ELECTROCHEMISTRY CLASS 12 CBSE

Electrochemical Cell

• A device that converts chemical energy into electrical energy.

• Consists of two half-cells:

  • Anode → Oxidation

  • Cathode → Reduction

• Electron flow: Anode → Cathode

• Mnemonic:
  AnOx – RedCat
  (Anode Oxidation, Cathode Reduction)

• Galvanic (Voltaic) Cell

  • Spontaneous redox reaction.

  • Produces electricity.

  • Example: Daniell Cell

  • Zn | Zn²⁺ || Cu²⁺ | Cu

• Electrode Potential (E°)

  • Tendency of an electrode to lose or gain electrons.

  • Measured relative to Standard Hydrogen Electrode (SHE).

  • Unit: Volt (V)

  📌 Standard conditions:

  • Concentration: 1 M

  • Pressure: 1 atm

  • Temperature: 298 K

• Standard Cell Potential (E°cell)

  $$E^\circ_{\text{cell}} = E^\circ_{\text{cathode}} - E^\circ_{\text{anode}}$$

  • If E°cell > 0 → reaction is spontaneous.

• Nernst Equation (VERY IMPORTANT 🔥)

  For a cell reaction:

  $$E = E^\circ - \frac{0.0591}{n} \log Q$$

  Where:

  • n = number of electrons transferred

  • Q = reaction quotient

  At equilibrium:

  $$E = 0$$

Relationship Between ΔG° and E°

$$\Delta G^\circ = -nFE^\circ$$

• If ΔG° < 0 → spontaneous reaction

• Conductance

  • Resistance (R): opposition to current

  • Conductance (G):

  $$G = \frac{1}{R}$$

• Electrolysis

  • Non-spontaneous reaction using electricity.

  • Occurs in electrolytic cell.

  • Anode → Oxidation

  • Cathode → Reduction

• Faraday’s Laws of Electrolysis (VERY IMPORTANT)

  First Law:

  Mass deposited ∝ charge passed

  $$m = ZQ$$

  Second Law:

  Mass deposited ∝ equivalent weight

• Batteries (Short Notes)

  • Dry Cell → Used in torches

  • Lead Storage Battery → Used in cars

  • Fuel Cell → H₂–O₂ cell (eco-friendly)