CBSE Class 12 MCQs Chemistry Chapter 3 Electrochemistry

Class 12^th Chemistry Chapter MCQs

1. Which of the following is a type of electrochemical cell?

a) Galvanic cell
b) Electrolytic cell
c) Both a and b
d) None of the above

Answer: c) Both a and b
Explanation: A galvanic cell produces electrical energy from chemical reactions, while an electrolytic cell uses electrical energy to drive non-spontaneous reactions.

2. Which of the following represents the standard electrode potential of a half-cell?

a) $E^o_{\text{cell}}$
b) $E^o_{\text{half}}$
c) $\Delta G^o$
d) $E_{\text{red}}$

Answer: b) $E^o_{\text{half}}$
Explanation: The standard electrode potential ( $E^o_{\text{half}}$ ) is the potential difference for a half-reaction under standard conditions.

3. In an electrochemical cell, the anode is the site of:

a) Reduction
b) Oxidation
c) Both reduction and oxidation
d) None of the above

Answer: b) Oxidation
Explanation: In an electrochemical cell, oxidation occurs at the anode, where electrons are lost.

4. The standard electrode potential for a reduction reaction is given as:

a) $E^o_{\text{red}}$
b) $E^o_{\text{cell}}$
c) $\Delta G^o$
d) $E^o_{\text{oxid}}$

Answer: a) $E^o_{\text{red}}$
Explanation: The standard electrode potential for reduction is denoted as $E^o_{\text{red}}$ , which refers to the potential for a species to gain electrons under standard conditions.

5. Which of the following is the correct relationship between Gibbs free energy and cell potential?

a) $\Delta G = -nFE_{\text{cell}}$
b) $\Delta G = nFE_{\text{cell}}$
c) $\Delta G = -nFE^o_{\text{cell}}$
d) $\Delta G = -nF$

Answer: a) $\Delta G = -nFE_{\text{cell}}$
Explanation: The relationship between Gibbs free energy ( $\Delta G$ ) and the cell potential ( $E_{\text{cell}}$ ) is $\Delta G = -nFE_{\text{cell}}$ , where $n$ is the number of moles of electrons and $F$ is Faraday's constant.

6. The Nernst equation is used to calculate:

a) Cell potential under non-standard conditions
b) Standard electrode potential
c) Gibbs free energy
d) Both a and b

Answer: a) Cell potential under non-standard conditions
Explanation: The Nernst equation relates the cell potential at non-standard conditions to the standard electrode potential and the concentrations of reactants and products.

7. The cell potential of a galvanic cell is:

a) Always negative
b) Always positive
c) Can be positive or negative
d) Zero at equilibrium

Answer: b) Always positive
Explanation: In a galvanic cell, the cell potential is positive, indicating that the reaction is spontaneous.

8. Which of the following is true for an electrolytic cell?

a) The cell potential is positive
b) The cell potential is negative
c) Electrical energy is converted into chemical energy
d) Chemical energy is converted into electrical energy

Answer: b) The cell potential is negative
Explanation: In an electrolytic cell, electrical energy is used to drive non-spontaneous reactions, and the cell potential is negative.

9. What is the unit of cell potential?

a) Coulomb
b) Ampere
c) Volt
d) Joule

Answer: c) Volt
Explanation: The unit of cell potential is the volt (V), which measures the potential difference between two electrodes.

10. The standard electrode potential for the reduction of hydrogen ions to hydrogen gas is:

a) 0 V
b) 1.23 V
c) -1.23 V
d) 2.71 V

Answer: a) 0 V
Explanation: The standard electrode potential for the reduction of hydrogen ions to hydrogen gas is defined as 0 V at standard conditions (298 K, 1 M concentration, 1 atm pressure).

11. Which of the following statements is true about the electrochemical series?

a) It lists elements in order of their atomic numbers.
b) It lists substances based on their reduction potential.
c) It lists substances based on their oxidation potential.
d) It lists all possible reactions that occur in an electrochemical cell.

Answer: b) It lists substances based on their reduction potential.
Explanation: The electrochemical series lists substances according to their reduction potentials, with the most easily reduced species at the top.

12. In a galvanic cell, the direction of electron flow is from:

a) Anode to cathode
b) Cathode to anode
c) Positive terminal to negative terminal
d) Negative terminal to positive terminal

Answer: a) Anode to cathode
Explanation: In a galvanic cell, electrons flow from the anode (where oxidation occurs) to the cathode (where reduction occurs).

