Class 12 chemistry MCQs with correct option and explanation. These MCQs are based on the CBSE board Class 12 chemistry syllabus. with the help of these Multiple choice questions, students will be able to quickly review topics covered and prepare for the Class 12 board exam as well as other entrance exams such as NEET and JEE.
Class 12 Electrochemistry MCQs
Q.1: Which of the following is not a conductor of electricity?
(a) Copper
(b) Silver
(c) Pure water
(d) Graphite
(b) Silver
(c) Pure water
(d) Graphite
Answer: (c) Pure water
Explanation: Pure water lacks free ions, so it conducts very poorly.
Explanation: Pure water lacks free ions, so it conducts very poorly.
Q.2: In a galvanic cell, the anode is the electrode where:
(a) Reduction takes place
(b) Oxidation takes place
(c) Electrons are gained
(d) None of the above
(b) Oxidation takes place
(c) Electrons are gained
(d) None of the above
Answer: (b) Oxidation takes place
Explanation: In galvanic cells, oxidation occurs at the anode.
Explanation: In galvanic cells, oxidation occurs at the anode.
Q.3: The standard reduction potential of a half-cell is measured under:
(a) 1 atm pressure
(b) 298 K temperature
(c) 1 M concentration
(d) All of the above
(b) 298 K temperature
(c) 1 M concentration
(d) All of the above
Answer: (d) All of the above
Explanation: Standard conditions are 1 atm, 298 K, and 1 M solutions.
Explanation: Standard conditions are 1 atm, 298 K, and 1 M solutions.
Q.4: The unit of cell constant is:
(a) S cm
(b) cm−1
(c) ohm cm
(d) ohm cm−1
(b) cm−1
(c) ohm cm
(d) ohm cm−1
Answer: (b) cm−1
Explanation: Cell constant = distance/area; unit cm−1.
Explanation: Cell constant = distance/area; unit cm−1.
Q.5: Which of the following statements is true for a galvanic cell?
(a) Anode is positively charged
(b) Cathode is negatively charged
(c) Anode is negatively charged
(d) Electrons flow from cathode to anode
(b) Cathode is negatively charged
(c) Anode is negatively charged
(d) Electrons flow from cathode to anode
Answer: (c) Anode is negatively charged
Explanation: In galvanic cells, anode is the site of oxidation and is negative.
Explanation: In galvanic cells, anode is the site of oxidation and is negative.
Q.6: The molar conductivity of a solution:
(a) Increases with dilution
(b) Decreases with dilution
(c) Remains constant
(d) None of the above
(b) Decreases with dilution
(c) Remains constant
(d) None of the above
Answer: (a) Increases with dilution
Explanation: Dilution increases ion mobility, so molar conductivity rises.
Explanation: Dilution increases ion mobility, so molar conductivity rises.
Q.7: The electrochemical equivalent of a substance is:
(a) Directly proportional to molar mass
(b) Inversely proportional to molar mass
(c) Directly proportional to equivalent mass
(d) Inversely proportional to equivalent mass
(b) Inversely proportional to molar mass
(c) Directly proportional to equivalent mass
(d) Inversely proportional to equivalent mass
Answer: (c) Directly proportional to equivalent mass
Explanation: Electrochemical equivalent ∝ equivalent mass.
Explanation: Electrochemical equivalent ∝ equivalent mass.
Q.8: Faraday's first law of electrolysis states that:
(a) Mass ∝ Current
(b) Mass ∝ Charge
(c) Mass ∝ Time
(d) None of the above
(b) Mass ∝ Charge
(c) Mass ∝ Time
(d) None of the above
Answer: (b) Mass ∝ Charge
Explanation: Mass deposited is proportional to electricity passed.
Explanation: Mass deposited is proportional to electricity passed.
Q.9: The Nernst equation for the cell potential is:
(a) E = E° − (0.059/n) log Q
(b) E = E° + (0.059/n) log Q
(c) E = E° − (RT/nF) ln Q
(d) E = E° + (RT/nF) ln Q
(b) E = E° + (0.059/n) log Q
(c) E = E° − (RT/nF) ln Q
(d) E = E° + (RT/nF) ln Q
Answer: (c) E = E° − (RT/nF) ln Q
Explanation: Nernst equation gives cell potential under non-standard conditions.
Explanation: Nernst equation gives cell potential under non-standard conditions.
Q.10: In the electrolysis of aqueous NaCl, the product at the cathode is:
(a) Cl2
(b) H2
(c) Na
(d) O2
(b) H2
(c) Na
(d) O2
Answer: (b) H2
Explanation: Hydrogen gas is liberated at the cathode.
Explanation: Hydrogen gas is liberated at the cathode.
Q.11: The electrolysis of molten NaCl produces:
(a) Na at cathode and Cl2 at anode
(b) Na at anode and Cl2 at cathode
(c) H2 at cathode and O2 at anode
(d) H2 at anode and O2 at cathode
(b) Na at anode and Cl2 at cathode
(c) H2 at cathode and O2 at anode
(d) H2 at anode and O2 at cathode
Answer: (a) Na at cathode and Cl2 at anode
Explanation: Molten NaCl yields Na metal and Cl2 gas.
Explanation: Molten NaCl yields Na metal and Cl2 gas.
Q.12: Which metal cannot be obtained by electrolysis of its aqueous salt solution?
(a) Cu
(b) Zn
(c) Na
(d) Ag
(b) Zn
(c) Na
(d) Ag
Answer: (c) Na
Explanation: Sodium reacts with water; not obtained from aqueous solution.
Explanation: Sodium reacts with water; not obtained from aqueous solution.
Q.13: The standard electrode potential of Zn2+/Zn is −0.76 V. This means:
(a) Zinc is a strong oxidizing agent
(b) Zinc is a strong reducing agent
(c) Zinc cannot be oxidized
(d) Zinc has low tendency to get reduced
(b) Zinc is a strong reducing agent
(c) Zinc cannot be oxidized
(d) Zinc has low tendency to get reduced
Answer: (b) Zinc is a strong reducing agent
Explanation: Negative E° indicates strong reducing nature.
Explanation: Negative E° indicates strong reducing nature.
Q.14: Product at anode during electrolysis of dilute H2SO4 is:
(a) H2
(b) O2
(c) SO2
(d) H2SO4
(b) O2
(c) SO2
(d) H2SO4
Answer: (b) O2
Explanation: Oxygen gas evolves at the anode.
Explanation: Oxygen gas evolves at the anode.
Q.15: Conductance of a solution is inversely proportional to:
(a) Resistance
(b) Specific conductance
(c) Cell constant
(d) Equivalent conductance
(b) Specific conductance
(c) Cell constant
(d) Equivalent conductance
Answer: (a) Resistance
Explanation: Conductance = 1 / Resistance.
Explanation: Conductance = 1 / Resistance.
Q.16: Which of the following is a primary cell?
(a) Lead-acid battery
(b) Nickel-cadmium battery
(c) Dry cell
(d) Lithium-ion battery
(b) Nickel-cadmium battery
(c) Dry cell
(d) Lithium-ion battery
Answer: (c) Dry cell
Explanation: Primary cells are non-rechargeable.
Explanation: Primary cells are non-rechargeable.
Q.17: The amount of electricity required to deposit 1 mole of a substance is:
(a) 1 Faraday
(b) 1 Coulomb
(c) 96500 Coulombs
(d) 96500 Faradays
(b) 1 Coulomb
(c) 96500 Coulombs
(d) 96500 Faradays
Answer: (c) 96500 Coulombs
Explanation: 1 Faraday = 96500 C.
Explanation: 1 Faraday = 96500 C.
Q.18: The electrode where reduction occurs is called:
(a) Anode
(b) Cathode
(c) Electrolyte
(d) None of the above
(b) Cathode
(c) Electrolyte
(d) None of the above
Answer: (b) Cathode
Explanation: Reduction occurs at the cathode.
Explanation: Reduction occurs at the cathode.
Q.19: The salt bridge in an electrochemical cell is used to:
(a) Complete the circuit
(b) Prevent mixing of solutions
(c) Maintain electrical neutrality
(d) All of the above
(b) Prevent mixing of solutions
(c) Maintain electrical neutrality
(d) All of the above
Answer: (d) All of the above
Explanation: Salt bridge maintains charge balance and completes the circuit.
Explanation: Salt bridge maintains charge balance and completes the circuit.
Q.20: Which of the following statements is true about electrolysis?
