1. CHAPTER 15 AP CHEMISTRY

2. COMMON ION EFFECT If you have HC 2 H 3 O 2 (aq) H + (aq) + C 2 H 3 O 2 - (aq) If you have HC 2 H 3 O 2 (aq) H + (aq) + C 2 H 3 O 2 - (aq) What would happen if you added the salt NaC 2 H 3 O 2 ? What would happen if you added the salt NaC 2 H 3 O 2 ? Addition of C 2 H 3 O 2 - would cause the system to shift to the left Addition of C 2 H 3 O 2 - would cause the system to shift to the left This is called the COMMON-ION EFFECT This is called the COMMON-ION EFFECT Page 682 example Page 682 example

3. BUFFER Prepared by adding both the weak acid HB and its conjugate base B - to water Prepared by adding both the weak acid HB and its conjugate base B - to water [H + ] = k a [HB] = k a nHB [H + ] = k a [HB] = k a nHB [B - ] nB - [B - ] nB - Effect of adding strong acids or bases to a buffer Effect of adding strong acids or bases to a buffer HB(aq) + OH - (aq) ---> H 2 O(l) + B - (aq) HB(aq) + OH - (aq) ---> H 2 O(l) + B - (aq) B - (aq) + H + (aq) ---> HB(aq) B - (aq) + H + (aq) ---> HB(aq) H + and OH - ions are consumed so the pH is not affected H + and OH - ions are consumed so the pH is not affected Buffered solutions are most effective when concentrations of H + and base B - are about the same Buffered solutions are most effective when concentrations of H + and base B - are about the same Read chapters 19 and 20 notes are due the first day of fourth term Read chapters 19 and 20 notes are due the first day of fourth term

4. CONTINUED Henderson-Hasselbach equation is used in biology to calculate the pH of the buffer Henderson-Hasselbach equation is used in biology to calculate the pH of the buffer pH = pk a + log [base] pH = pk a + log [base] [acid] [acid]

5. ACID-BASE TITRATION Read and study pages 699-711 Read and study pages 699-711 Titration curve Titration curve –Graph of pH to concentration strong acid - strong base page 697 strong acid - strong base page 697 H + (aq) + OH - (aq) H 2 O(l) k = 1/k w = 1/(1 X 10 -14 ) H + (aq) + OH - (aq) H 2 O(l) k = 1/k w = 1/(1 X 10 -14 ) –pH = 7, change rapidly as you near the end point

6. CONTINUED Weak acid-strong base Weak acid-strong base HA(aq) + OH - (aq) A - (aq) + H 2 O(l) k =1/k b HA(aq) + OH - (aq) A - (aq) + H 2 O(l) k =1/k b pH > 7 at end point, change occurs slowly at end point pH > 7 at end point, change occurs slowly at end point Strong acid-weak base Strong acid-weak base H + (aq) + A - (aq) HA(aq) k = 1/k a H + (aq) + A - (aq) HA(aq) k = 1/k a pH < 7, at end point, change occurs slowly at end point pH < 7, at end point, change occurs slowly at end point Titration of polyproptic acids Titration of polyproptic acids When neutralization steps are separated the substance will show a titration curve with multiple equivalence points When neutralization steps are separated the substance will show a titration curve with multiple equivalence points

7. INDICATORS HIn(aq) H + (aq) + In - (aq) In = indicator HIn(aq) H + (aq) + In - (aq) In = indicator HIn and In - have different colors, the wavelengths that bounce back are different when hydrogen is attached HIn and In - have different colors, the wavelengths that bounce back are different when hydrogen is attached Color of a solution depends on the concentration ratio Color of a solution depends on the concentration ratio [HIn] = [H + ] [HIn] = [H + ] [In - ] ka [In - ] ka Endpoint occurs when [H + ] = ka Endpoint occurs when [H + ] = ka About pH 5 for methyl red, pH 7 for bromothymol blue, and pH 9 for phenolphthalein About pH 5 for methyl red, pH 7 for bromothymol blue, and pH 9 for phenolphthalein Read pages 711-716 Read pages 711-716

8. SOLUBILITY EQUILIBRIA If Q(ion product) is compared with the ksp, the following can be said If Q(ion product) is compared with the ksp, the following can be said Q > ksp ppt occurs until Q = ksp Q > ksp ppt occurs until Q = ksp Q = ksp equilibrium (saturation has occured) Q = ksp equilibrium (saturation has occured) Q < ksp solid dissolves until Q = ksp Q < ksp solid dissolves until Q = ksp AgCl(s) Ag + (aq) + Cl - (aq) AgCl(s) Ag + (aq) + Cl - (aq) Slightly soluble ksp found on page 718 Slightly soluble ksp found on page 718 ksp = [Ag + ][Cl - ] ksp = [Ag + ][Cl - ]

9. CONTINUED the solubility of slightly soluble salts containing basic anions will increase as the [H + ] increases the solubility of slightly soluble salts containing basic anions will increase as the [H + ] increases Looking at the solubility of a salt Looking at the solubility of a salt In pure water it is the same as the reaction In pure water it is the same as the reaction

10. CONTINUED Complex ions Complex ions –Metal ions with Lewis bases bonded to it page 958, 731-737 Amphoterism Amphoterism –Behavior of water molecules around a metal ion Read pages 724-730 Read pages 724-730