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: ΔH_rxn = H_products — H_reactants

(7.5) Standard enthalpy of reaction: ΔH^°_rxn = Σ ΔH^°_f,products − Σ ΔH^°_f,reactants

(7.6) Bond enthalpy: ΔH^°_rxn = Σ ΔH_{bonds broken} − Σ ΔH_{bonds formed} = total energy absorbed − total energy released

(7.7) Entropy:

(7.8) Second law of thermodynamics: ΔS_universe = ΔS_system + ΔS_surroundings > 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 K_eq

(7.13) Gibbs free energy from reaction quotient: