Introduction to Electrochemistry Class 12 Chemistry

Electrochemistry is the branch of chemistry that deals with the relationship between electrical energy and chemical changes. It primarily involves redox reactions, where oxidation and reduction occur simultaneously. Here are the key concepts and principles of electrochemistry for Class 12 and JEE preparation.

1. Electrochemical Cells

Galvanic (Voltaic) Cells: Convert chemical energy into electrical energy.

Consists of two half-cells connected by a salt bridge.

Anode (oxidation): Zn → Zn²⁺ + 2e⁻

Cathode (reduction): Cu²⁺ + 2e⁻ → Cu

Electrolytic Cells: Use electrical energy to drive non-spontaneous chemical reactions.

3. Electrode Potential

Standard Electrode Potential (E°): Measured under standard conditions (298K, 1M, 1 atm).

Nernst Equation: Used to calculate the cell potential under non-standard conditions.

Ecell​ =E°cathode​−E°anode​

Cell Potential (Ecell): Difference in potential between the cathode and anode.

    Ecell = E°cathode - E°anode

4. Gibbs Free Energy and Cell Potential

ΔG = -nFEcell

If Ecell > 0, the reaction is spontaneous ΔG < 0.

If Ecell< 0, the reaction is non-spontaneous ΔG > 0.

Read Also: Class 11 Notes on Equilibrium in Physical Processes

5. Electrochemical Series

A list of standard electrode potentials.

Metals with higher reduction potential are good oxidizing agents.

Metals with lower reduction potential are good reducing agents.

6. Conductance of Electrolytic Solutions

Conductivity (κ): Measure of the solution’s ability to conduct electricity.

κ=1​/ρ

Molar Conductivity (Λm): Conductivity per unit concentration.

 Λm​= κ​/c

Variation of conductivity with concentration:

Increases with dilution for strong electrolytes.

Initially increases then decreases for weak electrolytes.

7. Kohlrausch's Law of Independent Migration of Ions

The limiting molar conductivity of an electrolyte can be represented as the sum of the individual contributions of the anion and cation.

Λm°​= λ+°​ + λ−°​

8. Electrolysis

Faraday’s Laws of Electrolysis:

First Law: The mass of the substance deposited or liberated is directly proportional to the quantity of electricity passed.

m=Z⋅Q

Second Law: The masses of different substances deposited or liberated by the same quantity of electricity are proportional to their equivalent weights.

9. Batteries and Fuel Cells

Primary Batteries: Non-rechargeable (e.g., dry cell, mercury cell).

Secondary Batteries: Rechargeable (e.g., lead-acid battery, nickel-cadmium battery).

Fuel Cells: Convert chemical energy directly into electrical energy (e.g., hydrogen-oxygen fuel cell).

10. Corrosion

Electrochemical process where metals are oxidized in the presence of air and moisture.

Prevention methods:

Coating (painting, galvanizing).

Using sacrificial anodes.

Applying corrosion inhibitors.

Recommended Books and Resources

1. NCERT Chemistry Class 12 Textbook

2. O.P. Tandon – Physical Chemistry

3. P. Bahadur – Numerical Chemistry

4. JEE Main and Advanced previous years' question papers