2. Free Energy and Pressure
G = G° + RT ln(P) or ΔG = ΔG° + RT ln(Q)
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3. Sketch graphs of: G vs. P H vs. P
CONCEPT CHECK!
Sketch graphs of:
G vs. P
H vs. P
ln(K) vs. 1/T (for both endothermic and exothermic cases)
G vs. P: A natural log graph (levels off as P increases).
H vs. P: no relationship (slope of zero).
lnK vs 1/T: endothermic - straight line, negative slope
exothermic - straight line, positive slope
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4. The Meaning of ΔG for a Chemical Reaction
A system can achieve the lowest possible free energy by going to equilibrium, not by going to completion.
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5. The equilibrium point occurs at the lowest value of free energy available to the reaction system.
ΔG = 0 = ΔG° + RT ln(K)
ΔG° = –RT ln(K)
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6. Change in Free Energy to Reach Equilibrium
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8. Maximum possible useful work obtainable from a process at constant temperature and pressure is equal to the change in free energy.
wmax = ΔG
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9. All real processes are irreversible.
Achieving the maximum work available from a spontaneous process can occur only via a hypothetical pathway. Any real pathway wastes energy.
All real processes are irreversible.
First law: You can’t win, you can only break even.
Second law: You can’t break even.
As we use energy, we degrade its usefulness.
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