1. Free Energy Equilibrium and Work
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2. 17.8 Free energy and Equilibrium

3. 17.8 Free energy and equilibrium
Equilibrium occurs at the lowest value of free energy available to the reaction
This is because at this point, no more driving force exists to favor a change in one direction versus another
Any system can achieve the lowest possible free energy state by going to equilibrium and NOT TO COMPLETION.
This is because at equilibrium, the system stops short of completion and so it never fully forms product to point of stopping

4. 3 cases for free energy at Equilibrium
Case #1—DG = 0
Indicates to us that the free energy of the reactants and products are equal when every component is in its standard state
System is at equilibrium
K = 1, and we also know that pressure = 1 atm

5. Case #2 DG < 0
In this case DGo is negative (DGproducts – DGreactants)
This means that the standard free energy of the products, is less than the standard free energy of the reactants
System is NOT at equilibrium
Since the products have less free energy, the system must shift equilibrium to them (right) to reach equilibrium
K is greater than 1 now because of the shift right
Pressure of the products is greater than 1 atm at equilibrium
Pressure of the reactants is less than 1 atm at equilibrium

6. Case #3 DG > 0
In this case DGo is positive (DGoproducts – DGoreactants)
System is not at equilibrium
System will have to shift equilibrium to the left (favor reactants) to reach equilibrium
The reactants have lower free energy
The value of K will be less than 1
At Equilibrium the pressure of the products will be greater than 1
At Equilibrium the ressure of the reactants will be less than 1

7. What does all of this mean?
Positive DGo value tells me that the equilibrium will have to shift to the left to reach equilibrium
Negative DGo value tells me that the equilibrium will have to shift to the right to reach equilibrium
A DGo of 0, means that the system is at equilibrium

8. 17.9 Free Energy and work
We need to know if a process is spontaneous or non-spontaneous
We also need to know when to apply a catalyst, or when to just give up if a process is not going happen
DG essentially tells us the maximum possible amount of useful work that we can obtain from a process
If a process is spontaneous, we have free energy availible to do work, and if it’s non-spontaneous we can calculate the minimum amount of energy necessary to make it happen (if possible)
DG also allows us to determine efficiency as well
In all processes it is important to note that we never obtain the maximum amount of work from any process