13. Which of the following is true for the cell reaction in a galvanic cell?

a) The total electrode potential is zero.
b) The cell reaction is spontaneous.
c) The cell potential is negative.
d) The electrode potentials are equal.

Answer: b) The cell reaction is spontaneous.
Explanation: In a galvanic cell, the cell reaction is spontaneous, which results in a positive cell potential.

14. Which of the following is used to measure the electrical conductivity of a solution?

a) Voltmeter
b) Conductometer
c) Galvanometer
d) Ammeter

Answer: b) Conductometer
Explanation: A conductometer is used to measure the electrical conductivity of a solution, which is a measure of its ability to conduct electric current.

15. The conductivity of a solution depends on:

a) The concentration of ions
b) The temperature
c) The nature of the solvent
d) All of the above

Answer: d) All of the above
Explanation: The conductivity of a solution depends on the concentration of ions, temperature, and the nature of the solvent.

16. The standard electrode potential of the cell reaction is positive for:

a) Non-spontaneous reactions
b) Spontaneous reactions
c) Both spontaneous and non-spontaneous reactions
d) None of the above

Answer: b) Spontaneous reactions
Explanation: A positive standard electrode potential indicates that the reaction is spontaneous.

17. In which of the following cells does the anode undergo oxidation?

a) Electrolytic cell
b) Galvanic cell
c) Both a and b
d) None of the above

Answer: c) Both a and b
Explanation: In both electrolytic and galvanic cells, the anode undergoes oxidation.

18. Which of the following factors increases the rate of a redox reaction?

a) Decreasing temperature
b) Decreasing the concentration of reactants
c) Increasing temperature
d) Decreasing pressure

Answer: c) Increasing temperature
Explanation: Increasing temperature generally increases the rate of redox reactions by providing more energy for the reactants to overcome the activation energy.

19. Which of the following does NOT affect the electrolysis of water?

a) The concentration of water
b) The temperature
c) The applied voltage
d) The concentration of sulfuric acid

Answer: a) The concentration of water
Explanation: The concentration of water does not significantly affect its electrolysis, but factors like temperature, voltage, and the presence of an electrolyte like sulfuric acid do.

20. In the electrolysis of molten NaCl, which gas is produced at the anode?

a) Chlorine gas
b) Hydrogen gas
c) Oxygen gas
d) Nitrogen gas

Answer: a) Chlorine gas
Explanation: In the electrolysis of molten NaCl, chlorine gas is produced at the anode due to the oxidation of chloride ions.

21. The process of electroplating involves:

a) Oxidation at the cathode
b) Oxidation at the anode
c) Reduction at the cathode
d) Reduction at the anode

Answer: c) Reduction at the cathode
Explanation: In electroplating, the metal ions are reduced at the cathode, where they are deposited as a metal layer.

22. In a galvanic cell, the salt bridge functions to:

a) Prevent the mixing of the two electrolyte solutions
b) Provide ions to maintain electrical neutrality
c) Supply electrons to the anode
d) Both a and b

Answer: d) Both a and b
Explanation: The salt bridge maintains electrical neutrality by providing ions that prevent the mixing of solutions and maintain the charge balance.

23. The concentration cell operates on the principle of:

a) Equal concentrations on both sides
b) Unequal concentrations on both sides
c) No ions involved
d) Both a and c

Answer: b) Unequal concentrations on both sides
Explanation: A concentration cell operates when there are different concentrations of ions on either side of the cell, and the potential difference arises due to this concentration gradient.

24. Which of the following is the correct representation of the Nernst equation?

a) $E = E^o - \frac{RT}{nF} \ln Q$
b) $E = E^o + \frac{RT}{nF} \ln Q$
c) $E = E^o - \frac{nF}{RT} \ln Q$
d) $E = E^o - \frac{nF}{RT} \ln P$

Answer: b) $E = E^o + \frac{RT}{nF} \ln Q$
Explanation: The Nernst equation is used to calculate the cell potential under non-standard conditions. It relates the concentration of reactants and products to the electrode potential.

25. What is the standard electrode potential of a hydrogen electrode?

a) 1.23 V
b) -1.23 V
c) 0 V
d) 2.71 V

Answer: c) 0 V
Explanation: The standard electrode potential of the hydrogen electrode is defined as 0 V at standard conditions (1 M concentration, 1 atm pressure, 298 K).

26. Which of the following is true about a concentration cell?

a) It produces energy by redox reactions.
b) It has equal concentrations of ions on both sides.
c) It has different concentrations of ions on both sides.
d) It requires a salt bridge.

