Electrochemistry Lecture Notes

Introduction

• Importance and relevance of electrochemistry
• Common applications in daily life (batteries, drones, lights, etc.)
• Electrochemistry surrounds various everyday technologies

Electrochemistry Overview

1. Electrolytic Conductance
   • Determines if a compound/electrolyte will conduct electricity
   • Numerical approach: equations, formulas, application
2. Electrochemical Cells
   • Conceptual part: types of cells and their principles
   • Galvanic (Voltaic) Cell: spontaneous processes
   • Electrolytic Cell: non-spontaneous processes, require external force (battery)

Chemical Energy in Reactions

• Chemical energy: energy changes during chemical reactions
• Misconception: Chemical energy ≠ Enthalpy (ΔH)
• Correct understanding: Chemical energy = Gibbs Free Energy (ΔG)
• ΔG interpretations: Negative for spontaneous, positive for non-spontaneous

Types of Electrochemical Cells

1. Galvanic Cell
   • Spontaneous reactions; ΔG is negative
   • Galvanic cell setup: two containers, Zn and Cu electrodes, spontaneous electron flow
   • Zinc oxidizes (anode); Copper reduces (cathode)
   • Electron flow: Anode to Cathode
   • Current flow: Cathode to Anode (opposite to electron flow)
   • Salt bridge: maintains electrical neutrality
2. Electrolytic Cell
   • Non-spontaneous reactions; ΔG is positive
   • Set up with a battery; positive and negative electrodes
   • Na+ ions go to negative terminal (cathode), Cl- to positive terminal (anode)
   • Redox reactions: reduction at cathode, oxidation at anode

Cell Representation and Standard Conditions

• Standard Hydrogen Electrode (SHE): Reference for calculating reduction and oxidation potentials
• Electrochemical Series: Ranks elements based on potential
• Cell EMF Calculations (Nernst equation for non-standard conditions)
  • Equation: E_cell = E°_cell - (0.059/n) log (Q)
  • Standard EMF & equilibrium conditions: useful for determining spontaneity

Practical Applications

1. Faraday's Law of Electrolysis
   • Charge on one mole of electrons (1 Faraday = 96500 C)
   • Calculation of elements deposited/evolved during electrolysis
   • Application in daily life (like deposition of Na when mercury electrode is used)
2. Electrolytic Conductance
   • Resistance, conductance, resistivity, conductivity
   • Important formulas:
     • R = ρ (L/A)
     • 1/R = G (Conductance)
     • G = K * (A/L)
     • G* (cell constant) = L/A
   • Units and conversions (Ohms, Siemens, etc.)

Kohlrausch Law

• Independent Migration of Ions: Each ion contributes fixed value to conductance
• Calculation for weak electrolytes: Use values from strong electrolytes and cross-contribute

Summary and Key Points

• Detailed structure of galvanic and electrolytic cells
• Concepts of chemical energy (Gibbs Free Energy)
• Methods of calculating EMF using standard and non-standard conditions
• Practical examples and numerical problem-solving techniques

Practice Problems

• Questions comparing elements' reduction potentials
• Standard electrode potential problems
• Nernst equation applications
• Electrolytic conductance scenarios
• Faraday’s law applications and calculations

Conclusion

• Electrochemistry's theoretical foundation
• Importance of practice in mastering concepts and calculations
• Emphasis on practical relevance and everyday applications