Transcript Solubility Equilibria - Santa Susana High School

Solubility Equilibria
Objectives:
• 1.Compare dissolution with precipitation.
• 2.Describe equilibria for aqueous solutions of
ionic solids.
Key Terms:
• dissolution, precipitation, solubility
equilibrium, solubility product
Solubility
Ionic solids dissolve in polar solvents (water) due to the their
charged ends. Since the ionic solid forms a lattice (repeating
sequence of positive and negative ions) dissolution of the
ionic solid is fairly consistent and predictable.
• dissolution is the process in which an ionic solid dissolves in
a polar solvent
• saturation is the point where the maximum dissolution has
taken place
• precipitation is the regeneration of the ions in a solution
• solubility equilibrium is the point where the rate of
dissolution is equal to the rate of precipitation
solubility product
• The solubility product constant represents the
ions that can be dissolved in solution
– Ksp=[Na+][Cl-]
• the smaller the number the less soluble a substance is
• Ksp=[Pb2+] x [CrO42-] = 1 x 10-14
Common Ion Effect
• If an additional salt with the a similar ion is added, the
concentration of the similar ion is reduced due to the
common ion effect
• Ksp=[Pb2+] x [CrO42-] = 1 x 10-14
– Adding Pb(NO3)2to the solution shifts the equilibrium to the left
causing precipitation until the concentration of Pb is again Ksp= 1 x10-14
• The precipitation of the excess lead comes at the expense of the
chromate ion