1. Acids & Bases Calculating Ka from % Dissociation Polyprotic Acids Properties of Salts

2. Example Lactic acid (HC 3 H 5 O 3 ) is a waste product that accumulates in the muscle during exertion, leading to pain & a feeling of fatigue. A 0.100 M solution is 3.7% dissociated. Calculate K a.

3. Example I C E HC 3 H 5 O 3  H + + C 3 H 5 O 3 -

4. Polyprotic Acids More that one ionizable H + H + come off one at a time Each one has a specific Ka value K a1 >>>>K a2 >>K a3 When calculating the pH of a polyprotic acid, you only use the 1 st K a because all of the others are so small

5. Complete Ionization Write the steps for the complete ionization of H 2 Se

6. Complete Ionization Write the steps for the complete ionization of H 3 AsO

7. Example Calculate the pH & the [ ] of all species of a 3.0 M solution of H 3 PO 4. K a1 = 7.5 x 10 -3, K a2 = 6.2 x 10 -8, K a3 = 4.8 x 10 -13

8. Example H 3 PO 4  H + + H 2 PO 4 - K a1 = 7.5 x 10 -3 I C E

9. Example H 2 PO 4 -  H + + HPO 4 -2 K a1 = 6.2 x 10 -8 I C E

10. Example HPO 4 -2  H + + PO 4 -3 K a3 = 4.8 x 10 -13 I C E

11. Example pH = [H 3 PO 4 ] = [H 2 PO 4 - ] = [HPO 4 -2 ] = [PO 4 -3 ] = [H + ] =

12. Acid Base Properties of Salts Salts of weak acids produce basic solutions NaC 2 H 3 O 2

13. Acid Base Properties of Salts Salts of weak bases produce acidic solutions NH 4 Cl

14. Acid Base Properties of Salts Salts of strong acids & Bases produce neutral solutions NaCl

15. Calculations with salts K a xK b = K w Can find Ka or Kb with this equation On AP formula sheet

16. Example What is the pH if a 0.140M solution of NaC 2 H 3 O 2 (K a HC2H3O2 = 1.8x10 -5 ) I C E

17. Another example What is the pH of a 0.140M solution of diethylaminochloride (C 2 H 5 ) 2 NH 3 Cl. Kb (C 2 H 5 ) 2 NH 3 + = 1.3x10 -3 (C 2 H 5 ) 2 NH 3 Cl  (C 2 H 5 ) 2 NH 3 + + Cl - (C 2 H 5 ) 2 NH 3 + + H 2 O  (C 2 H 5 ) 2 NH 2 + H 3 O + I C E

18. Qualitative Predictions of pH Ka>Kb  acidic Kb>Ka  basic Ka = Kb  neutral

19. pH Predictions Predict if an aqueous solution of the following are acidic, basic, or neutral NH 4 C 2 H 3 O 2 Kb NH 4 + = 1.8x10 -5 Ka HC 2 H 3 O 2 = 1.8x10 -5

20. pH Predictions Predict if an aqueous solution of the following are acidic, basic, or neutral NH 4 CN Kb NH 4 + = 1.8x10 -5 Ka HCN= 6.2x10 -10

21. Effect of Structure of Acid Base Properties Weak acid (HF)  Stays together Strong acids  Look at electronegativity

22. Effect of Structure of Acid Base Properties