Electrochemistry Lecture Notes

Importance and Applications of Electrochemistry

• Batteries: Used in video games, remotes, mics, and everyday devices.
• Transportation: Electric cars and other vehicles rely on electrochemistry.
• Electronics: Phones, laptops, and other electronic devices operate on principles of electrochemistry.
• Drones: Widely used in various fields, including security and photography, are based on electrochemistry.
• Lighting: All lights operate on electrochemical concepts.
• Corrosion: The rusting process of metals like iron is an electrochemical reaction.
• Electroplating: Involves coating objects with a metal layer using electrochemical processes.

Key Topics in Electrochemistry

1. Electrolytic Conductance
   • Determines if a compound will conduct electricity and to what extent
   • Most questions are numerical
   • Requires knowledge of formulas and their application
2. Electrochemical Cell
   • Conceptual understanding required
   • Questions often conceptual but numerical questions are also asked

Thermodynamics and Electrochemistry

• Chemical Energy: Denoted by Gibbs Free Energy (ΔG), not Enthalpy (ΔH)
• Spontaneous Processes: ΔG is negative
• Non-Spontaneous Processes: ΔG is positive

Types of Electrochemical Cells

1. Galvanic Cells (Voltaic Cells, Daniell Cells)
   • Spontaneous reactions (ΔG < 0)
   • Converts chemical energy into electrical energy
   • **Discharging process (e.g., using a phone)
   • Reaction: Zinc wants to oxidize (Zn → Zn²⁺ + 2e⁻); Copper wants to reduce (Cu²⁺ + 2e⁻ → Cu)
2. Electrolytic Cells
   • Non-spontaneous reactions (ΔG > 0)
   • Converts electrical energy into chemical energy
   • Charging process (e.g., charging a phone)
   • Set-up includes a battery for external force
   • Anode: Positively charged (oxidation site)
   • Cathode: Negatively charged (reduction site)

Standard Cell Potential (E°)

• Calculation: E°_cell = E°_cathode - E°_anode
• Spontaneous Reaction: Positive E°_cell
• Non-spontaneous Reaction: Negative E°_cell

Representation of Electrochemical Cells

• Galvanic Cell: Denotes cell notation; anode on the left and cathode on the right
• She: Standard Hydrogen Electrode (reduction potential = 0)
• Electrochemical Series: Ranks elements by their tendency to gain/lose electrons; helps in determining oxidation/reduction strengths

Nernst Equation

• Used to calculate the cell potential under non-standard conditions:
  • E_cell = E°_cell - (0.059/n) * log(Q)
  • Q: Reaction quotient
  • n: Number of electrons exchanged
• Relationship with Gibbs Free Energy: ΔG = -nFE°_cell

Electrolysis & Faraday's Laws of Electrolysis

• Faraday's Constant (F): 96500 C/mol
• Electrolysis: Involves oxidation at the anode and reduction at the cathode
• Preferred discharge of ions based on conductivity and electrochemical series
• **Conductance and Conductivity: R, G, ρ, K concepts and units
  • Conductance (
  • ohm⁻¹): Reciprocal of resistance (R)
  • Conductivity (K, S·cm⁻¹): Dependent on cell constant (G* = L/A)
  • Molar Conductivity: λ_m = K * (1000/C)
  • Equivalent Conductance: λ_eq = K * (1000/N)

Kohlrausch Law**

• **Definition: Infinite dilution conductance=
• Molar Conductivity (λm_infinity)= Sum of individual ion conductivities
• Calculation using strong electrolytes to estimate weak electrolyte conductance at infinite dilution.

Practical Applications and Practice Questions

• Redox Reactions, Electrolysis, and Conductance Calculation (Multiple real-world applications discussed).