cu²⁺(aq) + 2e⁻ → Cu(s)
C) Zn²⁺(aq) + 2e⁻ → Zn(s)
D) Cu(s) → Cu²⁺(aq) + 2e⁻
28. Consider the Daniell cell: Zn(s) | Zn²⁺(aq) || Cu²⁺(aq) | Cu(s). What is the anode reaction?
A) Zn²⁺(aq) + 2e⁻ → Zn(s)
B) Cu²⁺(aq) + 2e⁻ → Cu(s)
C) Zn(s) → Zn²⁺(aq) + 2e⁻
D) Cu(s) → Cu²⁺(aq) + 2e⁻
29. What is the purpose of the salt bridge in a galvanic cell?
A) To increase the voltage
B) To provide a path for electron flow
C) To complete the internal circuit by allowing ion migration
D) To act as the site of oxidation
30. Which of the following is a characteristic of a galvanic cell?
A) It uses electrical energy to drive a non-spontaneous reaction.
B) It converts chemical energy into electrical energy.
C) The anode is the site of reduction.
D) The cathode is the site of oxidation.
31. If a half-reaction has a standard reduction potential of +0.80 V, it is more likely to be reduced than a half-reaction with a standard reduction potential of:
A) +1.20 V
B) +0.34 V
C) +0.80 V
D) +0.90 V
32. What is the standard electrode potential for the reduction of H⁺ to H₂ (SHE - Standard Hydrogen Electrode)?
A) 1.00 V
B) -0.00 V
C) 0.00 V
D) 0.50 V
33. The electromotive force (EMF) of a fuel cell is generally:
A) Independent of the fuel and oxidant
B) Dependent on the type of fuel and oxidant
C) Always 1.1 V
D) Zero at standard conditions
34. Which species is reduced at the cathode of a hydrogen-oxygen fuel cell (alkaline electrolyte)?
A) H₂
B) O₂
C) H₂O
D) H⁺
35. Which species is oxidized at the anode of a hydrogen-oxygen fuel cell?
A) O₂
B) H₂O
C) H₂
D) OH⁻
36. What is the main advantage of using fuel cells over conventional combustion engines?
A) Higher cost of production
B) Lower efficiency
C) Reduced pollution and higher efficiency
D) Limited lifespan
37. In a hydrogen-oxygen fuel cell, what is the overall reaction?
A) 2H₂ + O₂ → 2H₂O
B) H₂ + O₂ → H₂O₂
C) 2H₂O → 2H₂ + O₂
D) H₂O₂ → H₂O + ½O₂
38. Which of the following is a common fuel used in fuel cells?
A) Methane
B) Hydrogen
C) Propane
D) Butane
39. A fuel cell is a type of electrochemical cell that:
A) Stores electrical energy
B) Converts chemical energy from a fuel into electrical energy
C) Uses electrical energy to produce fuel
D) Generates heat rather than electricity
40. What is the relationship between the cell potential (E_cell) and the standard cell potential (E°_cell) at non-standard conditions?
A) E_cell = E°_cell - (RT/nF) ln Q
B) E_cell = E°_cell + (RT/nF) ln Q
C) E_cell = E°_cell - (2.303RT/nF) log Q
D) E_cell = E°_cell + (2.303RT/nF) log Q
41. If the concentration of products is higher than reactants (Q > 1), the electrode potential (E) will:
A) Increase
B) Decrease
C) Remain the same
D) Become zero
42. What does 'n' represent in the Nernst equation?
A) The number of moles of reactants
B) The number of moles of products
C) The number of electrons transferred in the redox reaction
D) The number of half-cells in the electrochemical cell
43. At 298 K, the Nernst equation can be simplified to:
A) E = E° - (0.0591/n) log Q
B) E = E° + (0.0591/n) log Q
C) E = E° - (0.0591/n) ln Q
D) E = E° + (0.0591/n) ln Q
44. What is the Nernst equation for a single electrode at 298 K?
A) E = E° - (RT/nF) ln Q
B) E = E° + (RT/nF) ln Q
C) E = E° - (2.303RT/nF) log Q
D) E = E° + (2.303RT/nF) log Q
45. The Nernst equation relates the electrode potential to:
A) Temperature and pressure only
B) Concentration of reactants and products
C) Standard electrode potential and reaction quotient
D) The number of electrons transferred and the Faraday constant
46. Which of the following statements is true for a spontaneous redox reaction in an electrochemical cell?
A) The cell potential (E_cell) is negative
B) The Gibbs free energy change (ΔG) is positive
C) The cell potential (E_cell) is positive
D) The reaction quotient (Q) is equal to the equilibrium constant (K)
47. What is the standard electrode potential (E°)?
A) The potential of an electrode at any concentration and temperature
B) The potential of an electrode at 25°C and 1 atm pressure
C) The potential of an electrode at standard conditions (298 K, 1 atm, 1 M concentration)
D) The potential difference between two electrodes at equilibrium
48. Reduction occurs at which electrode in an electrochemical cell?
A) Anode
B) Cathode
C) Working electrode
D) Reference electrode
49. In an electrochemical cell, which electrode is the site of oxidation?
A) Cathode
B) Anode
C) Salt bridge
D) Electrolyte
50. What is the primary function of an electrochemical cell?
A) To generate electrical energy from chemical reactions
B) To use electrical energy to drive non-spontaneous chemical reactions
C) To measure the rate of chemical reactions
D) To determine the equilibrium constant of reactions
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