(a) It involves the transfer of electrons
(b) It involves the transfer of ions
(c) It is a spontaneous process
(d) None of the above
(b) It involves the transfer of ions
(c) It is a spontaneous process
(d) None of the above
Answer: (a) It involves the transfer of electrons
Explanation: Electron transfer drives redox changes during electrolysis.
Explanation: Electron transfer drives redox changes during electrolysis.
Q.21: In the electrolysis of aqueous CuSO4 using copper electrodes, the mass of the anode:
(a) Increases
(b) Decreases
(c) Remains the same
(d) None of the above
(b) Decreases
(c) Remains the same
(d) None of the above
Answer: (b) Decreases
Explanation: Copper dissolves as Cu2+ at the anode.
Explanation: Copper dissolves as Cu2+ at the anode.
Q.22: The electrode potential of a half-cell depends on:
(a) Temperature
(b) Concentration of ions
(c) Nature of the electrode
(d) All of the above
(b) Concentration of ions
(c) Nature of the electrode
(d) All of the above
Answer: (d) All of the above
Explanation: All listed factors affect electrode potential.
Explanation: All listed factors affect electrode potential.
Q.23: The standard hydrogen electrode is assigned a potential of:
(a) 0.00 V
(b) 1.00 V
(c) 0.059 V
(d) −0.059 V
(b) 1.00 V
(c) 0.059 V
(d) −0.059 V
Answer: (a) 0.00 V
Explanation: By convention, SHE is 0.00 V.
Explanation: By convention, SHE is 0.00 V.
Q.24: During electrolysis of water, the volume of hydrogen collected at the cathode is:
(a) Equal to oxygen
(b) Half of oxygen
(c) Twice oxygen
(d) None of the above
(b) Half of oxygen
(c) Twice oxygen
(d) None of the above
Answer: (c) Twice oxygen
Explanation: H2:O2 = 2:1.
Explanation: H2:O2 = 2:1.
Q.25: The electrochemical series is useful for predicting:
(a) Cell potential
(b) Direction of electron flow
(c) Feasibility of redox reactions
(d) All of the above
(b) Direction of electron flow
(c) Feasibility of redox reactions
(d) All of the above
Answer: (d) All of the above
Explanation: The series helps predict all these.
Explanation: The series helps predict all these.
Q.26: In a concentration cell, the electrode with higher concentration acts as:
(a) Anode
(b) Cathode
(c) Electrolyte
(d) None of the above
(b) Cathode
(c) Electrolyte
(d) None of the above
Answer: (b) Cathode
Explanation: Higher concentration side acts as cathode.
Explanation: Higher concentration side acts as cathode.
Q.27: The pH of a solution can be determined using:
(a) Hydrogen electrode
(b) Glass electrode
(c) Calomel electrode
(d) All of the above
(b) Glass electrode
(c) Calomel electrode
(d) All of the above
Answer: (b) Glass electrode
Explanation: Glass electrodes are standard for pH measurement.
Explanation: Glass electrodes are standard for pH measurement.
Q.28: The equivalent conductance of a strong electrolyte:
(a) Increases with dilution
(b) Decreases with dilution
(c) Remains constant
(d) None of the above
(b) Decreases with dilution
(c) Remains constant
(d) None of the above
Answer: (a) Increases with dilution
Explanation: More complete dissociation and mobility at lower concentration.
Explanation: More complete dissociation and mobility at lower concentration.
Q.29: The emf of a cell can be measured using:
(a) Voltmeter
(b) Ammeter
(c) Potentiometer
(d) Galvanometer
(b) Ammeter
(c) Potentiometer
(d) Galvanometer
Answer: (c) Potentiometer
Explanation: Potentiometers allow precise emf measurement.
Explanation: Potentiometers allow precise emf measurement.
Q.30: The spontaneous reaction in a galvanic cell occurs because:
(a) ΔG is positive
(b) ΔG is negative
(c) ΔH is positive
(d) ΔH is negative
(b) ΔG is negative
(c) ΔH is positive
(d) ΔH is negative
Answer: (b) ΔG is negative
Explanation: Negative Gibbs free energy implies spontaneity.
Explanation: Negative Gibbs free energy implies spontaneity.
Q.31: In an electrolytic cell, the direction of electron flow is:
(a) From anode to cathode
(b) From cathode to anode
(c) Depends on the electrolyte
(d) Depends on the applied voltage
(b) From cathode to anode
(c) Depends on the electrolyte
(d) Depends on the applied voltage
Answer: (b) From cathode to anode
Explanation: Electrons move from the negative cathode to the positive anode (external circuit).
Explanation: Electrons move from the negative cathode to the positive anode (external circuit).
Q.32: In the Nernst equation, E = E° − (RT/nF) ln Q, Q represents:
(a) Reaction quotient
(b) Heat evolved
(c) Concentration of reactants
(d) Number of electrons
(b) Heat evolved
(c) Concentration of reactants
(d) Number of electrons
Answer: (a) Reaction quotient
Explanation: Q = ratio of activities/products to reactants.
Explanation: Q = ratio of activities/products to reactants.
Q.33: The standard cell potential (E°cell) is calculated using:
(a) E°cell = E°cathode + E°anode
(b) E°cell = E°cathode − E°anode
(c) E°cell = E°anode − E°cathode
(d) E°cell = E°anode + E°cathode
(b) E°cell = E°cathode − E°anode
(c) E°cell = E°anode − E°cathode
(d) E°cell = E°anode + E°cathode
Answer: (b) E°cell = E°cathode − E°anode
Explanation: Cell potential = cathode (reduction) − anode (reduction).
Explanation: Cell potential = cathode (reduction) − anode (reduction).
Q.34: A Faraday is equal to:
(a) 1 Coulomb
(b) 96500 Coulombs
(c) 1 mole of electrons
(d) Both (b) and (c)
(b) 96500 Coulombs
(c) 1 mole of electrons
(d) Both (b) and (c)
Answer: (d) Both (b) and (c)
Explanation: 1 F = 96500 C = 1 mol e−.
Explanation: 1 F = 96500 C = 1 mol e−.
Q.35: During electrolysis, the amount of substance deposited is proportional to:
(a) Current
(b) Time
(c) Both (a) and (b)
(d) Voltage
(b) Time
(c) Both (a) and (b)
(d) Voltage
Answer: (c) Both (a) and (b)
Explanation: Faraday’s laws: mass ∝ It.
Explanation: Faraday’s laws: mass ∝ It.
Q.36: The role of a salt bridge in a galvanic cell is to:
(a) Transfer electrons
(b) Complete the circuit
(c) Measure emf
(d) Provide ions for the reaction
(b) Complete the circuit
(c) Measure emf
(d) Provide ions for the reaction
Answer: (b) Complete the circuit
Explanation: It allows ion flow to maintain neutrality.
Explanation: It allows ion flow to maintain neutrality.
Q.37: Which of the following is not a standard condition for measuring electrode potentials?
(a) 1 M concentration
(b) 298 K temperature
(c) 1 atm pressure
(d) 25°C temperature
(b) 298 K temperature
(c) 1 atm pressure
(d) 25°C temperature
Answer: (d) 25°C temperature
Explanation: Conventionally written as 298 K (numerically 25°C), but standard notation uses 298 K.
Explanation: Conventionally written as 298 K (numerically 25°C), but standard notation uses 298 K.
Q.38: The oxidation number of chlorine in NaClO3 is:
(a) +1
(b) +3
(c) +5
(d) +7
(b) +3
(c) +5
(d) +7
Answer: (c) +5
Explanation: Na = +1, O = −2 ×3 = −6; so Cl = +5.
Explanation: Na = +1, O = −2 ×3 = −6; so Cl = +5.
Q.39: The electrolysis of an aqueous solution of KCl produces:
(a) K at cathode and Cl2 at anode
(b) H2 at cathode and Cl2 at anode
(c) K at cathode and O2 at anode
(d) H2 at cathode and O2 at anode
(b) H2 at cathode and Cl2 at anode
(c) K at cathode and O2 at anode
(d) H2 at cathode and O2 at anode
Answer: (b) H2 at cathode and Cl2 at anode
Explanation: Water reduces to H2; chloride oxidizes to Cl2.
Explanation: Water reduces to H2; chloride oxidizes to Cl2.
Q.40: In the context of galvanic cells, EMF stands for:
(a) Electromagnetic Field
(b) Electromotive Force
(c) Electrostatic Force
(d) Electrolytic Mobility
(b) Electromotive Force
(c) Electrostatic Force
(d) Electrolytic Mobility
Answer: (b) Electromotive Force
Explanation: EMF is the potential difference of the cell.
Explanation: EMF is the potential difference of the cell.
Q.41: The conductivity of an electrolyte depends on:
(a) Nature of the electrolyte
(b) Concentration of the electrolyte
(c) Temperature
(d) All of the above
(b) Concentration of the electrolyte
(c) Temperature
(d) All of the above
Answer: (d) All of the above
Explanation: All listed factors influence conductivity.
Explanation: All listed factors influence conductivity.
Q.42: The product formed at the cathode during electrolysis of molten MgCl2 is:
(a) Mg
(b) Cl2
(c) H2
(d) O2
(b) Cl2
(c) H2
(d) O2
Answer: (a) Mg
Explanation: Mg2+ gains electrons to form Mg metal.
Explanation: Mg2+ gains electrons to form Mg metal.
Q.43: For a galvanic cell under standard conditions:
(a) ΔG = 0
(b) ΔG > 0
(c) ΔG < 0
(d) ΔG is independent of the reaction
(b) ΔG > 0
(c) ΔG < 0
(d) ΔG is independent of the reaction
Answer: (c) ΔG < 0
Explanation: Negative ΔG indicates a spontaneous cell reaction.
Explanation: Negative ΔG indicates a spontaneous cell reaction.
Q.44: Which metal is used as a reference electrode?
(a) Zinc
(b) Copper
(c) Platinum
(d) Silver
(b) Copper
(c) Platinum
(d) Silver
Answer: (c) Platinum
Explanation: The standard hydrogen electrode uses Pt.
Explanation: The standard hydrogen electrode uses Pt.
Q.45: The relationship between Gibbs free energy and EMF of a cell is:
(a) ΔG = −nFE
(b) ΔG = nFE
(c) ΔG = nF/E
(d) ΔG = −E/nF
(b) ΔG = nFE
(c) ΔG = nF/E
(d) ΔG = −E/nF
Answer: (a) ΔG = −nFE
Explanation: Links spontaneity (ΔG) to cell EMF.
Explanation: Links spontaneity (ΔG) to cell EMF.
Q.46: In electroplating, the object to be plated is made the:
(a) Anode
(b) Cathode
(c) Electrolyte
(d) None of the above
(b) Cathode
(c) Electrolyte
(d) None of the above
Answer: (b) Cathode
Explanation: Metal ions reduce onto the object at the cathode.
Explanation: Metal ions reduce onto the object at the cathode.
Q.47: The unit of molar conductivity is:
(a) S cm
(b) S cm2 mol−1
(c) S cm mol−1
(d) S cm−1 mol
(b) S cm2 mol−1
(c) S cm mol−1
(d) S cm−1 mol
Answer: (b) S cm2 mol−1
Explanation: Siemens·cm2 per mole.
Explanation: Siemens·cm2 per mole.
Q.48: The corrosion of iron is an electrochemical process involving:
(a) Oxidation of iron at the anode
(b) Reduction of oxygen at the cathode
(c) Both (a) and (b)
(d) None of the above
(b) Reduction of oxygen at the cathode
(c) Both (a) and (b)
(d) None of the above
Answer: (c) Both (a) and (b)
Explanation: Fe oxidizes; O2 reduces, forming rust products.
Explanation: Fe oxidizes; O2 reduces, forming rust products.
Q.49: Which electrolyte is commonly used in a dry cell battery?
(a) NaCl
(b) KOH
(c) NH4Cl
(d) H2SO4
(b) KOH
(c) NH4Cl
(d) H2SO4
Answer: (c) NH4Cl
Explanation: Ammonium chloride is used in Leclanché dry cells.
Explanation: Ammonium chloride is used in Leclanché dry cells.
Q.50: The electrochemical equivalent of a substance is:
(a) Its equivalent weight divided by Faraday's constant
(b) Its molecular weight divided by Faraday's constant
(c) Its atomic weight divided by Faraday's constant
(d) Its valence divided by Faraday's constant
(b) Its molecular weight divided by Faraday's constant
(c) Its atomic weight divided by Faraday's constant
(d) Its valence divided by Faraday's constant
Answer: (a) Equivalent weight / Faraday's constant
Explanation: By definition: Z = Eq. wt. / F.
Explanation: By definition: Z = Eq. wt. / F.