1. Common ion effect

2. Common Ion Effect
When a slightly soluble salt is dissolved in a solvent containing one of the ions found in the solute, the dissociation equilibrium is affected.
Due to the presence of a common ion, less of the salt will be able to dissolve in the solvent.
If a common ion is added to a salt solution at equilibrium, there will be a shift in the equilibrium causing some of the salt to precipitate out of solution. (LeChatelier’s Principle)

3. AgBr(s)  Ag+(aq)+ Br –(aq)
Affects of a Common Ion
AgBr(s)  Ag+(aq)+ Br –(aq)
Ksp=5.4 x 10-13
What would happen if NaBr was added to the solution above? Use LeChatelier’s principle to explain.
The equilibrium will shift left to reestablish equilibrium, causing AgBr to precipitate out of solution.
What would happen if AgNO3 was added to the solution above?

4. Quantitative Analysis of a Common ion
What is the solubility of PbCl2 in a 0.2 mol/L solution of NaCl at SATP? How does this compare to the solubility of PbCl2 in pure water?

5. Homework
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