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Electrochemistry

Electrochemical cells, Nernst equation, conductance

Key Concepts
  • Galvanic (voltaic) cell: spontaneous redox reaction generates electricity
  • Electrolytic cell: non-spontaneous reaction driven by external electricity
  • Standard hydrogen electrode (SHE): E° = 0 V (reference)
  • Higher reduction potential → stronger oxidising agent
  • Faraday's laws: mass deposited proportional to charge passed and equivalent weight
Important Formulae
Cell EMF E_cell = E°_cathode − E°_anode
Nernst equation E = E° − (RT/nF) ln Q
ΔG and EMF ΔG° = −nFE°
Faraday's first law m = (M/nF) × Q = (M/nF) × It
Kohlrausch's law Λ°_m = Σ(λ° ions)
Quick Tips
  • Faraday constant F = 96,485 C/mol ≈ 96,500 C/mol.
  • At equilibrium: E_cell = 0; ΔG = 0; Nernst gives E° = (RT/nF) ln K.
  • Specific conductance decreases on dilution; molar conductance increases.
Sample Practice Questions

  1. During charging of a lead-acid battery, PbSO₄ at anode converts to:

    • Pb
    • PbO₂
    • PbO
    • Pb²⁺
    Show answer

    Answer: PbO₂

  2. Molar conductance Λm = κ × 1000/M where M is:

    • Molar mass
    • Molarity of solution
    • Molality
    • Mass of solvent
    Show answer

    Answer: Molarity of solution

  3. Electrolytic conductance increases with dilution because:

    • Temperature decreases
    • More ions are available and interionic forces decrease
    • Viscosity increases
    • Solvent evaporates
    Show answer

    Answer: More ions are available and interionic forces decrease

  4. Faraday's second law states that when same charge passes through different electrolytes, mass deposited is proportional to:

    • Molar mass alone
    • Atomic number
    • Equivalent mass (M/n)
    • Charge of ion only
    Show answer

    Answer: Equivalent mass (M/n)

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Practice Questions

Practice 20 randomly selected NEET questions on Electrochemistry. Answers are revealed after each question.

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