Thermodynamics Flashcards
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)]
deltaG*_total =
deltaG_reaction 1 + deltaG_reaction 2 + …
the free energy of formation (delta G_f*) is the…
change in free energy when 1 mol of a compound forms from its constituent elements in their standard states
deltaG =
deltaG* + RTln(Q)
deltaG* =
-RTln(K)
w_gas =
-P_ext(deltaV)
1 L(atm) =
101.325 J
