Important Questions Class 12 Chemistry Chapter 2 Electrochemistry With Answers

Electrochemistry studies how chemical reactions produce electricity and how electricity drives chemical change. It explains galvanic cells, electrolytic cells, batteries, fuel cells, corrosion, conductance, and electrolysis.

Electric current can come from a redox reaction, and the same current can force another reaction to occur. Important Questions Class 12 Chemistry Chapter 2 help students handle this idea through cells, electrode potential, Nernst equation, conductance, electrolysis, batteries, fuel cells, and corrosion. CBSE 2026 questions from Electrochemistry often mix theory with numerical steps, which makes formula clarity important. Students should revise cell notation, sign convention, conductivity units, Faraday calculations, and corrosion reactions with the NCERT Reprint 2026-27 as the final syllabus base.

Key Takeaways

• Electrochemical Cell: A galvanic cell converts chemical energy from a spontaneous redox reaction into electrical energy.
• Nernst Equation: Cell potential changes with ion concentration, temperature, and reaction quotient.
• Conductivity: Conductivity decreases on dilution, while molar conductivity increases on dilution.
• Electrolysis: Faraday’s laws connect the amount of substance deposited with charge passed through the electrolyte.

Important Questions Class 12 Chemistry Chapter 2 Structure 2026

Important Questions Class 12 Chemistry Chapter 2 Electrochemistry Overview

Electrochemistry connects redox reactions with electrical work. This section builds the base for Electrochemistry Class 12 Important Questions before moving to numericals.

Q1. What Is Electrochemistry?

Electrochemistry is the study of electricity produced by chemical reactions and chemical changes produced by electricity. It covers galvanic cells and electrolytic cells.

A galvanic cell produces electricity from a spontaneous redox reaction.

An electrolytic cell uses electricity to carry out a non-spontaneous reaction.

Q2. What Is The Difference Between Galvanic And Electrolytic Cells?

A galvanic cell produces electrical energy, while an electrolytic cell consumes electrical energy. Both involve oxidation and reduction at electrodes.

Q3. How Is Daniell Cell Represented?

Daniell cell is represented as Zn(s) | Zn²⁺(aq) || Cu²⁺(aq) | Cu(s). Zinc acts as anode and copper acts as cathode.

Anode reaction:
Zn(s) → Zn²⁺(aq) + 2e⁻

Cathode reaction:
Cu²⁺(aq) + 2e⁻ → Cu(s)

Overall reaction:
Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)

Electrons flow from zinc to copper through the external circuit.

Electrochemistry Class 12 Important Questions On Cell Potential And Nernst Equation

Cell potential questions are central to Electrochemistry Class 12 important questions with answers. Students must know electrode signs, formula use, and concentration effect.

Q4. What Is Cell Potential?

Cell potential is the potential difference between the two electrodes of a galvanic cell. It is measured in volts.

Formula:
Ecell = Ecathode - Eanode

For standard conditions:
E°cell = E°cathode - E°anode

In Daniell cell:
E°cell = E°Cu²⁺/Cu - E°Zn²⁺/Zn
E°cell = 0.34 V - (-0.76 V)
E°cell = 1.10 V

Final Answer: E°cell = 1.10 V

Q5. What Is Standard Hydrogen Electrode?

Standard hydrogen electrode is the reference electrode with zero electrode potential at all temperatures. It helps measure standard electrode potentials.

Representation:
Pt(s) | H₂(g, 1 bar) | H⁺(aq, 1 M)

Half-cell reaction:
H⁺(aq) + e⁻ → 1/2 H₂(g)

Its assigned electrode potential is 0.00 V.

Q6. How Do You Calculate Standard Cell Potential?

Standard cell potential is calculated by subtracting anode reduction potential from cathode reduction potential.

Formula:
E°cell = E°cathode - E°anode

Example for Zn-Cu cell:

Given:
E°Cu²⁺/Cu = 0.34 V
E°Zn²⁺/Zn = -0.76 V

Calculation:
E°cell = 0.34 V - (-0.76 V)
E°cell = 1.10 V

Final Result: E°cell = 1.10 V

Q7. What Is The Nernst Equation?

Nernst equation gives electrode or cell potential at non-standard concentrations. It shows how concentration changes emf.

