🔥 Thermochemistry — Advanced#

Scope — Thermodynamic state functions, temperature dependence, and links between enthalpy, entropy, and spontaneity.

Key concepts#

• State functions — properties (H, S, G) dependent only on state, not path.
• Entropy (S) — measure of energy dispersal or number of accessible microstates.
• Gibbs free energy (G) — criterion for spontaneity at constant temperature and pressure.

Seed Q&A triads#

• Q: How are enthalpy and entropy combined to predict spontaneity?
  A: Through Gibbs free energy: ΔG = ΔH − TΔS; processes with ΔG < 0 are spontaneous.

• Q: Why can an endothermic reaction be spontaneous?
  A: A sufficiently large positive entropy change can outweigh positive ΔH, making ΔG negative.

• Q: How does temperature influence reaction favorability?
  A: Temperature scales the entropy term (TΔS), shifting the balance between enthalpy and entropy contributions.

Contributor prompts and extensions#

• Add a worked example calculating ΔG at different temperatures and interpreting the result.
• Include a short discussion of phase transitions and their characteristic ΔH and ΔS values.
• Connect thermochemistry to equilibrium constants via ΔG° = −RT ln K.

Advanced exercises#

• Analyze how changes in temperature alter equilibrium position for reactions with different ΔH and ΔS signs.