Thermochemistry Flashcards
process occurs at constant temperature
isothermal
process exchanges no heat with environment
adiabatic
process occurs at constant pressure
isobaric
process occurs at constant volume
isochoric (isovolumetric)
describe the physical properties of an equilibrium state; they are pathway independent; include: pressure, density, temperature, volume, enthalpy, internal energy, Gibbs free energy, and entropy
state functions
T = 298 K, P = 1 atm, 1M concentrations
standard conditions
T = 273 K, P = 1 atm; used for gas law calculations
standard temperature and pressure
most prevalent form of an element under standard conditions
standard state
exist at characteristic temperatures and pressures; include: fusion (melting), freezing (crystallization or solidification), vaporization (evaporation or boiling), condensation, sublimation, and deposition
phase changes
at temperatures above this point, liquid and gas phases are indistinguishable
critical point
temperature and pressure when all three phases of matter exist in equilibrium
triple point
graphs the phases and phase equilibria for a system as a function of temperature and pressure
phase diagram
a scaled measure of the average kinetic energy of a substance
temperature
the transfer of energy that results from differences of temperature between two substances
heat
a measure of the potential energy of a system found in intermolecular attractions and chemical bonds
enthalpy
heat (q)
q = mc∆T
where:
c = specific heat
q = mL
where:
L = latent heat
a measure of the degree to which energy has been spread throughout a system or between a system and its surroundings; maximized at equilibrium; unit = J/mol*K
entropy
entropy (S)
S = Q(rev) / T
where:
Q(rev) = heat gained or lost in a reversible process
derived from both enthalpy and entropy values for given system; also depends on temperature
Gibbs free energy
change in Gibbs free energy (∆G)
∆G = ∆H - T∆S
determines whether a process is spontaneous or nonspontaneous
change in Gibbs free energy (∆G)
reaction proceeds in forward direction (spontaneous)
∆G < 0
reaction is in dynamic equilibrium when ∆G = __
∆G = 0
reaction proceeds in reverse direction (nonspontaneous)
∆G > 0
∆G°(rxn)
∆G°(rxn) = -RT ln K(eq)