Answer: c) It has different concentrations of ions on both sides.
Explanation: A concentration cell works by creating a potential difference due to the difference in ion concentrations between two half-cells.

27. The cell potential is negative for:

a) A spontaneous reaction
b) A non-spontaneous reaction
c) A concentration cell
d) A galvanic cell

Answer: b) A non-spontaneous reaction
Explanation: A negative cell potential indicates that the reaction is non-spontaneous, as is the case in an electrolytic cell.

28. The relation between cell potential and Gibbs free energy is given by:

a) $\Delta G = nFE_{\text{cell}}$
b) $\Delta G = -nFE_{\text{cell}}$
c) $\Delta G = nF$
d) $\Delta G = \frac{nF}{E_{\text{cell}}}$

Answer: b) $\Delta G = -nFE_{\text{cell}}$
Explanation: The relationship between Gibbs free energy ( $\Delta G$ ) and cell potential ( $E_{\text{cell}}$ ) is $\Delta G = -nFE_{\text{cell}}$ , where $n$ is the number of moles of electrons, and $F$ is Faraday's constant.

29. Which of the following is the standard condition for the Nernst equation?

a) 298 K, 1 atm, 1 M concentration
b) 1 K, 1 atm, 1 M concentration
c) 298 K, 1 atm, 2 M concentration
d) 1 K, 2 atm, 1 M concentration

Answer: a) 298 K, 1 atm, 1 M concentration
Explanation: The Nernst equation assumes standard conditions of 298 K, 1 atm pressure, and 1 M concentration for the substances involved in the reaction.

30. Which of the following does NOT affect the conductivity of a solution?

a) Temperature
b) Ionic concentration
c) Ionic mobility
d) Volume of the solution

Answer: d) Volume of the solution
Explanation: While temperature, ionic concentration, and ionic mobility affect conductivity, the volume of the solution does not have a direct effect on conductivity.

31. In the electrochemical series, a more positive electrode potential indicates:

a) Higher tendency to gain electrons
b) Higher tendency to lose electrons
c) No tendency to change
d) Lower reduction potential

Answer: a) Higher tendency to gain electrons
Explanation: A more positive electrode potential indicates a greater tendency of a substance to gain electrons (reduce).

32. Which of the following processes occurs at the anode during electrolysis?

a) Reduction
b) Oxidation
c) Deposition
d) Dissolution

Answer: b) Oxidation
Explanation: At the anode, oxidation occurs, where electrons are lost.

33. Which of the following is the reducing agent in the reaction: $\text{Cu}^{2+} + 2e^- \rightarrow \text{Cu}$ ?

a) Cu
b) Cu $^{2+}$
c) Electrons
d) None of the above

Answer: b) Cu $^{2+}$
Explanation: In the given reaction, Cu $^{2+}$ is reduced to Cu, meaning Cu $^{2+}$ is the oxidizing agent. The reducing agent is the substance that donates electrons, i.e., electrons here.

34. What is the role of the cathode in an electrolytic cell?

a) It is the site of oxidation
b) It is the site of reduction
c) It supplies electrons to the anode
d) It conducts electricity in the cell

Answer: b) It is the site of reduction
Explanation: In an electrolytic cell, reduction occurs at the cathode, where electrons are gained by cations to form neutral atoms or molecules.

35. Which of the following gases is produced at the cathode during electrolysis of water?

a) Hydrogen gas
b) Oxygen gas
c) Chlorine gas
d) Nitrogen gas

Answer: a) Hydrogen gas
Explanation: During the electrolysis of water, hydrogen gas is produced at the cathode through the reduction of H $^{+}$ ions.

36. What is the main principle of operation of a fuel cell?

a) Oxidation of hydrogen to produce electricity
b) Oxidation of hydrogen to produce heat
c) Reduction of oxygen to produce electricity
d) Both a and c

Answer: d) Both a and c
Explanation: A fuel cell operates by the oxidation of hydrogen at the anode and reduction of oxygen at the cathode, producing electricity and water as a byproduct.

37. Which of the following statements is true about the conductance of electrolytic solutions?

a) It decreases with increasing concentration
b) It increases with increasing concentration
c) It is unaffected by concentration
d) It is only dependent on temperature

Answer: b) It increases with increasing concentration
Explanation: The conductance of an electrolytic solution generally increases with concentration because there are more ions available to conduct electricity.

38. The electrochemical series is based on:

a) Ionization potentials of elements
b) Oxidation potentials of elements
c) Reduction potentials of elements
d) Atomic number of elements

Answer: c) Reduction potentials of elements
Explanation: The electrochemical series is based on the reduction potentials of elements, which indicate their tendency to gain electrons.

