Electrochemistry for NEET UG
Electrochemistry links chemical reactions with electricity. It explains batteries, corrosion, electroplating and how we measure the strength of oxidising and reducing agents.
ChemistryClass 1275 MCQs3 lessons14 flashcards3 memory tricks
Practise Electrochemistry free
What you'll learn
- Galvanic cells and electrode potentials
Find the EMF of a cell from standard electrode potentials and write the cell notation. - The Nernst equation
Calculate electrode and cell potentials at non-standard concentrations. - Conductance and electrolysis
Use molar conductivity, Kohlrausch's law and Faraday's laws of electrolysis.
Key formulas
| Cell EMF | E°cell = E°cathode − E°anode (both as reduction potentials) |
|---|---|
| Spontaneous | E°cell > 0 |
| Link to Gibbs energy | ΔG° = −nFE°cell, F = 96,500 C/mol |
| Nernst equation (25 °C) | E = E° − (0.0591/n) log Q |
| At equilibrium | E = 0, so E° = (0.0591/n) log K |
| Conductivity | κ = (1/R)(l/A) |
| Molar conductivity | Λm = κ × 1000/C (S cm² mol⁻¹) |
| Kohlrausch's law | Λ°m = ν₊λ°₊ + ν₋λ°₋ |
Memory tricks
Oxidation at the Anode, Reduction at the Cathode, in every kind of cell.
Higher standard reduction potential means a stronger oxidising agent: F₂ (+2.87 V). Most negative means the strongest reducing agent: Li (−3.04 V).
Salty, humid air is a better electrolyte, so corrosion is faster. Zinc is more reactive than iron, so it corrodes first (sacrificial protection).
Try 3 NEET-style questions
Q1. The charge required to deposit 1 mol of copper from Cu²⁺ solution is
- 1 F
- 2 F
- 3 F
- 0.5 F
Show answer
Answer: (2) 2 F
Cu²⁺ + 2e⁻ → Cu, so 2 mol of electrons = 2 F.
Q2. In the corrosion (rusting) of iron, the reaction at the cathodic region is
- Fe(s) → Fe²⁺(aq) + 2e⁻
- Fe²⁺ → Fe³⁺ + e⁻ only
- 2H₂O → O₂ + 4H⁺ + 4e⁻
- O₂(g) + 4H⁺(aq) + 4e⁻ → 2H₂O(l)
Show answer
Answer: (4) O₂(g) + 4H⁺(aq) + 4e⁻ → 2H₂O(l)
At the anodic region, iron is oxidised to Fe²⁺. Electrons travel to the cathodic region, where oxygen is reduced in the presence of H⁺: O₂ + 4H⁺ + 4e⁻ → 2H₂O.
Q3. The standard hydrogen electrode is represented as
- Zn(s) | Zn²⁺(aq, 1 M)
- Pt(s) | H₂(g, 1 bar) | H⁺(aq, 1 M)
- Cu(s) | Cu²⁺(aq, 1 M)
- Ag(s) | AgCl(s) | Cl⁻(aq)
Show answer
Answer: (2) Pt(s) | H₂(g, 1 bar) | H⁺(aq, 1 M)
The SHE has a platinum electrode coated with platinum black, in contact with H₂ gas at 1 bar and H⁺ ions at 1 M.
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