Chapter 2: Electrochemistry Assertion-Reason Questions | chemistry Class 12 CBSE

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 1

Logic Check

Assertion (A): In a galvanic cell, the electrode at which oxidation takes place is called the anode and has a negative potential. Reason (R): Oxidation involves loss of electrons, which accumulate at the anode, making it negatively charged with respect to the solution.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 2

Logic Check

Assertion (A): The conductivity of an electrolytic solution always decreases with dilution. Reason (R): Dilution decreases the number of ions per unit volume of the solution that carry the current.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 3

Logic Check

Assertion (A): The molar conductivity of a weak electrolyte cannot be determined by extrapolating the Λm vs c½ graph to zero concentration. Reason (R): For weak electrolytes, the Λm vs c½ graph is linear just like for strong electrolytes, but with a steeper slope.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 4

Logic Check

Assertion (A): The standard electrode potential (E°) of the standard hydrogen electrode is taken as zero at all temperatures. Reason (R): This is an arbitrary convention adopted by IUPAC to establish a reference point for measuring electrode potentials of other half-cells.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 5

Logic Check

Assertion (A): Copper does not dissolve in dilute hydrochloric acid. Reason (R): The standard electrode potential of Cu²⁺/Cu (+0.34 V) is positive, indicating that H⁺ ions cannot oxidize copper under standard conditions.

Reasoning Options

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Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 6

Logic Check

Assertion (A): During electrolysis of aqueous NaCl, Cl₂ is produced at the anode rather than O₂, even though E° for water oxidation is lower. Reason (R): Due to the overpotential of oxygen, the oxidation of Cl⁻ ions is kinetically preferred over water oxidation.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 7

Logic Check

Assertion (A): The EMF of a cell is an intensive property and does not depend on the amount of reaction. Reason (R): When the equation for the cell reaction is doubled, the number of electrons (n) transferred doubles, and since ΔrG = −nFE(cell), E(cell) remains unchanged.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 8

Logic Check

Assertion (A): An AC source is used instead of DC for measuring conductivity of ionic solutions. Reason (R): DC current causes electrolysis of the solution, changing its composition and giving erroneous conductivity values.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 9

Logic Check

Assertion (A): A positive value of E°cell always indicates that the cell reaction is spontaneous. Reason (R): ΔrG° = −nFE°cell; a positive E°cell gives negative ΔrG°, confirming spontaneity.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 10

Logic Check

Assertion (A): The molar conductivity of a strong electrolyte increases with decreasing concentration. Reason (R): At lower concentrations, the ionic interactions (inter-ionic attractions) decrease, so ions can migrate more freely and independently.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 11

Logic Check

Assertion (A): In the mercury cell, the cell potential remains constant throughout its operational life. Reason (R): The overall cell reaction in the mercury cell does not involve any ions in solution whose concentration would change during the life of the cell.

Reasoning Options

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Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 12

Logic Check

Assertion (A): Zinc coated iron (galvanized iron) is protected from corrosion even when the zinc coating is scratched and iron is exposed. Reason (R): Zinc has a higher (more positive) standard electrode potential than iron, so zinc gets preferentially oxidized.

Reasoning Options

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Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 13

Logic Check

Assertion (A): Electrolytes of the same type (e.g., all 1-1 electrolytes) have the same Λ°m value. Reason (R): The value of constant A in the Debye-Hückel-Onsager equation depends only on the charges on the cation and anion, not on the specific identities of the ions.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 14

Logic Check

Assertion (A): Faraday's laws of electrolysis indicate that the mass of substance deposited at an electrode is proportional to the quantity of electricity (charge) passed. Reason (R): One Faraday of charge (96487 C) deposits exactly one gram-equivalent of any substance.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 15

Logic Check

Assertion (A): In the Daniell cell, as the cell operates, the voltage decreases over time. Reason (R): As the reaction proceeds, Cu²⁺ concentration decreases and Zn²⁺ concentration increases, and by the Nernst equation, this causes a decrease in E(cell).

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 16

Logic Check

Assertion (A): Platinum and gold are used as inert electrodes in some electrochemical cells. Reason (R): These metals participate actively in the electrode reactions, enhancing the rate of the cell reaction.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 17

Logic Check

Assertion (A): Fuel cells have higher efficiency than thermal power plants. Reason (R): Fuel cells directly convert chemical energy to electrical energy, bypassing intermediate conversions to heat and mechanical energy that cause large energy losses.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 18

Logic Check

Assertion (A): The equilibrium constant (Kc) of an electrochemical cell reaction can be calculated from its E°cell value. Reason (R): At equilibrium, E(cell) = 0, and applying the Nernst equation gives E°cell = (2.303RT/nF) log Kc.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 19

Logic Check

Assertion (A): The conductivity of metallic conductors decreases with increase in temperature. Reason (R): At higher temperatures, increased lattice vibrations in metals hinder the movement of free electrons, increasing resistance.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 20

Logic Check

Assertion (A): The ionic conductance of electrolytic solutions increases with rise in temperature. Reason (R): Higher temperature decreases the viscosity of the solvent and increases the kinetic energy of ions, allowing faster ionic migration.

