1. Solubility Equilibrium

2. Solubility Product Constant
Ksp: solubility product constant
The product of the concentrations of the ions each raised to a power equal to the coefficient of the ion in the dissociation equation
Smaller the numerical value, lower the solubility
PbCrO4  Pb2+ + CrO42-
Ksp = [Pb2+][CrO42-]= 1.8x10-14

3. Predicting Precipitants
Ksp can be used to predict if precipitants will form
If the product of the concentration of the two ions in soln is greater than the Ksp, a precipitant will form
0.50 L of 0.002M Ba(NO3)2 is mixed with 0.50L of 0.008MNa2SO4.
Insoluble compound: BaSO4
Ksp: 1.1x10-10 (found in a chart)
[ions] are ½ because the volume was doubled
[Ba2+]x[SO42-]
(0.001M)(0.004M)=4x10-6
4x10-6>1.1x10-10 (Ksp)
Precipitant forms

4. Common Ion
Common Ion: an ion that is found in both salts and a solution.
Add lead nitrate to a saturated solution of lead chromate  dec. solubility of lead chromate
Common Ion Effect: lowering solubility from addition of a common ion

5. Entropy and Free Energy

6. Free Energy and Spontaneous Rxn.
Free Energy: energy that is available to do work
Engines ~30% efficient
Most Living things only reach 70% efficiency
Spontaneous Reaction: occurs naturally and favors the formation of products
Produce substantial amounts of products at equilibrium and release free energy
Nonspontaneous Reaction: doesn’t favor the formation of products nor give substantial amounts of products

7. Spontaneous and Nonspontaneous terms do not refer to reaction rates
Some spontaneous reactions go so slowly they appear nonspontaneous
Changes in temperature or pressure may be needed to determine if a reaction is spontaneous
Coupling a nonspontaneous and a spontaneous reaction can allow a nonspontaneous reaction to occur

8. Entropy Measure of disorder
Law of Disorder: the natural tendency is for a system to more in the direction of maximum disorder and randomness
Increase in Entropy favors spontaneous reactions
Decreases in Entropy favors nonspontaneous reactions

10. The size and direction of enthalpy changes and entropy changes together determine whether a reaction is spontaneous
Favors products and free energy is releases
Spontaneous if
Exothermic: decrease enthalpy (H)
Increase entropy (S)
Nonspontaneous if:
Endothermic: increase enthalpy (H)
Decrease entropy (S)

11. Gibbs Free Energy
Maximum amount of energy that can be coupled to another process to do useful work.
G = H - TS
Temperature (K)
G is negative: spontaneous process
G is positive: nonspontaneous process