MCAT General Chemistry Review - Alexander Stone Macnow, MD 2019-2020
Thermochemistry
Equations to Remember
(7.1) First law of thermodynamics: ΔU = Q — W
(7.2) Heat transfer (no phase change): q = mcΔT
(7.3) Heat transfer (during phase change): q = mL
(7.4) Generalized enthalpy of reaction: ΔHrxn = Hproducts — Hreactants
(7.5) Standard enthalpy of reaction: ΔH°rxn = Σ ΔH°f,products − Σ ΔH°f,reactants
(7.6) Bond enthalpy: ΔH°rxn = Σ ΔHbonds broken − Σ ΔHbonds formed = total energy absorbed − total energy released
(7.7) Entropy:
(7.8) Second law of thermodynamics: ΔSuniverse = ΔSsystem + ΔSsurroundings > 0
(7.9) Standard entropy of reaction: ΔS°rxn = Σ ΔS°f,products − Σ ΔS°f,reactants
(7.10) Gibbs free energy: ΔG = ΔH — TΔS
(7.11) Standard Gibbs free energy of reaction: ΔG°rxn = Σ ΔG°f,products − Σ ΔG°f,reactants
(7.12) Standard Gibbs free energy from equilibrium constant: ΔG°rxn = —RT ln Keq
(7.13) Gibbs free energy from reaction quotient: