What is pH?

1. What is pH? • Tells us the relative quantity of H+ ions (or the acidity) in solution. • The greater the [H+] the lower the pH.

2. pH Values of Common Liquids

3. H+ and OH- in Pure Water Self Ionization of Water: small quantity of water molecules in a sample will self ionize. Results in small, but equal [H+] and [OH-] Concentration of these ions is 1 x 10-7 M (pH = 7) Reversible reaction that is at equilibrium. H2O H+ + OH- [H+] = [OH-] H+ OH- http://youtu.be/kW-Zk4zABzw

4. When Acid is Added to Water Increases the H+ concentration As H+ increases, OH- decreases [H+] > [OH-] H+ OH-

5. When Base is Added to Water Increases OH- concentration When OH- increases, H+ decreases [OH] > [H+] OH- H+

6. pH Scale 0 1 2 3 4 5 6 7 8 910 11 12 13 14 Neutral [H+]>[OH-][H+] = [OH-][OH-]>[H+] Acidic Basic

8. Important Summary • Acidic: [H+] > [OH-] • Basic: [H+] < [OH-] • Neutral: [H+] = [OH-]

9. Pretty Hydrangeas • The color of hydrangea flowers depends on the pH of the soil.

10. Calculating pH pH = - log [H+] From the French pouvoir hydrogene (“hydrogen power” or power of hydrogen)

11. [H+] pH 1 x 10-5 M 5 1 x 10-9 M 9 1 x 10-11M 11 11

12. If the [H+] is 0.000001 M, what is the pH? pH = 6 • If the [H+] is 0.01M, what is the pH? pH = 2

13. If the pH is 10, what is the [H+]? [H+] = 1 x 10-10 M • If the pH is 4, what is the [H+]? [H+] = 1 x 10-4 M

14. Calculating pOH • What if you are given the concentration of a base? • Ex: .000001M LiOH You need to find the pOH!!

15. pOH pOH = -log [OH-] Ex: .000001M LiOH = 1 x 10-6 pOH = 6 Ex: .0001M NaOH = 1 x 10-4 pOH = 4

16. How can you find pH of a Base? • Easy!!! pH + pOH = 14 Ex: .000001M LiOH = 1 x 10-6 pOH = 6 pH = 8 Ex: .0001M NaOH = 1 x 10-4 pOH = 4 pH = 10

17. Kw or Equilibrium Constant for Water If you know the concentration of one ion you can find the other! [H+] x [OH-] = 1 x 10-14 • If [H+] is .001M what is the [OH-]? [1 x 10-3] x [OH-] = 1 x 10-14 [OH-] = 1 x 10-11

18. Everything keeps adding up to 14!! What’s up with that?

19. Let’s Try It You have a .001 HCl solution. Find: [H+], [OH-], pH, pOH

20. Let’s Try It You have a .000000001M NaOH solution. Find: [H+], [OH-], pH, pOH

21. Equation Summary pH = -log [H+ ] pOH = -log [OH- ] [H+ ] = 10-pH [OH- ] = 10-pOH pH + pOH = 14 [H+ ] x [OH- ] = 1x10-14 Acidic solution: pH < 7 pOH > 7 Neutral solution: pH = 7 pOH = 7 Basic solution: pH > 7 pOH < 7

22. Let’s Practice • A solution with a pH of 2.0 has a hydronium ion concentration ten times greater than a solution with a pH of (1) 1      (2) 3 (3) 0.20    (4) 20

23. Which statement correctly describes a solution with a pH of 9? (1) It has a higher concentration of H3O+ than OH– and causes litmus to turn blue. (2) It has a higher concentration of OH–  than  H3O+  and causes litmus to turn blue. (3) It has a higher concentration of H3O+  than  OH–  and causes methyl orange to turn yellow. (4) It has a higher concentration of OH–  than  H3O+  and causes methyl orange to turn red.

24. What is the pH of a solution that has a hydronium ion concentration 100 times greater than a solution with a pH of 4? (1) 5 (2) 3 (3) 2  (4) 6

25. Solution A has a pH of 3 and solution Z has a pH of 6. How many times greater is thehydronium ion concentration in solution A than the hydronium ion concentration in solution Z? (1) 100 (2) 3 (3) 2   (4) 1000

26. When the pH of a solution changes from a pH of 5 to a pH of 3, the hydronium ion concentration is 1). 0.01 of the original content 2). 0.1 of the original content 3). 10 times the original content 4). 100 times the original content

27. As the pH of a solution is changed from 3 to 6, the concentration of hydronium ions (1) increases by a factor of 3 (2) increases by a factor of 1000 (3) decreases by a factor of 3 (4) decreases by a factor of 1000

28. Honors Questions If the pH of a solution is 3.25 find the pOH, [H+], and [OH-]. If .065 mole of KOH is placed in 20 liters of water, what is the resulting pH?

29. Crash Course pH and pOH • http://www.youtube.com/watch?v=LS67vS10O5Y&safe=active

30. Acid Rain (Not to be confused with “Chocolate Rain”)

31. Acid Rain • Unpolluted rain has a pH of 5.6 • It is naturally acidic due to the gases in the air that dissolve in it.

32. Acid Rain • Rain with a pH below 5.6 is “acid rain“

34. pH of Rainwateracross United States in 2001

35. Sources of Acid Rain

36. Sources of Acid Rain Power stations Oil refineries Coal with high S content Car and truck emissions Bacterial decomposition, and lightning hitting N2

37. CO2 in the air forms carbonic acid CO2 + H2O H2CO3 This increases the [H+]of rain H2CO3 H+ (aq) + HCO3-(aq) Reactions with oxygen in air form SO3 2SO2 + O2 2 SO3 Reactions with water in air form acids SO3 + H2O H2SO4 sulfuric acid NO + H2O HNO2 nitrous acid HNO2 + H2O HNO3 nitric acid

38. Effects of Acid Rain

39. Effects of Acid Rain • Leaches heavy metals like Al from soil, which kills fish • Fish kills in spring from runoff due to accumulation of large amounts of acid in snow • Prevents shellfish from building strong shells • Dissolves waxy coatings that protect leaves from bacteria • Corrodes metals, textiles, paper and leather

40. Honors: pH and pOH game • http://www.quia.com/rr/4051.html

41. Acid Rain Destroys National Monuments http://news.discovery.com/videos/earth-acid-rain-eating-washington-dc.html Global Warming: CO2 and Ocean Acidity http://planetgreen.discovery.com/videos/blue-august-acid-in-the-water.html

42. Acid Rain Site produced by EPA • http://www.epa.gov/acidrain/education/site_kids/ • EPA Website Detailing Acid Rain Causes and Effects as well as Legislation • http://www.epa.gov/acidrain/