Overview

Thermodynamics studies the flow of energy in chemical systems. It focuses on changes in enthalpy (ΔH), entropy (ΔS), and free energy (ΔG) to determine whether a reaction is spontaneous, requires energy, or releases energy. Understanding thermodynamic principles is essential for predicting reaction direction and efficiency.

Key Concepts and Structures

• System vs. Surroundings: The system is the part of the universe being studied; everything else is the surroundings.
• First Law of Thermodynamics: Energy cannot be created or destroyed—only transferred or transformed.
  ΔE = q + w
• Enthalpy (ΔH): The heat content of a system.
  
  • ΔH < 0 → exothermic (releases heat)
  • ΔH > 0 → endothermic (absorbs heat)
• Entropy (ΔS): A measure of disorder or randomness. Increases with more microstates, more particles, phase changes (solid → liquid → gas).
• Gibbs Free Energy (ΔG): Predicts spontaneity of a process.
  ΔG = ΔH - TΔS
  • ΔG < 0 → spontaneous
  • ΔG > 0 → nonspontaneous
  • ΔG = 0 → equilibrium
• Standard State Conditions: 1 atm, 25°C, 1 M concentration.
• Hess’s Law: The total enthalpy change of a reaction is the sum of the enthalpy changes for each step.
• Calorimetry: Measures heat transfer. Common equation: q = mcΔT
• Heat Capacity (C): Amount of heat needed to raise temperature by 1°C. Specific heat is per gram.
• State Functions: Properties that depend only on initial and final states (e.g., ΔH, ΔS, ΔG) and not the path taken.

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