Electrochemistry Lecture Notes

Introduction

• Discussion on Electrochemistry: importance, key topics, and applications.
• Electrochemistry relevance in daily life:
  • Batteries in remotes, video games, etc.
  • Cars and commuting
  • Electronic devices (phones, laptops)
  • Drones
  • Lights
  • Corrosion and its protection (e.g., rusting of cars)
  • Electroplating (e.g., gold-plated spoons)

Principal Topics

• Electrolytic Conductance
  • Determines if a substance conducts electricity and to what extent.
  • Mostly numerical; knowledge of formulas is essential.
• Electrochemical Cells
  • Conceptual part; includes both numerical and theoretical questions.
  • Types of questions derived from cell concepts.

Key Concepts

• Electrolytic Conductance: Focus on the electrical conductance properties of electrolytes.
• Electrochemical Cells: Focus on galvanic cells and electrolytic cells:
  • Galvanic Cell (Voltaic Cell)
    • Involves spontaneous reactions (ΔG < 0)
    • Chemical energy → Electrical energy
    • Examples: Discharging phone battery
  • Electrolytic Cell
    • Involves non-spontaneous reactions (ΔG > 0)
    • Electrical energy → Chemical energy
    • Examples: Charging phone battery

Chemical Energy vs. Enthalpy

• Chemical energy referred to as Gibbs free energy (ΔG), not enthalpy (ΔH).

Electrochemical Cell Components

• Galvanic Cells:
  • Anode (negative, oxidation)
  • Cathode (positive, reduction)
  • Electrode signs: cathode (+), anode (-)
  • Electron flow: anode to cathode
  • Salt bridge ensures ion balance
• Electrolytic Cells:
  • Anode (positive, oxidation)
  • Cathode (negative, reduction)
  • Uses a battery for non-spontaneous reactions
  • Example setup: NaCl solution electrolysis

Cell Representation

• Represent cells using salt bridge, electrodes, and ion placements
• Always write cathode reaction on one side and anode reaction on the other
• Special cases: Gas ion electrodes and inert electrodes

Gibbs Free Energy and EMF of Cell

• Relationship: ΔG = -nFE_cell
• Calculating EMF using Nernst Equation
  • Non-standard conditions (Non-standard Gibbs Free Energy): ΔG = ΔG° + RTln(Q)

Faraday's Laws of Electrolysis

• Faraday's First Law: Amount of substance deposited/eroded at electrode proportional to charge passed.
• Defined terms: Faraday's constant (96,500 C/mol), number of Faradays (moles of electrons)

Practical Examples and Numerical Problems

• Practice problems on calculating EMF, Gibbs free energy, and cell representation
• Electrolysis examples with NaCl, AgNO3 solutions

Summary

• Understanding conversion between different forms of energy in electrochemical reactions is crucial
• Strong vs. weak electrolytes and their conductance differences
• Calculation methods for different conductance values and understanding of Faraday's laws

Homework and Self-Study Assignments

• Practice questions for better grasp
• Reading related sections in the textbook for more examples and detailed explanations