Electrochemistry Lecture Notes

Introduction

• Instructor: Ajay
• Topic: Electrochemistry (Physical Chemistry)
• Chapters to Cover: Plan to cover 3 chapters in 10 days

Importance of Electrochemistry

• Key chapter in Physical Chemistry
• Considered difficult by many students
• Concepts involved are crucial for students, especially those targeting exams like JEE Mains, NEET, and EAMCET
• Usually appears with 1-2 questions in these exams

Key Chapter Concepts

• Electrolytes and Non-Electrolytes: Solutions that conduct electricity and those that don't
  • Electrolytes dissociate into ions in solution
  • Non-electrolytes do not dissociate into ions

Examples of Electrolytes

• Salt Solution: NaCl -> Na⁺ + Cl⁻ (Conducts electricity)
• Water (H₂O): Weak electrolyte (Barely dissociates)
• Benzene (C₆H₆): Non-electrolyte (Does not dissociate)

Types of Electrolytes

• Strong Electrolytes: Nearly 100% dissociation (e.g., HCl, NaOH, KCl)
• Weak Electrolytes: Partial dissociation (e.g., CH₃COOH, NH₃)

Conductance and Conductivity

• Conductance (C or G): Measure of the flow of electric charge through an electrolyte solution

  • Inverse of Resistance (R): C = 1/R
  • Unit: Siemens (S) or Ohm⁻¹
  • Factors affecting conductance: Number of ions, mobility of ions, etc.

• Conductivity (κ or kappa): Conductance of 1 cm³ of an electrolyte solution

  • Unit: Siemens per centimeter (S/cm or cm⁻¹)
  • κ = 1/ρ (resistivity)
  • κ = C (Conductance) × (l/A)
  • Factors: Nature of electrolyte, ion concentration, temperature, etc.

Example Calculation

• Given: Conductance, Cell Constant, and Solution Concentration
• Calculate: Conductivity and Molar Conductance

Molar Conductivity (Λm)

• Definition: Conductivity of an electrolyte solution divided by its molarity (M)
  • Λm = κ × 1000/M
  • Unit: S cm² mol⁻¹
• Factors: Increases with dilution due to decreased ion interaction

Equivalent Conductivity (Λeq)

• Definition: Conductivity of a solution containing 1 gram-equivalent of electrolyte
  • Λeq = κ × 1000/N (where N is the normality)
  • Unit: S cm² equivalent⁻¹

Relationships and Units

• Conductance and Conductivity: G = κ × (l/A)
• Molar and Equivalent Conductance: Λm = κ × 1000/M and Λeq = κ × 1000/N
• Important Units: Siemens (S), S cm² mol⁻¹, S cm² equivalent⁻¹

Exercised Example Problems

• Multiple problems were solved, applying the formulas for calculating conductance, conductivity, molar conductivity, and equivalent conductivity.

Conclusion

• Emphasis on understanding basic concepts first
• Thorough practice required for mastery
• Preparing with previous years' questions is beneficial
• Upcoming lecture topics will dive into electrochemical potential and other detailed concepts in electrochemistry.

Important Notes

• Take detailed notes and practice problems regularly
• Concentrate on weak areas and ensure clarity of fundamental principles