Chapter 16 Aqueous Equilibria: Applications 1. neutralization reactions 2. common ion effect; buffers 3. titrations strong acid - strong base strong - weak weak - weak polyprotic acid - strong base 4. solubility equilibria review precipitation reactions and solubility rules Ksp & solubility common ion effect solubility & pH 5. complex ion formation Kf solubility 6. selective precipitation; qualitative analysis: skip Chapter 16 Notes

Ag1+(aq)+2NH3(aq) Ag(NH3)21+ Zn2+(aq)+4OH1-(aq) Zn(OH)42- 5. complex ion formation what is a “complex ion”: an ionic Lewis acid-base species that forms between a cation (Lewis acid) and an anion or compound with a lone pair (Lewis base) examples: Ag1+(aq)+2NH3(aq) Ag(NH3)21+ Zn2+(aq)+4OH1-(aq) Zn(OH)42- complex ions are very stable: the equilibrium constant for the formation of a complex ion is very large Chapter 16 Notes

1. Calculate the solubility of AgBr(s) in water; Ksp(AgBr)=5.4x10-13. 5. complex ion formation example: 1. Calculate the solubility of AgBr(s) in water; Ksp(AgBr)=5.4x10-13. 2. Na2(S2O3) is added to a saturated solution of AgBr. Ag+ forms a complex ion with S2O3-2; the complex ion, Ag(S2O3)2-3 has Kf=2.9x1013. Let's see what happens. a. What are the predominant species in solution? What secondary species can form? b. What reactions, if any, can occur between any two primary species? What reactions, if any, can occur between a primary and a secondary species? Chapter 16 Notes

5. complex ion formation example cont’d c. Write the balanced chemical equation that shows the formation of the secondary species. Write the balanced chemical equation that shows the reaction between the primary and secondary species. Add the two equations together to get the net, overall reaction which occurs when Na2(S2O3) is added to a saturated solution of AgBr.. d. What is the equilibrium constant for the net reaction? Does S2O3-2 increase or decrease the solubility of AgBr? Why? Chapter 16 Notes

e. Now calculate the solubility of AgBr in S2O3-2. 5. complex ion formation example cont’d. e. Now calculate the solubility of AgBr in S2O3-2. Chapter 16 Notes

b. A lot of NH3 is added to the solution from part a. 5. complex ion formation another example: Using Table C.6 (Appendix C) in your textbook, and using the solubility rules, state what you would observe if the following solutions are mixed. Write balanced chemical equations to support your answers. a. A solution of CuCl2 is made slightly basic with the addition of a small amount of NH3. b. A lot of NH3 is added to the solution from part a. c. NaCN is added to a saturated solution of FeS. d. A solution of Cr(NO3)3 is made slightly basic with the addition of a small amount of NaOH. e. A lot of NaOH is added Chapter 16 Notes