Chem - Thermochemistry

Isobaric process

pressure of system is constant

Open system

both heat and matter are freely exchanged with the surroundings

Closed System

only heat exchanged

Isolated system

neither heat nor matter exchanged

Isothermal process

system temperature is constant

Adiabatic process

no heat exchanged between system and environment

Isovolumetric (isochoric) process

no change in volume

Enthalpy of fusion (ΔH_fus)

determine heat transferred in phase change at solid-liquid boundary

positive - if solid → liquid

negative - if liquid → solid

Enthalpy of vaporization (ΔH_vap)

for the liquid-gas boundary, q = mL

Enthalpy (H)

ΔH_rxn = H_products - H_reactants

Hess’s Law

enthalpy changes of reactions are additive; ΔH_{reactants → elements} = - ΔH_{elements → reactants}

Bond enthalpy / bond dissociation energies

H_{bonds broken} - H_{bonds formed} = total energy absorbed - total energy released

Gibbs Free energy

ΔG = ΔH - TΔS

Standard Gibbs free energy from equilibrium constant

ΔG_rxn = -RT lnK_eq

Entropy

ΔS = Q_rev / T