Thermodynamics Flashcards
(30 cards)
spontaneity is determined by…
comparing the free energy of the system before the reaction with the free energy of the system after reaction
the most likely macrostate of a system is the one with…
the greatest entropy
entropy change is favorable when…
the result is a more random system
deltaS =
S_f - S_i
Second Law of Thermodynamics
the entropy of the universe increases in a spontaneous process and remains unchanged in an equilibrium process
deltaS_univ =
deltaS_sys + deltaS_surr
in terms of S
exothermic process
deltaS_surr > 0
in terms of S
endothermic process
deltaS_surr < 0
deltaS_surr =
-deltaH/T
deltaS_fusion =
deltaH_fusion/T_f`
deltaG =
deltaH_sys - T(deltaS_sys)
spontaneous process
deltaS_univ = deltaS_sys + deltaS_surr > 0
equilibrium process
deltaS_univ = delta S_sys + deltaS_surr = 0
if deltaG < 0
the reaction is spontaneous in the forward direction
if deltaG > 0
the reaction is nonspontaneous as written
if deltaG = 0
the reaction is at equilibrium
if H is negative and S is positive
spontaneous at all temps
if H is positive and S is positive
spontaneous at high temps
if H is negative and S is negative
spontaneous at low temps
if H is positive and S is negative
not spontaneous at any temp
absolute entropy
the amount of energy a substance has due to dispersion of energy through its particles
Third Law of Thermodynamics
for a perfect crystal at absolute zero, the absolute entropy = 0 J/(mol)(K)
the larger the molar mass…
the larger the entropy
deltaG*_reaction =
sum[ndeltaG_f(products)] - sum[ndeltaG_f(reactants)]