For a general cell reaction:
aA + bB → cC + dD

Formula:
Ecell = E°cell - (RT/nF) ln Q

At 298 K:
Ecell = E°cell - (0.0591/n) log Q

For Daniell cell:
Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)

Formula:
Ecell = E°cell - (0.0591/2) log ([Zn²⁺] / [Cu²⁺])

Q8. Calculate Ecell For Mg And Ag Cell

The cell potential is 2.96 V for the given Mg-Ag cell. The Nernst equation is used because concentrations are not standard.

Given Data:
Cell reaction: Mg(s) + 2Ag⁺(0.0001 M) → Mg²⁺(0.130 M) + 2Ag(s)
E°cell = 3.17 V
n = 2
[Mg²⁺] = 0.130 M
[Ag⁺] = 0.0001 M

Formula Used:
Ecell = E°cell - (0.0591/2) log ([Mg²⁺] / [Ag⁺]²)

Calculation:
Ecell = 3.17 - (0.0591/2) log [0.130 / (0.0001)²]
Ecell = 3.17 - 0.21
Ecell = 2.96 V

Final Result: Ecell = 2.96 V

Q9. How Is Equilibrium Constant Related To Ecell?

Equilibrium constant is related to standard cell potential through the Nernst equation at equilibrium. At equilibrium, Ecell becomes zero.

Formula:
E°cell = (2.303 RT/nF) log K

At 298 K:
E°cell = (0.0591/n) log K

For Daniell cell:

Given Data:
E°cell = 1.10 V
n = 2

Calculation:
1.10 = (0.0591/2) log K
log K = (1.10 × 2) / 0.0591
log K = 37.22

Final Result: K ≈ 10³⁷·²²

Q10. How Is Gibbs Energy Related To Cell Potential?

Gibbs energy is related to cell potential by ΔrG = -nFEcell. A positive cell potential gives negative Gibbs energy.

Formula:
ΔrG = -nFEcell

For standard conditions:
ΔrG° = -nFE°cell

For Daniell cell:

Given Data:
n = 2
F = 96487 C mol⁻¹
E°cell = 1.10 V

Calculation:
ΔrG° = -2 × 96487 × 1.10
ΔrG° = -212271.4 J mol⁻¹
ΔrG° = -212.27 kJ mol⁻¹

Final Result: ΔrG° = -212.27 kJ mol⁻¹

Class 12 Chemistry Chapter 2 Questions And Answers On Conductance

Conductance questions test definitions, units, dilution trends, and calculations. This section covers Class 12 Chemistry Chapter 2 questions and answers from conductivity and molar conductivity.

Q11. What Are Resistance, Conductance, Resistivity, And Conductivity?

Resistance opposes current, while conductance measures ease of current flow. Resistivity and conductivity describe material behaviour.

Resistance:
R = ρl/A

Conductance:
G = 1/R

Conductivity:
κ = 1/ρ

Conductance relation:
G = κA/l

Cell constant:
G* = l/A

Conductivity from cell constant:
κ = G*/R

Q12. What Is Molar Conductivity?

Molar conductivity is the conductance of the volume of solution containing one mole of electrolyte. It is denoted by Λm.

Formula:
Λm = κ/c

When κ is in S cm⁻¹ and concentration is in mol L⁻¹:

Formula:
Λm = (κ × 1000) / Molarity

Unit:
S cm² mol⁻¹

Molar conductivity increases on dilution because the volume containing one mole of electrolyte increases.

Q13. How Does Conductivity Change With Dilution?

Conductivity decreases with dilution because ions per unit volume decrease. Fewer ions remain available in one unit volume to carry current.

For strong and weak electrolytes, conductivity decreases on dilution.

Molar conductivity increases on dilution.

For weak electrolytes, molar conductivity rises steeply because degree of dissociation increases strongly.

Q14. What Is Kohlrausch Law?

Kohlrausch law states that limiting molar conductivity equals the sum of individual ionic contributions. It applies at infinite dilution.

For NaCl:
Λ°m(NaCl) = λ°Na⁺ + λ°Cl⁻

General formula:
Λ°m = ν⁺λ°⁺ + ν⁻λ°⁻

Applications:
It helps calculate Λ°m of weak electrolytes.
It helps calculate degree of dissociation.
It helps calculate dissociation constant.
It helps determine limiting molar conductivity.

Q15. Calculate Molar Conductivity From Conductivity

The molar conductivity is 124 S cm² mol⁻¹ for the given KCl solution.

