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Electrochemistry — Revision Notes

Punjab Board · Class 12 · Chemistry

Electrochemistry revision notes for Punjab Board Class 12 Chemistry: 4 topics in quick points. Part of the Punjab Board Class 12 Chemistry syllabus.

45 questions36 flashcards6 formulas & key relations5 concepts

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Key Topics to Revise

1

Electrochemical Cells – Galvanic and Electrolytic

  • An electrochemical cell has two metallic electrodes dipping in an electrolytic solution.
  • Galvanic (Voltaic) Cell: Converts chemical energy of a SPONTANEOUS redox reaction into electrical energy. Example: Daniell Cell.
  • Electrolytic Cell: Uses ELECTRICAL ENERGY to carry out NON-SPONTANEOUS chemical reactions.
2

Nernst Equation

  • The Nernst equation gives the electrode potential or cell potential at any given concentration (not just standard conditions).
  • For electrode reaction: M^n+(aq) + ne⁻ → M(s), the electrode potential is given by the Nernst equation.
  • General Nernst equation for a cell: E_cell = E°_cell – (RT/nF) ln Q
3

Conductance of Electrolytic Solutions

  • Resistance (R) of a conductor: R = ρl/A (in ohms, Ω); where ρ = resistivity, l = length, A = cross-section area.
  • Resistivity (ρ): Resistance of a material of 1 m length and 1 m² cross-section. SI unit: Ω m.
  • Conductance (G) = 1/R = κA/l. SI unit: Siemens (S) or Ω⁻¹.
4

Variation of Molar Conductivity and Kohlrausch's Law

  • STRONG ELECTROLYTES (e.g., NaCl, KCl, HCl): Λm increases SLOWLY with dilution. Debye-Hückel-Onsager equation: Λm = Λ°m – A√c (Debye-Hückel-Onsager or Kohlrausch equation).
  • Plot of Λm vs √c is a straight line for strong electrolytes. Intercept = Λ°m, Slope = –A.
  • WEAK ELECTROLYTES (e.g., CH₃COOH, NH₄OH): Λm increases STEEPLY with dilution, especially at very low concentrations.

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Full Notes

Key Concepts

Electrochemical cells consist of two electrodesIn galvanic cellsElectrolytic cells require external electrical energyStandard electrode potential is the potentialThe Nernst equation relates electrode potential

Frequently Asked Questions

What are the important topics in Electrochemistry for Punjab Board Class 12 Chemistry?
Key topics in Electrochemistry include Electrochemical Cells – Galvanic and Electrolytic, Nernst Equation, Conductance of Electrolytic Solutions, Variation of Molar Conductivity and Kohlrausch's Law. Study these first, then practise questions on each for the Punjab Board Class 12 board exam.
How should I revise Electrochemistry for the Punjab Board Class 12 board exam?
Learn the core ideas first, then work through the 45 practice questions on Electrochemistry. Revise definitions regularly and use flashcards for quick recall before the exam.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

More resources for Electrochemistry

All Punjab Board Class 12 Chemistry Revision Notes

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