1. Part II

2. Polyprotic acid H 2 CO 3 H + + HCO 3 - Ka 1 = 4.3 x 10 -7 H 2 CO 3 H + + HCO 3 - Ka 1 = 4.3 x 10 -7 HCO 3 - H + + CO 3 -2 Ka 2 = 4.3 x 10 -10 HCO 3 - H + + CO 3 -2 Ka 2 = 4.3 x 10 -10 Base in first step is acid in second. Base in first step is acid in second. In calculations we can normally ignore the second dissociation. In calculations we can normally ignore the second dissociation.

3. Sulfuric acid is special In first step it is a strong acid. In first step it is a strong acid. Ka 2 = 1.2 x 10 -2 Ka 2 = 1.2 x 10 -2 Calculate the concentrations in a 2.0 M solution of H 2 SO 4 Calculate the concentrations in a 2.0 M solution of H 2 SO 4 Calculate the concentrations in a 2.0 x 10 -3 M solution of H 2 SO 4 Calculate the concentrations in a 2.0 x 10 -3 M solution of H 2 SO 4

4. Salts as acids an bases Salts are ionic compounds. Salts are ionic compounds. Salts of the cation of strong bases and the anion of strong acids are neutral. Salts of the cation of strong bases and the anion of strong acids are neutral. for example NaCl, KNO 3 for example NaCl, KNO 3 There is no equilibrium for strong acids and bases. There is no equilibrium for strong acids and bases. We ignore the reverse reaction. We ignore the reverse reaction.

5. Basic Salts If the anion of a salt is the conjugate base of a weak acid - basic solution. If the anion of a salt is the conjugate base of a weak acid - basic solution. In an aqueous solution of NaF In an aqueous solution of NaF The major species are Na +, F -, and H 2 O The major species are Na +, F -, and H 2 O F - + H 2 O HF + OH - F - + H 2 O HF + OH - K b =[HF][OH - ] [F - ] K b =[HF][OH - ] [F - ] but Ka = [H + ][F - ] [HF] but Ka = [H + ][F - ] [HF]

6. Basic Salts K a x K b = [HF][OH - ]x [H + ][F - ] [F - ] [HF] K a x K b = [HF][OH - ]x [H + ][F - ] [F - ] [HF]

7. Basic Salts K a x K b = [HF][OH - ]x [H + ][F - ] [F - ] [HF] K a x K b = [HF][OH - ]x [H + ][F - ] [F - ] [HF]

8. Basic Salts K a x K b = [HF][OH - ]x [H + ][F - ] [F - ] [HF] K a x K b = [HF][OH - ]x [H + ][F - ] [F - ] [HF]

9. Basic Salts K a x K b = [HF][OH - ]x [H + ][F - ] [F - ] [HF] K a x K b = [HF][OH - ]x [H + ][F - ] [F - ] [HF] K a x K b =[OH - ] [H + ] K a x K b =[OH - ] [H + ]

10. Basic Salts K a x K b = [HF][OH - ]x [H + ][F - ] [F - ] [HF] K a x K b = [HF][OH - ]x [H + ][F - ] [F - ] [HF] K a x K b =[OH - ] [H + ] K a x K b =[OH - ] [H + ] K a x K b = K W K a x K b = K W

11. K a tells us K b The anion of a weak acid is a weak base. The anion of a weak acid is a weak base. Calculate the pH of a solution of 1.00 M NaCN. K a of HCN is 6.2 x 10 -10 Calculate the pH of a solution of 1.00 M NaCN. K a of HCN is 6.2 x 10 -10 The CN - ion competes with OH - for the H + The CN - ion competes with OH - for the H +

12. Acidic salts A salt with the cation of a weak base and the anion of a strong acid will be basic. A salt with the cation of a weak base and the anion of a strong acid will be basic. The same development as bases leads to The same development as bases leads to K a x K b = K W K a x K b = K W Calculate the pH of a solution of 0.40 M NH 4 Cl (the K b of NH 3 1.8 x 10 -5 ). Calculate the pH of a solution of 0.40 M NH 4 Cl (the K b of NH 3 1.8 x 10 -5 ). Other acidic salts are those of highly charged metal ions. Other acidic salts are those of highly charged metal ions.

13. Anion of weak acid, cation of weak base K a > K b acidic K a > K b acidic K a < K b basic K a < K b basic K a = K b Neutral K a = K b Neutral

14. Structure and Acid base Properties Any molecule with an H in it is a potential acid. Any molecule with an H in it is a potential acid. The stronger the X-H bond the less acidic (compare bond dissociation energies). The stronger the X-H bond the less acidic (compare bond dissociation energies). The more polar the X-H bond the stronger the acid (use electronegativities). The more polar the X-H bond the stronger the acid (use electronegativities). The more polar H-O-X bond -stronger acid. The more polar H-O-X bond -stronger acid.

15. Strength of oxyacids The more oxygen hooked to the central atom, the more acidic the hydrogen. The more oxygen hooked to the central atom, the more acidic the hydrogen. HClO 4 > HClO 3 > HClO 2 > HClO HClO 4 > HClO 3 > HClO 2 > HClO Remember that the H is attached to an oxygen atom. Remember that the H is attached to an oxygen atom. The oxygens are electronegative The oxygens are electronegative

16. Strength of oxyacids Electron Density ClOH

17. Strength of oxyacids Electron Density ClOHO

18. Strength of oxyacids ClOH O O Electron Density

19. Strength of oxyacids ClOH O O O Electron Density

20. Hydrated metals Highly charged metal ions pull the electrons of surrounding water molecules toward them. Highly charged metal ions pull the electrons of surrounding water molecules toward them. Make it easier for H + to come off. Make it easier for H + to come off. Al +3 O H H

21. Acid-Base Properties of Oxides Non-metal oxides dissolved in water can make acids. Non-metal oxides dissolved in water can make acids. SO 3 (g) + H 2 O(l) H 2 SO 4 (aq) SO 3 (g) + H 2 O(l) H 2 SO 4 (aq) Ionic oxides dissolve in water to produce bases. Ionic oxides dissolve in water to produce bases. CaO(s) + H 2 O(l) Ca(OH) 2 (aq) CaO(s) + H 2 O(l) Ca(OH) 2 (aq)

22. Lewis Acids and Bases Most general definition. Most general definition. Acids are electron pair acceptors. Acids are electron pair acceptors. Bases are electron pair donors. Bases are electron pair donors. BF F F :N:N H H H

23. Lewis Acids and Bases Boron triflouride wants more electrons. Boron triflouride wants more electrons. BF F F :N:N H H H

24. Lewis Acids and Bases Boron triflouride wants more electrons. Boron triflouride wants more electrons. BF 3 is Lewis base NH 3 is a Lewis Acid. BF 3 is Lewis base NH 3 is a Lewis Acid. B F F F N H H H

25. Lewis Acids and Bases Al +3 ( ) H H O Al ( ) 6 H H O + 6 +3