1. Water Dissociation H 2 O (l) + 59kJ ↔ H + (aq) + OH - (aq)

2. Acids and bases are really just aqueous solutions of H + or OH -, so they just shift the water dissociation equation left to a certain extent. Kw = [H + ][OH - ] = 1.0x10 -14 @25˚C If you know the [H + ] or the [OH - ] you can calculate the other one.

3. H 2 O (l) + 59kJ ↔ H + (aq) + OH - (aq) In pure water… [H + ] = [OH - ] Kw = 1.0x10 -14 = [H + ][OH - ] Kw = 1.0x10 -14 = x 2  [H + ] = 1.0x10 -7 M That’s 0.0000001M This is a very small value, especially in comparison to the H + or OH - contributed by the presence of a strong acid or base.

4. H 2 O (l) + 59kJ ↔ H + (aq) + OH - (aq) Example: What is the [OH - ] in a 0.075M HNO 3 solution? Kw = 1.0x10 -14 = [H + ][OH - ]  [OH - ] = [OH - ] = 1.3x10 -13 M

5. Ka and Kb Keq’s for weak acids or bases reacting with water HF (aq) + H 2 O (l) ↔ H 3 O + (aq) + F - (aq) Ka = NH 3(aq) + H 2 O (l) ↔ NH 4 + (aq) + OH - (aq) Kb = You can look up Ka values, but not Kb’s

6. Conjugates… HF + H 2 O ↔ H 3 O + + F - F - + H 2 O ↔ HF + OH - Ka = Kb = For Conjugates…

7. Acids react with Bases… B-L equil form when WA reacts with WB HF + NH 3 ↔ F - + NH 4 + Keq large (>1)  products favoured Keq small  reactants favoured We can only compare the strength of the acids (look up Ka values)

8. HF + NH 3 ↔ F - + NH 4 + 3. Keq = Ka(reactant acid) Ka(product acid) Keq =

9. Questions… That takes you up to #45…

10. pH pH is the “power” of Hydrogen (the exponent of the [H + ] ). Assuming it was represented as [H + ]= 10 x 4. pH = -log[H + ] 5. [H + ] = 10 -pH

11. pH = -log[H + ] and [H + ] = 10 -pH Example: What is the [OH - ] in a 0.075M HNO 3 solution? What is the pH? pH = -log(0.075) = 1.12 Note: in pH (or any logged value) numbers in front of the decimal place are not considered to be significant figures. pH = 1.12 has 2s.f. The numbers in front of the decimal are place holders and tell you how many zeros are in front of the digits.

12. pH = -log[H + ] and [H + ] = 10 -pH Example: What is the [OH - ] in a 0.075M HNO 3 solution? What is the pH? What is the pOH? pOH = -log(1.333x10 -13 ) = 12.88 Remember the pH = 1.12, what do you notice? 6. pH + pOH = 14 (@25˚C) or pH + pOH = pKw

13. What is the pOH of 3.27x10 -4 M HI? What is the [H + ] in a solution with pH= 5.52 ? What is the [OH - ] in a solution with pH = 1.72

14. If the pH = 12.825, what are the [H + ], pOH, and [OH - ] ?

15. Acid/Base Formula Sheet 1. Kw = [H + ][OH - ] = 1.0x10 -14 @25˚C 2. For conjugates, Ka x Kb = Kw 3. Keq = Kar Kap 4. pH = -log[H + ] 5. [H + ] = 10 -pH 6. pH + pOH = pKw (=14 if @25˚C) 7. There will more…

16. The pH Scale

17. Do the following questions now… Up to 56a according to the purple sheet.