Electrochemistry – Complete Formula Sheet Revision Capsule

 

Electrochemistry – Complete Formula Sheet (JEE Main Only)

1. Electrochemical (Galvanic) Cell

• Oxidation → Anode (−)
• Reduction → Cathode (+)
• Electron flow: Anode → Cathode

Cell Representation:

Anode | Anode electrolyte || Cathode electrolyte | Cathode
Zn | Zn²⁺ || Cu²⁺ | Cu

2. Electrode Potential & Electrochemical Series

Standard Hydrogen Electrode (SHE):

H⁺(1M) | H₂(1 atm) | Pt(s)
E° = 0 V

• More +ve SRP → Strong oxidising agent
• More −ve SRP → Strong reducing agent
• Low SRP metals → Highly reactive

3. EMF of a Cell

Formula:

E°_cell = E°_cathode − E°_anode

E_cell = RP_cathode + OP_anode

Spontaneity:

• E°_cell > 0 → Spontaneous
• E°_cell < 0 → Non-spontaneous

4. Nernst Equation

E_cell = E°_cell − (0.0591 / n) log Q

Example:

Zn | Zn²⁺ || Cu²⁺ | Cu

E_cell = E°_cell − (0.0591 / 2) log ([Zn²⁺]/[Cu²⁺])

5. Relation between EMF, ΔG & Kc

ΔG° = −nF E°_cell

E°_cell = (0.0591 / n) log K_c

Condition	Inference
ΔG° < 0	Spontaneous
Kc > 1	Forward reaction
E°cell > 0	Feasible cell

6. Electrolytic Cell

• Anode → Positive
• Cathode → Negative
• Cations → Cathode
• Anions → Anode

7. Faraday’s Laws of Electrolysis

m = (E × I × t) / 96500

Equivalent mass (E) = Molar mass / Valency

1 Faraday: 1F = 96500 C

• Na⁺ → 1F
• Mg²⁺ → 2F
• Al³⁺ → 3F

8. Products of Electrolysis

Discharge order of cations:

Li⁺ < K⁺ < Ca²⁺ < Na⁺ < Mg²⁺ < Al³⁺ < Zn²⁺ < Fe²⁺ < Ni²⁺ < Cu²⁺ < Ag⁺ < Au³⁺

Discharge order of anions:

SO₄²⁻ < NO₃⁻ < OH⁻ < Cl⁻ < Br⁻ < I⁻

9. Conductance & Conductivity

R = ρl / A
κ = 1 / ρ

Λ_m = (1000 κ) / M

• Strong electrolyte → slight increase on dilution
• Weak electrolyte → sharp increase on dilution

10. Kohlrausch’s Law

Λ°_m = λ°₊ + λ°₋

Applications:

• Λ° of weak electrolyte
• Degree of dissociation
• Ionic mobility comparison

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