1. 1 Acid-Base Titration and pH Chapter 16

2. 2 Self-Ionization of water Two water molecules produce a hydronium ion and a hydroxide ion by transfer of a proton

3. 3 Pure water Concentrations of hydronium and hydroxide ions of 1.0 x 10 -7 mol/L at 25 °C.

4. 4 Expressing concentrations Brackets indicate concentration in mol/L [H 3 O + ] means Hydronium ion concentration in moles per liter or Molar hydronium ion concentration

5. 5 Ionization constant of water 1.0 x 10 -14 M 2 or (mol/L) 2 Constant over ordinary room temperatures For pure water or dilute aqueous solutions

6. 6 Solutions Neutral [H 3 O + ]=[OH - ] Acidic [H 3 O + ]>[OH - ] Basic [H 3 O + ]<[OH - ]

7. 7 Strong bases Ionize completely in solution Molar concentration of hydroxide ions is the same as the molarity of the solution times the subscript of hydroxide. Example: A 1.0 x 10 -3 M LiOH solution has [OH - ] of 1.0 x 10 -3 M Example: A 1.0 x 10 -3 M Ca(OH) 2 solution has [OH - ] of 2.0 x 10 -3 M

8. 8 Strong Acids Ionize completely in solution Molar concentration of hydronium ions is the same as the molarity of the solution times the subscript of hydrogen. Example: A 1.0 x 10 -4 M HCl solution has [H 3 O + ] of 1.0 x 10 -4 M Example: A 1.0 x 10 -4 M H 2 SO 4 solution has [H 3 O + ] of 2.0 x 10 -4 M

9. 9 Using K w If you know the concentration of hydronium or hydroxide ions, you can use K w to find the concentration of the other ion. See page 484

10. 10 pH The negative of the common logarithm of the hydronium ion concentration

11. 11 pOH The negative of the common logarithm of the hydroxide ion concentration

12. 12 relationship

13. 13

14. 14 Discuss What is the concentration of hydronium and hydroxide ions in pure water at 25 °C? For each of the following properties, is the solution acidic or basic? [H 3 O + ] = 1.0 x 10 -3 M [OH - ] = 1.0 x 10 -4 M pH = 5.0 pH = 8.0

15. 15 Acid-Base indicators Used to obtain an approximate value for pH. Compounds whose colors are sensitive to pH. Weak acids or weak bases

16. 16 Transition interval The pH range over which an indicator changes color See page 495

17. 17 Universal indicators Use a combination of several different indicators. pH paper has been soaked in a universal indicator.

18. 18 pH meters Used to find the exact pH Measures the voltage between two electrodes placed in solution. Changes with hydronium ion concentration

19. 19 Titration The controlled addition and measurement of the amount of a solution of known concentration required to react completely with a measured amount of a solution of unknown concentration.

20. 20 Equivalence point When the two solutions used in a titration are present in chemically equivalent amounts Not always neutral

21. 21 End point The point in a titration at which an indicator changes color. Can be used to find equivalence point. If the indicator changes color at the equivalence point

22. 22 Strong acid titrated with strong base

23. 23 Weak acid titrated with strong base

24. 24 Discuss P. 503 section review 1 and 2.

25. 25 Standard solution The “known” solution Its concentration is known precisely

26. 26 Primary standard Highly purified solid comound Used to check the concentration of the known solution

27. 27 Titration process See pages 500 - 501

28. 28 Calculating the unknown concentration 1. Write the balanced chemical equation. 2. Determine the moles of the known solute. 3. Determine the moles of the unknown solute. 4. Determine the molarity of the unknown solution.

29. 29 Example A 25.00 mL sample of a solution of RbOH is neutralized by 19.22 mL of a 1.017 M solution of HBr. What is the molarity of the RbOH solution? 0.7819 M

30. 30 You try If 29.96 mL of a solution of Ba(OH) 2 requires 16.08 mL of a 2.303 M solution of HNO 3 for complete titration, what is the molarity of the Ba(OH) 2 solution? 0.6180 M

31. 31 You try You have a 0.83 M vinegar solution. You are going to titrate 20.00 mL of it with a 0.519 M NaOH solution. At what volume of added NaOH solution would you expect to see an end point? 32 mL