39. What is the function of the electrolyte in a galvanic cell?

a) To increase the conductivity of the solution
b) To provide a medium for the flow of ions
c) To increase the rate of reaction
d) To decrease the resistance

Answer: b) To provide a medium for the flow of ions
Explanation: The electrolyte provides a medium for the flow of ions between the two half-cells, allowing the reaction to proceed.

40. Which of the following is a primary source of energy in a fuel cell?

a) Solar energy
b) Hydrogen and oxygen
c) Carbon and oxygen
d) Sodium and chloride

Answer: b) Hydrogen and oxygen
Explanation: In a fuel cell, the primary source of energy is the reaction between hydrogen and oxygen, producing water and electricity.

41. What is the standard electrode potential of a Zn/Zn²⁺ electrode?

a) +0.76 V
b) 0 V
c) -0.76 V
d) +1.23 V

Answer: c) -0.76 V
Explanation: The standard electrode potential of the zinc electrode (Zn/Zn²⁺) is -0.76 V, meaning zinc has a tendency to lose electrons and get oxidized.

42. Which of the following is true for the cathode in an electrolytic cell?

a) It is the site of oxidation
b) It is the site of reduction
c) It is negatively charged
d) Both b and c

Answer: d) Both b and c
Explanation: In an electrolytic cell, the cathode is the site of reduction (where electrons are gained), and it is negatively charged because it attracts positive ions.

43. Which of the following substances will undergo oxidation at the anode in an electrochemical cell?

a) Cl⁻
b) Na⁺
c) Zn
d) H₂O

Answer: c) Zn
Explanation: Zinc (Zn) is oxidized at the anode to Zn²⁺ by losing electrons in an electrochemical cell.

44. The process of electrolysis is used to:

a) Generate electricity
b) Decompose compounds into their elements
c) Increase the concentration of electrolytes
d) Both a and c

Answer: b) Decompose compounds into their elements
Explanation: Electrolysis is the process of using an electric current to decompose a compound into its elements or simpler compounds.

45. Which of the following is the correct equation for the Nernst equation when calculating the cell potential?

a) $E = E^o + \frac{RT}{nF} \ln Q$
b) $E = E^o + \frac{nF}{RT} \ln Q$
c) $E = E^o - \frac{RT}{nF} \ln Q$
d) $E = E^o - \frac{nF}{RT} \ln P$

Answer: a) $E = E^o + \frac{RT}{nF} \ln Q$
Explanation: The Nernst equation is used to calculate the cell potential under non-standard conditions. It accounts for the concentration of reactants and products (Q).

46. In an electrolytic cell, if the substance is more easily reduced than oxidized, it will:

a) Gain electrons at the anode
b) Lose electrons at the anode
c) Gain electrons at the cathode
d) Lose electrons at the cathode

Answer: c) Gain electrons at the cathode
Explanation: In an electrolytic cell, reduction occurs at the cathode, where substances that are more easily reduced will gain electrons.

47. In a galvanic cell, the anode is:

a) Where reduction occurs
b) The positive electrode
c) The negative electrode
d) Where oxidation occurs

Answer: d) Where oxidation occurs
Explanation: In a galvanic cell, oxidation occurs at the anode, which is the source of electrons.

48. Which of the following is the primary purpose of a salt bridge in a galvanic cell?

a) To connect the anode and cathode
b) To maintain electrical neutrality in the cell
c) To increase the voltage of the cell
d) To facilitate the transfer of electrons

Answer: b) To maintain electrical neutrality in the cell
Explanation: The salt bridge helps maintain electrical neutrality by allowing ions to move between the two half-cells, preventing charge buildup.

49. The electrode potential of the standard hydrogen electrode is:

a) +1.00 V
b) -1.00 V
c) 0.00 V
d) 1.23 V

Answer: c) 0.00 V
Explanation: The standard electrode potential of the standard hydrogen electrode (SHE) is defined as 0.00 V at standard conditions (1 M concentration, 1 atm pressure, and 298 K).

50. Which of the following is true for an electrolytic cell?

a) It converts chemical energy into electrical energy
b) It uses electrical energy to drive a non-spontaneous reaction
c) It generates power by spontaneous reactions
d) It operates without an external power source

Answer: b) It uses electrical energy to drive a non-spontaneous reaction
Explanation: An electrolytic cell uses external electrical energy to drive a non-spontaneous reaction, such as in electroplating or the electrolysis of water.

Chapter 3 Electrochemistry

Class 12th Chemistry Chapter MCQs