Given Data:
κ = 0.248 × 10⁻² S cm⁻¹
Molarity = 0.02 mol L⁻¹

Formula Used:
Λm = (κ × 1000) / Molarity

Calculation:
Λm = (0.248 × 10⁻² × 1000) / 0.02
Λm = 2.48 / 0.02
Λm = 124 S cm² mol⁻¹

Final Result: Λm = 124 S cm² mol⁻¹

Q16. Calculate Cell Constant From Resistance And Conductivity

The cell constant is calculated by multiplying conductivity with resistance.

Given Data:
Resistance = 100 Ω
Conductivity = 1.29 S m⁻¹

Formula Used:
Cell constant = conductivity × resistance
G* = κ × R

Calculation:
G* = 1.29 × 100
G* = 129 m⁻¹

Conversion:
129 m⁻¹ = 1.29 cm⁻¹

Final Result: Cell constant = 129 m⁻¹ or 1.29 cm⁻¹

Electrochemistry Class 12 Questions With Answers On Electrolysis

Electrolysis questions appear as concept, product prediction, and numerical questions. These Electrochemistry Class 12 questions with answers follow the NCERT reaction logic.

Q17. What Are Faraday’s Laws Of Electrolysis?

Faraday’s laws relate the amount of substance formed during electrolysis to the charge passed. They help calculate deposited mass.

First Law:
Mass deposited is directly proportional to charge passed.

Formula:
Q = It

Second Law:
Masses of different substances liberated by the same charge are proportional to their chemical equivalent weights.

One faraday:
1 F = 96487 C mol⁻¹

Approximate value:
1 F = 96500 C mol⁻¹

Q18. Calculate Copper Deposited During Electrolysis

The mass of copper deposited is 0.2938 g. This is based on charge passed and Cu²⁺ reduction.

Given Data:
Current = 1.5 A
Time = 10 min = 600 s
Molar mass of Cu = 63 g mol⁻¹
n = 2
F = 96487 C mol⁻¹

Formula Used:
Q = It

Mass = (Molar mass × Q) / (nF)

Calculation:
Q = 1.5 × 600
Q = 900 C
Mass = (63 × 900) / (2 × 96487)
Mass = 56700 / 192974
Mass = 0.2938 g

Final Result: Mass of Cu deposited = 0.2938 g

Q19. What Are The Products Of Electrolysis Of Molten NaCl?

Molten NaCl gives sodium metal at cathode and chlorine gas at anode. Only Na⁺ and Cl⁻ ions are present.

Cathode reaction:
Na⁺ + e⁻ → Na

Anode reaction:
Cl⁻ → 1/2 Cl₂ + e⁻

Overall reaction:
NaCl(l) → Na(l) + 1/2 Cl₂(g)

This is an important extraction reaction.

Q20. What Are The Products Of Electrolysis Of Aqueous NaCl?

Aqueous NaCl gives hydrogen gas, chlorine gas, and sodium hydroxide. Water also participates in the electrode reactions.

At cathode:
H₂O(l) + e⁻ → 1/2 H₂(g) + OH⁻(aq)

At anode:
Cl⁻(aq) → 1/2 Cl₂(g) + e⁻

Overall reaction:
NaCl(aq) + H₂O(l) → Na⁺(aq) + OH⁻(aq) + 1/2 H₂(g) + 1/2 Cl₂(g)

Final products: NaOH, H₂, and Cl₂

Q21. Why Do Products Of Electrolysis Depend On Electrodes?

Products of electrolysis depend on whether the electrode is inert or reactive. Inert electrodes only transfer electrons, while reactive electrodes can take part in reactions.

Platinum and gold usually act as inert electrodes.

Copper can act as a reactive electrode.

Products also depend on electrode potential, concentration, and overpotential.

In aqueous NaCl, chlorine forms at the anode due to oxygen overpotential.

Electrochemistry Class 12 Important Questions On Batteries And Fuel Cells

Batteries and fuel cells are practical forms of galvanic cells. These questions connect Electrochemistry Class 12 numericals and concepts with real devices.

Q22. What Is A Primary Battery?

A primary battery cannot be recharged after use. Its reaction occurs only once.

Example: dry cell or Leclanche cell.

Dry cell structure:
Zinc container acts as anode.
Carbon rod acts as cathode.
Moist paste of NH₄Cl and ZnCl₂ acts as electrolyte.
MnO₂ and carbon surround the cathode.

Approximate cell potential: 1.5 V

Q23. What Is A Secondary Battery?

