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Big Ideas You will be able to Understand what K sp is Find K sp from a reaction

Solubility Product Constant K sp – equilibrium constant related to the equilibrium between a solid salt and its ions in a solution. Provides a quantitative measure of the solubility if a slightly soluble salt. Smaller K sp means that a small amount of the solid will dissolve in water Appendix D contains a list of many K sp values at 25 0 C

Solubility Product Solubility product expression - the product of the concentration of the ions involved in the equilibrium, each raised to the power of its coefficient in the equilibrium equation Same as all the other equilibrium expressions Unitless number Tells how much of the solid is dissolved to form a saturated solution

Examples BaSO 4 (s) ↔ Ba 2+ (aq) + SO 4 2- (aq) K sp = [Ba 2+ ][SO 4 2- ] CaF 2 (s) ↔ Ca 2+ (aq) + 2 F - (aq) K sp = [Ca 2+ ][2 F - ] 2

Solubility and K sp K sp only has one value for a reaction at a given temperature You can solve for K sp from solubility and solve for the solubility from K sp

Relationships between Solubility and K sp Solubility of compound (g/L) Molar solubility of compound (mol/L) Molar concentrations of ions K sp

Practice Problems 47, 53 in textbook 47a) If the molar solubility of CaF 2 is 1.24 x mol/L, what is K sp at this temperature?

Solution Step 1: Find the Dissociation Reaction 1 CaF 2 (s) ↔ 1 Ca 2+ (aq) + 2 F - (aq) Step 2: Use coefficients to find the concentration of ions Solubility of 1 CaF 2 = Concentration of 1 Ca 2+ = 1.24 x mol/L Solubility of 1 CaF 2 = Concentration of 2 F - = 2.48 x mol/L

Solution Step 3: Use the solubility product expression to solve for K sp 1 CaF 2 (s) ↔ 1 Ca 2+ (aq) + 2 F - (aq) K sp = [Ca 2+ ][2 F - ] 2 K sp = [1.24 x mol/L ][2.48 x mol/L] 2 K sp = 7.63 x 10 -9

More Problems Calculate the K sp for MgF 2 if the molar solubility of this salt is 2.7 x M. Ans. 7.9 x 10 -8

More Problems The K sp for BaCO 3 is 5.0 x What is the molarity of a saturated aqueous solution of BaCO 3 ? Ans. 7.1 x M

More Problems The K sp for Fe(OH) 2 is 4.1 x What is the approximate pH of a saturated solution of Fe(OH) 2 ? Ans. 9.00

More Problems The solubility of AgCl in pure water is 1.3 x 10 –5 M. What is its solubility in seawater where the [Cl – ] = 0.55 M? (K sp of AgCl = 1.8 x 10 –10 )

AgCl (s)Ag + (aq) +Cl - (aq) IN/A00.55 M CN/A+x EN/A+x x K sp = [x][.55+x] K sp =.55x 1.8 * =.55x x = 3.3* = [Ag + ] = [AgCl]