1. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 1 Chapter 10 Acids and Bases 10.1 Acids and Bases 10.2 Conjugate Acid-Base Pairs 10.3 Strengths of Acids and Bases 10.4 Dissociation Constants 10.5 Ionization of Water 10.6 The pH Scale 10.7 Reactions of Acids and Bases (just neutralization reactions) 10.9 Buffers

2. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 2  Arrhenius acids  Produce H + ions in water. H 2 O HCl H + (aq) + Cl – (aq)  Are electrolytes.  Have a sour taste.  Corrode metals.  React with bases to form salts and water. 10.1 Acids Examples:  Vinegar (5% acetic acid)  Citric acid (fruits)  Ascorbic acid (vitamin C)  Lactic acid (in muscles)  Phosphoric acid (Coke)

3. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 3  Arrhenius bases  Produce OH – ions in water.  Taste bitter or chalky.  Are electrolytes.  Feel soapy and slippery.  React with acids to form salts and water. Bases Examples:  Draino (NaOH)  Baking Soda (NaHCO 3 )  Bleach (NaOCl)  Ammonia (NH 3 )  Antacid

4. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 4 Comparing Acids and Bases

5. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 5 Identify each as a characteristic of an A) acid or B) base ____1. Has a sour taste. ____2. Produces OH - in aqueous solutions. ____3. Has a chalky taste. ____4. Is an electrolyte. ____5. Produces H + in aqueous solutions. Learning Check

6. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 6 Identify each as a characteristic of an A) acid or B) base A 1. Has a sour taste. B 2. Produces OH – in aqueous solutions. B 3. Has a chalky taste. A, B 4. Is an electrolyte. A 5. Produces H + in aqueous solutions. Solution

7. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 7 Names of Acids Acids with H and one nonmetal are named with the prefix hydro- and end with -ic acid. HClhydrochloric acid Acids with H and a polyatomic ion are named by changing the end of an –ate ion to -ic acid and an –ite ion to -ous acid. HClO 3 chloric acid HClO 2 chlorous acid

8. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 8 Some Acids and Their Anions

9. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 9 Name each of the following as acids: A. HBr 1. bromic acid 2. bromous acid 3. hydrobromic acid B. H 2 CO 3 1. carbonic acid 2. hydrocarbonic acid 3. carbonous acid Learning Check

10. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 10 A. HBr3. hydrobromic acid The name of an acid with H and one nonmetal begins with the prefix hydro- and ends with -ic acid. B. H 2 CO 3 1. carbonic acid An acid with H and a polyatomic ion is named by changing the end of an –ate ion to -ic acid. Solution

11. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 11  Bases with OH - ions are named as the hydroxide of the metal in the formula. NaOHsodium hydroxide KOH potassium hydroxide Ba(OH) 2 barium hydroxide Al(OH) 3 aluminum hydroxide Fe(OH) 3 iron (III) hydroxide Some Common Bases

12. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 12 Match the formulas with the names: A. ___ HNO 2 1) hydrochloric acid B. ___Ca(OH) 2 2) sulfuric acid C. ___H 2 SO 4 3) sodium hydroxide D. ___HCl4) nitrous acid E. ___NaOH5) calcium hydroxide Learning Check

13. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 13 Match the formulas with the names: A. 4 HNO 2 4) nitrous acid B. 5 Ca(OH) 2 5) calcium hydroxide C. 2 H 2 SO 4 2) sulfuric acid D. 1 HCl 1) hydrochloric acid E. 3 NaOH3) sodium hydroxide Solution

14. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 14 According to the Brønsted-Lowry theory, Acids are hydrogen ion (H + ) donors. Bases are hydrogen ion (H + ) acceptors. donor acceptor hydronium ion HCl + H 2 O H 3 O + + Cl - + - + + Johannes BrØnsted and Thomas Lowry (1923)

15. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 15 When NH 3 dissolves in water, a few NH 3 molecules react with water to form ammonium ion NH 4 + and a hydroxide ion. NH 3 + H 2 O NH 4 + (aq) + OH - (aq) acceptor donor + - + + NH 3, A Bronsted-Lowry Base

16. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 16 10.2 Conjugate Acids and Bases An acid that donates H + forms a conjugate base. A base that accepts a H + forms a conjugate acid. In an acid-base reaction, there are two conjugate acid-base pairs. acid 1 conjugate base 1 + + base 2 conjugate acid 2 HF H2OH2O H3O+H3O+ F -

17. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 17 Conjugate Acid-Base Pairs A conjugate acid-base pair is two substances related by a loss or gain of H +. + + acid 1– conjugate base 1 base 2– conjugate acid 2 HF H 2 O H3O+H3O+ F - HF, F - H 2 O, H 3 O +

18. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 18 Learning Check A. Write the conjugate base of the following: 1. HBr 2. H 2 S 3. H 2 CO 3 B. Write the conjugate acid of the following: 1. NO 2 – 2. NH 3 3. OH –

19. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 19 Solution A. Write the conjugate base of the following: 1. HBrBr - 2. H 2 SHS – 3. H 2 CO 3 HCO 3 – B. Write the conjugate acid of the following: 1. NO 2 – HNO 2 2. NH 3 NH 4 + 3. OH – H 2 O

20. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 20 Learning Check Identify the following that are acid-base conjugate pairs. 1. HNO 2, NO 2 – 2. H 2 CO 3, CO 3 2 – 3. HCl, ClO 4 – 4. HS –, H 2 S 5. NH 3, NH 4 +

21. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 21 Solution Identify the following that are acid-base conjugate pairs. 1. HNO 2, NO 2 – 4. HS –, H 2 S 5. NH 3, NH 4 +

22. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 22 Learning Check A. The conjugate base of HCO 3 – is 1. CO 3 2– 2. HCO 3 – 3. H 2 CO 3 B. The conjugate acid of HCO 3 – is 1. CO 3 2– 2. HCO 3 – 3. H 2 CO 3 C. The conjugate base of H 2 O is 1. OH – 2. H 2 O 3. H 3 O + D. The conjugate acid of H 2 O is 1. OH – 2. H 2 O 3. H 3 O +

23. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 23 Solution A. The conjugate base of HCO 3 – is 1. CO 3 2– B. The conjugate acid of HCO 3 – is 3. H 2 CO 3 C. The conjugate base of H 2 O is 1. OH – D. The conjugate acid of H 2 O is 3. H 3 O +

24. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 24 Strong acids completely ionize (100%) in aqueous solutions. HCl + H 2 O H 3 O + (aq) + Cl – (aq) (100 % ions)  Strong bases completely (100%) dissociate into ions in aqueous solutions. H 2 O NaOH Na + (aq) + OH – (aq) (100 % ions) 10.3 Strengths of Acids and Bases

25. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 25 Strong and Weak Acids In an HCl solution, the strong acid HCl dissociates 100%. A solution of the weak acid CH 3 COOH contains mostly molecules and a few ions.

26. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 26 Only a few acids are strong acids. The conjugate bases of strong acids are weak bases. Strong Acids

27. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 27 Most acids are weak acids. The conjugate bases of weak acids are strong bases. Weak Acids

28. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 28 Most bases in Groups 1A and 2A are strong bases. They include LiOH, NaOH, KOH, and Ca(OH) 2 Most other bases are weak bases. Strong Bases

29. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 29 Learning Check Identify each of the following as a strong or weak acid or base. A. HBr B. HNO 2 C. NaOH D. H 2 SO 4 E. Cu(OH) 2

30. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 30 Solution Identify each of the following as a strong or weak acid or base. A. HBrstrong acid B. HNO 2 weak acid C. NaOHstrong base D. H 2 SO 4 strong acid E. Cu(OH) 2 weak base

31. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 31 Learning Check A. Identify the stronger acid in each pair. 1. HNO 2 or H 2 S 2. HCO 3 – or HBr 3. H 3 PO 4 or H 3 O + B. Identify the strong base in each pair. 1. NO 3 – or F - 2. CO 3 2– or NO 2 – 3. OH – or H 2 O

32. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 32 Solution A. Identify the stronger acid in each pair. 1. HNO 2 2. HBr 3. H 3 O + B. Identify the stronger base in each pair. 1. F - 2. CO 3 2– 3. OH –

33. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 33 Equilibrium H 2 SO 4 + H 2 O H 3 O + + HSO 4 - strongerstrongerweaker weaker acid base acidbase CO 3 - + H 2 O HCO 3 - + OH - weaker weaker stronger stronger base acid acidbase

34. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 34 10.4 Strong Acids In water, the dissolved molecules of a strong acid are essentially all separated into ions. The concentrations of H 3 O + and the anion (A – ) are large.

35. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 35 Weak Acids In weak acids, The equilibrium favors the undissociated (molecular) form of the acid. The concentrations of the H 3 O + and the anion (A – ) are small.

36. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 36 Dissociation Constants In a weak acid, the rate of the dissociation of the acid is equal to the rate of the association. HA + H 2 O H 3 O + + A – The equilibrium expression for a weak acid is K eq = [H 3 O + ][A - ] [HA][H 2 O]

37. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 37 Acid Dissociation Constants (K a ) The [H 2 O] is large and remains unchanged. It is combined with the K eq to write the acid dissociation constant, K a. K a = K eq [H 2 O] = [H 3 O + ][A - ] [HA]

38. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 38 Writing K a for a Weak Acid Write the K a for H 2 S. 1. Write the equation for the dissociation of H 2 S. H 2 S + H 2 O H 3 O + + HS – 2. Set up the K a expression K a = [H 3 O + ][HS - ] [H 2 S]

39. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 39 Learning Check Write the K a for HCN.

40. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 40 Solution Write the K a for HCN. Write the equation for the dissociation of HCN. HCN + H 2 O H 3 O + + CN – Set up the K a expression K a = [H 3 O + ][CN – ] [HCN] Note: K a = K eq [H 2 O]

41. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 41 Acid dissociation constants Larger K a (stronger acid) Larger K b (stronger base) Smaller K a (weaker acid) Smaller K b (weaker base)

42. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 42  In water, H + is transferred from one H 2 O molecule to another.  One water molecule acts as an acid, while another acts as a base (amphiprotic). H 2 O + H 2 O H 3 O + + OH –........ : O : H + : O : H H : O : H + + : O : H –........ H H H water molecules hydronium hydroxide ion (+) ion (–) 10.5 Ionization of Water

43. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 43  In pure water, the ionization of molecules produces small, but equal quantities of H 3 O + and OH - ions. H 2 O + H 2 O H 3 O + + OH -  Molar concentrations are indicated as [H 3 O + ] and [OH - ]. [H 3 O + ] = 1.0 x 10 -7 M [OH - ] = 1.0 x 10 -7 M Pure Water is Neutral

44. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 44  Adding an acid to pure water increases the [H 3 O + ].  In acids, [H 3 O + ] exceeds 1.0 x 10 –7 M.  As [H 3 O + ] increases, [OH – ] decreases. Acidic Solutions

45. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 45  Adding a base to pure water increases the [OH – ].  In bases, [OH – ] exceeds 1.0 x 10 –7 M.  As [OH – ] increases, [H 3 O + ] decreases. Basic Solutions

46. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 46 Comparison of [H 3 O + ] and [OH – ]

47. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 47 The ion product constant, K w, for water is the product of the concentrations of the hydronium and hydroxide ions. K w = [H 3 O + ][OH – ] We can obtain the value of K w using the concentrations in pure water. K w = [1.0 x 10 –7 ][1.0 x 10 –7 ] = 1.0 x 10 –14 Ion Product of Water, K w

48. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 48 K w in Acids and Bases In neutral, acidic, and basic solutions, the K w is equal to 1.0 x 10 –14.

49. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 49 What is the [H 3 O + ] of a solution if [OH – ] is 1.0 x 10 -8 M? Rearrange the K w expression for [H 3 O + ]. K w = [H 3 O + ][OH – ] = 1.0 x 10 -14 [H 3 O + ] = 1.0 x 10 -14 [OH – ] [H 3 O + ] = 1.0 x 10 -14 = 1.0 x 10 -6 M 1.0 x 10 - 8 Calculating [H 3 O + ]

50. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 50 The [H 3 O + ] of lemon juice is 1.0 x 10 –3 M. What is the [OH – ] of the solution? 1) 1.0 x 10 3 M 2) 1.0 x 10 –11 M 3) 1.0 x 10 11 M Learning Check

51. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 51 The [H 3 O + ] of lemon juice is 1.0 x 10 –3 M. What is the [OH – ] of the solution? 2) 1.0 x 10 –11 M Rearrange the K w to solve for [OH – ] K w = [H 3 O + ][OH – ] = 1.0 x 10 –14 [OH - ] = 1.0 x 10 -14 = 1.0 x 10 –11 M 1.0 x 10 - 3 Solution

52. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 52 The [OH – ] of a solution is 5 x 10 –2 M. What is the [H 3 O + ] of the solution? 1) 2 x 10 –2 M 2) 1 x 10 2 M 3) 2 x 10 –13 M Learning Check

53. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 53 The [OH – ] of a water solution is 5 x 10 –2 M. What is the [H 3 O + ] of the solution? 3) 2 x 10 –13 M [ H 3 O + ] = 1.0 x 10 –14 5 x 10 –2 Solution

54. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 54 A. What is the [OH – ] if the [H 3 O + ] is 1 x 10 –4 M? Identify the solution as acidic, basic, or neutral. 1) 1 x 10 –6 M 2) 1 x 10 –8 M 3) 1 x 10 –10 M B. What is [H 3 O + ] if the [OH – ] is 5 x 10 –9 M? Identify the solution as acidic, basic, or neutral. 1) 1 x 10 –6 M 2) 2 x 10 –6 M 3) 2 x 10 –7 M Learning Check

55. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 55 K w = [H 3 O + ][OH – ] = 1.0 x 10 14 A. 3) [OH – ] = 1.0 x 10 –14 = 1.0 x 10 –10 1.0 x 10 –4 acidic B. 2) [H 3 O + ] = 1.0 x 10 –14 = 2 x 10 –6 5 x 10 –9 acidic Solution

56. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 56 10.6 pH Scale The pH scale:  Is used to indicate the acidity of a solution.  Has values that usually range from 0 to 14.  Indicates an acidic solution when the values are less than 7.  Indicates a neutral solution with a pH of 7.  Indicates a basic solution when the values are greater than 7.

57. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 57 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Neutral [H 3 O + ]>[OH - ] [H 3 O + ] = [OH - ] [H 3 O + ]<[OH - ] Acidic Basic pH Range

58. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 58

59. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 59 Identify each solution as 1. acidic 2. basic3. neutral A. ___ HCl with a pH = 1.5 B. ___ Pancreatic fluid [H 3 O + ] = 1 x 10 –8 M C. ___ Sprite soft drink pH = 3.0 D. ___ pH = 7.0 E. ___ [OH – ] = 3 x 10 –10 M F. ___ [H 3 O + ] = 5 x 10 –12 Learning Check

60. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 60 Identify each solution as 1. acidic 2. basic3. neutral A. 1 HCl with a pH = 1.5 B. 2 Pancreatic fluid [H 3 O + ] = 1 x 10 –8 M C. 1 Sprite soft drink pH = 3.0 D. 3 pH = 7.0 E. 1 [OH – ] = 3 x 10 –10 M F. 2 [H 3 O + ] = 5 x 10 –12 Solution

61. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 61 Testing the pH of Solutions The pH of solutions can be determined using a a) pH meter, b) pH paper, and c) indicators that have specific colors at different pHs.

62. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 62 m x = n, then log m n = x, m = 10 Ordinarily log 10 (log in calculator) log 10 100 = 2.000(10 2 = 100) log 10 1 = 0.000(10 0 = 1) log 10 0.001 = -3.000(10 -3 = 0.001) Logarithms (log)

63. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 63 1.Count the significant digits in the number (n) (log n = x ) 2.Add that same number of decimal points to the log of the number (x). Example:log 10 2.00 = 0.301 log 10 2.0 = 0.30 log 10 2 = 0.3 log 10 2.0 x 10 3 = 3.30 Logarithms (log) Sig Figs

64. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 64 pH is:  Defined as the negative log of the hydrogen ion concentration. pH = - log [H 3 O + ]  The value of the negative exponent of [H 3 O + ] for concentrations with a coefficient of 1. [H 3 O + ] =1 x 10 -4 pH = 4.0 [H 3 O + ] =1 x 10 -11 pH = 11.0 pH Scale

65. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 65 A calculator can be used to find the pH of a solution with a [H 3 O + ] of 1 x 10 -3 as follows. 1. Enter 1 x 10 -3 by pressing 1 (EE) 3 (+/–). The EE key gives an exponent of 10 and the +/– key changes the sign. 2. Press the log key to obtain log 1 x 10 -3. log (1 x 10 -3 ) = –3 3. Press the +/– key to multiply by –1. (-3) +/– = 3 Calculations of pH

66. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 66 Significant Figures in pH When expressing log values, the number of decimal places in the pH is equal to the number of significant figures in the coefficient of [H 3 O + ]. [H 3 O + ] = 1 x 10 -4 pH = 4.0 [H 3 O + ] = 1.0 x 10 -6 pH = 6.00 [H 3 O + ] = 2.4 x 10 -8 pH = 7.62

67. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 67 A. The [H 3 O + ] of tomato juice is 2 x 10 -4 M. What is the pH of the solution? 1) 4.02) 3.73) 10.3 B. The [OH - ] of a solution is 1.0 x 10 -3 M. What is the pH of the solution? 1) 3.002) 11.003) –11.00 Learning Check

68. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 68 A. 2) 3.7 pH = – log [ 2 x 10 -4 ] = 3.7 2 (EE) 4 (+/–) log (+/–) B. 2) 11.00 Use the K w to obtain [H 3 O + ] = 1.0 x 10 -11 pH = – log [1.0 x 10 - 11 ] = – 11.00 (+/–) = 11.00 Solution

69. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 69 Calculating [H 3 O + ] from pH The [H 3 O + ] can be expressed with the pH as the negative power of 10. [H 3 O + ] = 1 x 10 -pH If the pH is 3.0, the [H 3 O + ] = 1 x 10 -3 On a calculator 1. Enter the pH value 3.0 2. Use (+/–) to change sign 3.0 (+/–) = –3.0 3. Use the inverse log key (or 10 x ) to obtain the [H 3 0 + ]. =1 x 10 -3 M

70. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 70 A. What is the [H 3 O + ] of a solution with a pH of 10.0? 1) 1 x 10 -4 M2) 1 x 10 10 M 3) 1 x 10 -10 M B. What is the [H 3 O + ] of a solution with a pH of 5.7? 1) 2 x 10 - 6 M2) 5 x 10 5 M 3) 1 x 10 -5 M Learning Check

71. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 71 A. What is the [H 3 O + ] of a solution with a pH of 10.0? 3) 1 x 10 -10 M1 x 10 -pH B. What is the [H 3 O + ] of a solution with a pH of 5.7? 1) 2 x 10 - 6 M 5.7 (+/–) inv log (or 10 x ) = 2 x 10 -6 Solution

72. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 72 pOH The pOH of a solution:  Is related to the [OH - ]. Is similar to pH. pOH = – log [OH - ] Added to the pH value is equal to 14.0. pH + pOH = 14.0

73. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 73 pH and pOH The sum of the pH and pOH values is equal to 14.0 for any aqueous solution.

74. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 74 Learning Check What is the pH and the pOH of coffee if the [H 3 O + ] is 1 x 10 -5 M? 1) pH = 5.0 pOH =7.0 2) pH = 7.0 pOH = 9.0 3) pH = 5.0pOH = 9.0

75. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 75 Solution What is the pH and the pOH of coffee if the [H 3 O + ] is 1 x 10 -5 M? 3) pH = 5.0pOH = 9.0 pH = – log [1 x 10 -5 ] = –(– 5.0) = 5.0 pH + pOH = 14.0 pOH = 14.0 – pH = 14.0 – 5.0 = 9.0 or [OH - ] = 1 x 10 -9 pOH = – log [1 x 10 -9 ] = –(– 9.0) = 9.0

76. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 76 An acid such as HCl produces H 3 O + and a base such as NaOH provides OH -. HCl + H 2 OH 3 O + + Cl - NaOHNa + + OH - In a neutralization reaction, the H 3 O + and the OH - combine to form water. H 3 O + + OH - 2 H 2 O The positive ion (metal) and the negative ion (nonmetal) are the ions of a salt. 10.7 Neutralization Reactions

77. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 77 In the equation for neutralization, an acid and a base produce a salt and water. NaOH + HCl NaCl + H 2 O base acid salt water Ca(OH) 2 + 2 HCl CaCl 2 + 2H 2 O base acid salt water Neutralization Equations

78. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 78 Write the balanced equation for the neutralization of magnesium hydroxide and nitric acid. 1. Write the formulas of the acid and base. Mg(OH) 2 + HNO 3 2. Balance to give equal OH - and H +. Mg(OH) 2 + 2 HNO 3 3. Write the products (a salt and water) and balance: Mg(OH) 2 + 2HNO 3 Mg(NO 3 ) 2 + 2H 2 O Balancing Neutralization Reactions

79. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 79 Write strong acids, bases, and salts as ions. H + + Cl - + Na + + OH - Na + + Cl - + H 2 O Cross out matched ions. H + + Cl - + Na + + OH - Na + + Cl - + H 2 O Write a net ionic reaction. H + + OH - H 2 O Ionic Equations for Neutralization

80. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 80 Select the correct group of coefficients for the following neutralization equations. A. __ HCl + __ Al(OH) 3 __AlCl 3 + __ H 2 O 1) 1, 3, 3, 1 2) 3, 1, 1, 1 3) 3, 1, 1 3 B. __ Ba(OH) 2 + __H 3 PO 4 __Ba 3 (PO 4 ) 2 + __ H 2 O 1) 3, 2, 2, 2 2) 3, 2, 1, 6 3) 2, 3, 1, Learning Check

81. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 81 A. 3) 3, 1, 1 3 3HCl + 1Al(OH) 3 1AlCl 3 + 3H 2 O B. 2) 3, 2, 1, 6 3Ba(OH) 2 + 2H 3 PO 4 1Ba 3 (PO 4 ) 2 + 6H 2 O Solution

82. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 82  Antacids neutralize stomach acid (HCl). Alka-Seltzer NaHCO 3, citric acid, aspirin Chooz, TumsCaCO 3 Di-gel CaCO 3 and Mg(OH) 2 Gelusil, Maalox,Al(OH) 3 and Mg(OH) 2 Mylanta Milk of MagnesiaMg(OH) 2 Rolaids AlNa(OH) 2 CO 3 Antacids

83. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 83 Learning Check Write the neutralization reactions for stomach acid HCl and Mylanta.

84. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 84 Solution Write the neutralization reactions for stomach acid HCl and Mylanta. Mylanta: Al(OH) 3 and Mg(OH) 2 3HCl + Al(OH) 3 AlCl 3 + 3H 2 O 2HCl + Mg(OH) 2 MgCl 2 + 2H 2 O

85. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 85 When an acid or base is added to water, the pH changes drastically. A buffer solution resists a change in pH when an acid or base is added. 10.9 Buffers

86. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 86 Buffers Absorb H 3 O + or OH - from foods and cellular processes to maintain pH. Are important in the proper functioning of cells and blood. In blood maintain a pH close to 7.4. A change in the pH of the blood affects the uptake of oxygen and cellular processes. Buffers

87. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 87 A buffer solution Contains a combination of acid-base conjugate pairs. Contains a weak acid and a salt of the conjugate base of that acid. Typically has equal concentrations of a weak acid and its salt. May also contain a weak base and a salt with the conjugate acid. Components of a Buffer

88. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 88 The acetic acid/acetate buffer contains acetic acid (CH 3 COOH) and sodium acetate (CH 3 COONa). The salt produces sodium and acetate ions. CH 3 COONa CH 3 COO - + Na + The salt provides a higher concentration of the conjugate base CH 3 COO - than the weak acid. CH 3 COOH + H 2 O CH 3 COO - + H 3 O + Large amount Large amount Buffer Action

89. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 89 The function of the weak acid is to neutralize a base. The acetate ion in the product adds to the available acetate. CH 3 COOH + OH – CH 3 COO – + H 2 O Function of the Weak Acid

90. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 90 The function of the acetate ion CH 3 COO - (conjugate base) is to neutralize H 3 O + from acids. The weak acid product adds to the weak acid available. CH 3 COO - + H 3 O + CH 3 COOH + H 2 O Function of the Conjugate Base

91. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 91 The weak acid in a buffer neutralizes base. The conjugate base in the buffer neutralizes acid. The pH of the solution is maintained. Summary of Buffer Action

92. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 92 Learning Check Does each combination make a buffer solution? 1) yes2) noExplain. A. HCl and KCl B. H 2 CO 3 and NaHCO 3 C. H 3 PO 4 and NaCl D. CH 3 COOH and CH 3 COOK

93. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 93 Solution Does each combination make a buffer solution? 1) yes2) no Explain. A. HCl + KClno; HCl is a strong acid. B. H 2 CO 3 + NaHCO 3 yes; weak acid and its salt. C. H 3 PO 4 + NaCl no; NaCl does not contain a conjugate base of H 3 PO 4. D. CH 3 COOH + CH 3 COOK yes; weak acid and its salt.

94. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 94 pH of a Buffer The [H 3 O + ] in the K a expression is used to determine the pH of a buffer. Weak acid + H 2 O H 3 O + + Conjugate base K a = [H 3 O + ][conjugate base] [weak acid] [H 3 O + ] = K a x [weak acid] [conjugate base] pH = –log [H 3 O + ]

95. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 95 Calculation of Buffer pH The weak acid H 2 PO 4 - in a blood buffer H 2 PO 4 - /HPO 4 2- has K a = 6.2 x 10 -8. What is the pH of the buffer if it is 0.20 M in both H 2 PO 4 - and HPO 4 2- ? [H 3 O + ] = K a x [H 2 PO 4 - ] [HPO 4 2- ] [H 3 O + ] = 6.2 x 10 -8 x [0.20 M] = 6.2 x 10 -8 [0.20 M] pH = –log [6.2 x 10 -8 ] = 7.17

96. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 96 Learning Check What is the pH of a H 2 CO 3 buffer that is 0.20 M H 2 CO 3 and 0.10 M HCO 3 - ? K a (H 2 CO 3 ) = 4.3 x 10 -7

97. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 97 Solution What is the pH of a H 2 CO 3 buffer that is 0.20 M H 2 CO 3 and 0.10 M HCO 3 - ? K a (H 2 CO 3 ) = 4.3 x 10 -7 [H 3 O + ] = K a x [H 2 CO 3 ] [HCO 3 - ] [H 3 O + ] = 4.3 x 10 -7 x [0.20 M] = 8.6 x 10 -7 [0.10 M] pH = –log [8.6 x 10 -7 ] = 6.07