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Introduction to Electrochemistry and Cells
Jul 9, 2024
Electrochemistry
Interconversion of Energy
Electrochemistry
: The mutual conversion of chemical energy and electrical energy.
Electrochemical Cell
: A device in which this conversion occurs.
Two Types of Cells
:
Galvanic or Voltaic Cell
Electrolytic Cell
Galvanic Cell vs. Electrolytic Cell
Galvanic (Voltaic) Cell
:
Spontaneous redox reaction (ΔG < 0)
Conversion of chemical energy into electrical energy
Indirect redox reaction
Electrolytic Cell
:
Non-spontaneous redox reaction (ΔG > 0)
Conversion of electrical energy into chemical energy
Direct redox reaction
Galvanic Cell Structure
Oxidation Half Cell
(Anode): Negatively charged electrode.
Reduction Half Cell
(Cathode): Positively charged electrode.
Salt Bridge
: Completes the circuit internally and maintains the electrical neutrality of the electrolyte solution.
Each Half Cell
: A metal electrode dipped in its electrolyte solution.
Working of Galvanic Cell
Zinc Electrode
: Zn -> Zn²⁺ + 2e⁻ (Oxidation Half Cell)
Copper Electrode
: Cu²⁺ + 2e⁻ -> Cu (Reduction Half Cell)
Overall Reaction
: Zn + Cu²⁺ -> Zn²⁺ + Cu
Cell Representation
: Zn | Zn²⁺ || Cu²⁺ | Cu
Electrode Potential
Definition
: Potential difference between the electrode and electrolyte. Measured in volts.
Standard Electrode Potential
: Measured at 25°C, 1 molar concentration, 1 ATM pressure.
EMF
: Potential difference between cathode and anode (E cathode - E anode)
Nernst Equation
Formula
: E_cell = E°_cell - (0.0591/n) log(Q)
**Useful for calculating EMF under non-standard conditions.
Gibbs Free Energy
Formula
: ΔG° = -nFE°_cell
Negative ΔG indicates a spontaneous reaction
Conductivity and Conductance
Conductivity (κ)
: C = kA / l
Conductance (G)
: G = 1/R
Conductivity Formula
: G_star x conductance
Conductivity of Cells
Effect of Dilution
: Conductivity decreases while molar conductance increases.
Debye Huckel
: λ_m^∞ = λ⁺ + λ⁻
Quantitative Analysis of Electrolysis
Faraday's Law
: m = (E × I × t) / (n × 96500)
Calculating products at cathode and anode.
Preferential Discharge Theory
Importance of Discharge Potential
Anode oxidizes giving off gas while the cathode reduces easily and deposits.
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