A secondary battery can be recharged by passing current in the opposite direction. It can undergo many charging and discharging cycles.

Example: lead storage battery.

During discharge:

Anode reaction:
Pb(s) + SO₄²⁻(aq) → PbSO₄(s) + 2e⁻

Cathode reaction:
PbO₂(s) + SO₄²⁻(aq) + 4H⁺(aq) + 2e⁻ → PbSO₄(s) + 2H₂O(l)

Overall reaction:
Pb(s) + PbO₂(s) + 2H₂SO₄(aq) → 2PbSO₄(s) + 2H₂O(l)

During charging, the reaction reverses.

Q24. What Is A Fuel Cell?

A fuel cell is a galvanic cell that converts fuel energy directly into electrical energy. Reactants enter continuously, and products leave continuously.

Hydrogen-oxygen fuel cell:

Cathode reaction:
O₂(g) + 2H₂O(l) + 4e⁻ → 4OH⁻(aq)

Anode reaction:
2H₂(g) + 4OH⁻(aq) → 4H₂O(l) + 4e⁻

Overall reaction:
2H₂(g) + O₂(g) → 2H₂O(l)

The product is water.

Q25. Why Are Fuel Cells More Efficient Than Thermal Plants?

Fuel cells are more efficient because they directly convert chemical energy into electrical energy. Thermal plants first convert chemical energy into heat.

Fuel cell efficiency is about 70%.

Thermal plant efficiency is about 40%.

Fuel cells also reduce pollution when clean fuels like hydrogen are used.

Class 12 Electrochemistry Important Questions On Corrosion

Corrosion is an electrochemical process involving oxidation and reduction. This section covers corrosion Class 12 Chemistry with direct board-style answers.

Q26. Why Is Corrosion Electrochemical?

Corrosion is electrochemical because oxidation and reduction occur at different spots on the metal surface. Iron rusting occurs in the presence of air and water.

At anode:
Fe(s) → Fe²⁺(aq) + 2e⁻

At cathode:
O₂(g) + 4H⁺(aq) + 4e⁻ → 2H₂O(l)

Overall reaction:
2Fe(s) + O₂(g) + 4H⁺(aq) → 2Fe²⁺(aq) + 2H₂O(l)

Further oxidation forms hydrated ferric oxide:
Fe₂O₃·xH₂O

This hydrated ferric oxide is rust.

Q27. How Can Corrosion Be Prevented?

Corrosion can be prevented by stopping metal contact with air and moisture. It can also be prevented by using a sacrificial metal.

Methods:
Painting the metal surface.
Applying oil or grease.
Coating with tin or zinc.
Galvanisation with zinc.
Using sacrificial electrodes like Mg or Zn.

Sacrificial metal corrodes first and protects the main metal object.

Q28. Why Can Copper Sulphate Not Be Stored In A Zinc Pot?

Copper sulphate cannot be stored in a zinc pot because zinc displaces copper from CuSO₄ solution. Zinc is a stronger reducing agent than copper.

Reaction:
Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)

Zinc oxidises to Zn²⁺.

Copper ions reduce to copper metal.

The zinc pot will corrode and get damaged.

Q29. Which Metals Are Strong Reducing Agents?

Metals with highly negative standard electrode potentials are strong reducing agents. They lose electrons easily.

Reducing power increases as standard reduction potential becomes more negative.

From the NCERT table:
Lithium has E° = -3.05 V
Potassium has E° = -2.93 V
Calcium has E° = -2.87 V
Sodium has E° = -2.71 V
Magnesium has E° = -2.36 V

Lithium is the strongest reducing agent among the listed metals in aqueous solution.

Q30. What Are The Most Repeated Electrochemistry Numericals?

The most repeated Electrochemistry numericals come from Nernst equation, Gibbs energy, conductivity, molar conductivity, and Faraday’s laws. These topics combine formulas with clear substitutions.

Most repeated formula lines:

Cell potential:
E°cell = E°cathode - E°anode

Nernst equation at 298 K:
Ecell = E°cell - (0.0591/n) log Q

Gibbs energy:
ΔrG° = -nFE°cell

Equilibrium constant:
E°cell = (0.0591/n) log K

Conductivity:
κ = Cell constant / Resistance

Molar conductivity:
Λm = (κ × 1000) / Molarity

Charge passed:
Q = It

Mass deposited:
Mass = (Molar mass × Q) / (nF)

Class 12 Chemistry Important Links