thermochem

adiabatic process

no heat is exchanged between the system and the environment

thermal energy of the system is constant throughout the process

isothermal process

system’s temperature remains constant

total energy of the system (U) is constant throughout the process

isobaric process

pressure of the system is constant

isovolumetric (isochoric) process

no change in volume

no work is performed; ΔU = Q

Hess’s Law

enthalpy changes of reactions are additive

second law of thermodynamics (entropy)

energy spontaneously disperses from being localized to becoming spread out if it is not hindered from doing so

ΔS = Q_rev/T

Q_rev = heat that is gained or loss in a reversible process

ΔS_universe = ΔS_system + ΔS_surroundings > 0

Gibbs free energy

ΔG = ΔH - TΔS

endergonic = system releases energy (ΔG < 0) and is spontaneous

exergonic = system gains energy (ΔG > 0) and is nonspontaneous

effect of ΔH and ΔS on ΔG

ΔH	ΔS	outcome
+	+	spontaneous at high T
+	-	nonspontaneous at all T
-	+	spontaneous at all T
-	-	spontaneous at low T

standard Gibbs free energy

ΔG_rxn^o = ΣΔG_f,products^o - ΣΔG_i,reactants^o

Free energy, K_eq, and Q

ΔG_rxn^o = -RT ln(K_eq)

ΔG_rxn = ΔG_rxn^o + RT ln(Q) = RT ln(Q/K_eq)