Reasoning Options

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Chapter sections

Chapter 2: Electrochemistry | Assertion-Reason

Assertion (A): In a galvanic cell, the electrode at which oxidation takes place is called the anode and has a negative potential. Reason (R): Oxidation involves loss of electrons, which accumulate at the anode, making it negatively charged with respect to the solution.

Assertion (A): The conductivity of an electrolytic solution always decreases with dilution. Reason (R): Dilution decreases the number of ions per unit volume of the solution that carry the current.

Assertion (A): The molar conductivity of a weak electrolyte cannot be determined by extrapolating the Λm vs c½ graph to zero concentration. Reason (R): For weak electrolytes, the Λm vs c½ graph is linear just like for strong electrolytes, but with a steeper slope.

Assertion (A): The standard electrode potential (E°) of the standard hydrogen electrode is taken as zero at all temperatures. Reason (R): This is an arbitrary convention adopted by IUPAC to establish a reference point for measuring electrode potentials of other half-cells.

Assertion (A): Copper does not dissolve in dilute hydrochloric acid. Reason (R): The standard electrode potential of Cu²⁺/Cu (+0.34 V) is positive, indicating that H⁺ ions cannot oxidize copper under standard conditions.

Assertion (A): During electrolysis of aqueous NaCl, Cl₂ is produced at the anode rather than O₂, even though E° for water oxidation is lower. Reason (R): Due to the overpotential of oxygen, the oxidation of Cl⁻ ions is kinetically preferred over water oxidation.

Assertion (A): The EMF of a cell is an intensive property and does not depend on the amount of reaction. Reason (R): When the equation for the cell reaction is doubled, the number of electrons (n) transferred doubles, and since ΔrG = −nFE(cell), E(cell) remains unchanged.

Assertion (A): An AC source is used instead of DC for measuring conductivity of ionic solutions. Reason (R): DC current causes electrolysis of the solution, changing its composition and giving erroneous conductivity values.

Assertion (A): A positive value of E°cell always indicates that the cell reaction is spontaneous. Reason (R): ΔrG° = −nFE°cell; a positive E°cell gives negative ΔrG°, confirming spontaneity.

Assertion (A): The molar conductivity of a strong electrolyte increases with decreasing concentration. Reason (R): At lower concentrations, the ionic interactions (inter-ionic attractions) decrease, so ions can migrate more freely and independently.

Assertion (A): In the mercury cell, the cell potential remains constant throughout its operational life. Reason (R): The overall cell reaction in the mercury cell does not involve any ions in solution whose concentration would change during the life of the cell.

Assertion (A): Zinc coated iron (galvanized iron) is protected from corrosion even when the zinc coating is scratched and iron is exposed. Reason (R): Zinc has a higher (more positive) standard electrode potential than iron, so zinc gets preferentially oxidized.

Assertion (A): Electrolytes of the same type (e.g., all 1-1 electrolytes) have the same Λ°m value. Reason (R): The value of constant A in the Debye-Hückel-Onsager equation depends only on the charges on the cation and anion, not on the specific identities of the ions.

Assertion (A): Faraday's laws of electrolysis indicate that the mass of substance deposited at an electrode is proportional to the quantity of electricity (charge) passed. Reason (R): One Faraday of charge (96487 C) deposits exactly one gram-equivalent of any substance.

Assertion (A): In the Daniell cell, as the cell operates, the voltage decreases over time. Reason (R): As the reaction proceeds, Cu²⁺ concentration decreases and Zn²⁺ concentration increases, and by the Nernst equation, this causes a decrease in E(cell).

Assertion (A): Platinum and gold are used as inert electrodes in some electrochemical cells. Reason (R): These metals participate actively in the electrode reactions, enhancing the rate of the cell reaction.

Assertion (A): Fuel cells have higher efficiency than thermal power plants. Reason (R): Fuel cells directly convert chemical energy to electrical energy, bypassing intermediate conversions to heat and mechanical energy that cause large energy losses.

Assertion (A): The equilibrium constant (Kc) of an electrochemical cell reaction can be calculated from its E°cell value. Reason (R): At equilibrium, E(cell) = 0, and applying the Nernst equation gives E°cell = (2.303RT/nF) log Kc.

Assertion (A): The conductivity of metallic conductors decreases with increase in temperature. Reason (R): At higher temperatures, increased lattice vibrations in metals hinder the movement of free electrons, increasing resistance.

Assertion (A): The ionic conductance of electrolytic solutions increases with rise in temperature. Reason (R): Higher temperature decreases the viscosity of the solvent and increases the kinetic energy of ions, allowing faster ionic migration.

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