1. CHAPTER 17 - SOLUBILITY AND PRECIPITATION

2. Read intro on page 560 Dissolution CaCl 2(s) ↔ Ca +2 (aq) + 2 Cl - (aq) CaCl 2(s) ↔ Ca +2 (aq) + 2 Cl - (aq)Precipitation Ca +2 (aq) + 2 Cl - (aq) ↔ CaCl 2(s) K sp = [Ca +2 ] [Cl - ] 2

3. Students complete practice problems 1 & 2 on page 565 We can look up the solubility product constant of many materials at 25 o C. (see page 566). Demonstrate problem #2 on page 567 Students complete problems 3 & 4 on page 567.

4. USING K SP TO CALCULATE ION CONCENTRATIONS Review writing ionic equations (worksheet). Students earmark polyatomic ion page in notes (or ask on a test). Complete sample problem 3. Students complete practice problems 5 & 6

5. PREDICTING THE FORMATION OF A PRECIPITATE Insert the ion concentrations into the K sp equation and calculate the “K sp ”. Since we do not know if the solution is at equilibrium, we call the “K sp ” the ion product quotient (Q) (same as the reaction product quotient).

6. If Q = Ksp the solution is at equilibrium. If Q > Ksp the solution is supersaturated and a precipitate will form. If Q < Ksp the solution is unsaturated. Chemical reactions that result in a precipitate form a product that has a Q greater than the precipitate’s Ksp.

7. Can also predict a precipitate rather than calculate The rules on page 574 can be used to predict a precipitate. A double replacement reaction will take place if an insoluble (or slightly soluble) compound is formed. AgNO 3(aq) +KBr (aq) → AgBr (s) +KNO 3(aq) A double replacement reaction will also take place if water or a gas is formed. A double replacement reaction will also take place if water or a gas is formed.

8. Demonstrate sample problem #4 Assign practice problems 7 & 8.

9. Net ionic equation A net ionic equation includes only the change. Total equation AgNO 3(aq) + KBr (aq) → AgBr (s) + KNO 3(aq) Net Ionic Equation Ag + (aq) + Br - (aq) → AgBr (s) NO 3 - and K + are called “spectator ions” because they do not participate in the reaction

10. The common-ion effect This is a shift in the equilibrium because the concentration of one of the equilibrium ions is changed. (Le Chatelier’s Principle) CaSO 4(s) ↔ Ca +2 (aq) + SO 4 -2 (aq) What will happen if Na 2 SO 4 is added? Will shift to the left More CaSO 4 will precipitate out.