In-Depth Notes on Thermodynamics and Electrochemistry

Yay

Entropy (S)

Level of disorder in a system, related to the number of possible arrangements of matter and energy.

Microstate

A specific arrangement of matter and energy within a system.

Change in Entropy (ΔS)

Calculation: ΔS = Sfinal - Sinitial. Positive ΔS indicates greater dispersion; negative ΔS indicates less disorder.

Standard Molar Entropy (S°)

Absolute molar entropy under standard state conditions (1 M, 1 atm).

Gibbs Free Energy (G)

Maximum amount of energy available in a system to do useful work.

Relation between ΔG, ΔH, and ΔS

ΔG = ΔH - TΔS, shows how enthalpy and entropy affect free energy.

Electrochemical Cell

Devices that convert chemical energy into electrical energy through redox reactions.

Oxidation

Loss of electrons during a redox reaction.

Reduction

Gain of electrons during a redox reaction.

Standard Reduction Potential (E°)

Electric potential for a reduction half-reaction under standard conditions.

Faraday's Law

q = nzF, where q is total charge, n is moles of product, z is number of electrons transferred.

Entropy (S)

Level of disorder in a system, related to the number of possible arrangements of matter and energy. Low entropy: solid state (high order), High entropy: gas state (high disorder).

Microstate

A specific arrangement of matter and energy within a system. The more microstates, the higher the entropy.

Factors Affecting Microstates

1. Number of Particles: More collisions increase microstates. 2. Volume: Increased volume allows for more potential microstates. 3. Phases: Different states of matter (solid, liquid, gas) influence microstates. 4. Temperature: Higher temperature leads to increased kinetic energy and possible microstates.

Second Law of Thermodynamics

Systems tend to move towards greater dispersion of matter and energy (more microstates).

Change in Entropy (ΔS)

ΔS = Sfinal - Sinitial. Positive ΔS indicates greater dispersion; Negative ΔS indicates less disorder.

Standard Molar Entropy (S°)

Absolute molar entropy under standard state conditions (1 M, 1 atm). ΔS° = Σ n S°(products) - Σ m S°(reactants).

Gibbs Free Energy (G)

Maximum energy available in a system to do useful work. ΔG = Gproducts - Greactants. When ΔG > 0, the reaction is endergonic (non-spontaneous).

Relation between ΔG, ΔH, and ΔS

ΔG = ΔH - TΔS. +ΔH corresponds to endothermic reactions; -ΔH corresponds to exothermic reactions.

Entropy Contributions

+ΔS increases entropy (supports favorability); -ΔS decreases entropy (disfavors favorability).

Favorability Conditions

Low temperature favors reactions with high -ΔH and -ΔS (enthalpy driven). High temperature favors reactions with +ΔS (entropy driven).

Kinetic Control vs. Thermodynamic Control

Kinetic Control is based on rate of reaction; Thermodynamic Control is based on thermodynamic favorability.

Electrochemical Cells

Devices that convert chemical energy into electrical energy through redox reactions. Oxidation: Loss of electrons; Reduction: Gain of electrons.

Types of Electrodes

Active Electrode: changes over time, participates in reactions. Inert Electrode: no change, does not participate in reactions.

Salt Bridge

Balances ions formed during the reaction; cations flow to cathode and anions flow to anode.

Galvanic Cells

Thermodynamically favorable (ΔG < 0), no external power source required.

Electrolytic Cells

Thermodynamically unfavorable (ΔG > 0), requires external power source.

Standard Reduction Potential (E°)

Electric potential for a reduction half-reaction under standard conditions. Ecell = Ered(cathode) - E_red(anode).

Gibbs Free Energy and Cell Potential Relation

ΔG° = -nFE_cell, where n = number of electrons, F = Faraday's constant (96485 J/V mol e-).

Equilibrium Relationships

If Keq favors products (K > 1): ΔG is negative and E°cell is positive. If Keq favors reactants (K < 1): ΔG is positive and E°cell is negative.

Electrolysis & Faraday's Law

Electrolysis: electrochemical decomposition of a compound. Faraday's Law: q = nzF, where q = total charge (C), n = moles of product, z = number of electrons transferred.