1. 1 Acids, Bases and Salts Chapter 15 Hein and Arena Eugene Passer Chemistry Department Bronx Community College © John Wiley and Sons, Inc Version 2.0 12 th Edition

2. 2 Chapter Outline 15.1 Acids and BasesAcids and Bases 15.2 Reactions of AcidsReactions of Acids 15.3 Reactions of BasesReactions of Bases 15.10 NeutralizationNeutralization 15.11 Writing Net Ionic EquationsWriting Net IonicEquations 15.4 SaltsSalts 15.5 Electrolytes and NonelectrolytesElectrolytes andNonelectrolytes 15.9 Introduction to pHIntroduction to pH 15.12 Acid RainAcid Rain 15.13 ColloidsColloids 15.6 Dissociation and Ionization of ElectrolytesDissociation and Ionizationof Electrolytes 15.7 Strong and Weak ElectrolytesStrong and WeakElectrolytes 15.8 Ionization of WaterIonization of Water 15.14 Properties of ColloidsProperties of Colloids

3. 3 15.1 Acids and Bases

4. 4 Acid Properties sour taste change the color of litmus from blue to red react with –metals such as zinc and magnesium to produce hydrogen gas –hydroxide bases to produce water and an ionic compound (salt) –carbonates to produce carbon dioxide. These properties are due to the release of hydrogen ions, H +, into water solution.

5. 5 Base Properties bitter or caustic taste a slippery, soapy feeling. the ability to change litmus red to blue the ability to interact with acids

6. 6 Svante Arrhenius was a Swedish scientist who lived from 1859-1927. In 1884 he advanced a theory of acids and bases.

7. 7 An Arrhenius acid “is a hydrogen- containing substance that dissociates to produce hydrogen ions.” HA → H + + A - acid

8. 8 An Arrhenius base is a hydroxide- containing substance that dissociates to produce hydroxide ions in aqueous solution. MOH → M + (aq) + OH - (aq) base

9. 9 An Arrhenius acid solution contains an excess of H + ions. An Arrhenius base solution contains an excess of OH - ions.

10. 10 J.N. Bronsted (1897-1947) was a Danish chemist and T. M. Lowry (1847-1936) was an English chemist. In 1923 they advanced their theory of acids and bases.

11. 11 A Bronsted-Lowry acid is a proton (H + ) donor. A Bronsted-Lowry base is a proton (H + ) acceptor.

12. 12 HCl + H 2 O(l) → H 3 O + (aq) + Cl - (aq) proton acceptor Bronsted-Lowry Base proton donor Bronsted-Lowry Acid

13. 13 hydrogen ion does not exist in water hydrogen ion combines with water a hydronium ion is formed

14. 14 HCl(g) → Cl - (aq) baseacid Conjugate acid-base pairs differ by a proton. When an acid donates a proton it becomes the conjugate base.

15. 15 Conjugate acid-base pairs differ by a proton. When a base accepts a proton it becomes the conjugate acid. H 3 O + (aq)H 2 O (l) → acidbase

16. 16 Conjugate acid-base pairs differ by a proton. baseacid HCl(g)+ → Cl - (aq)+H 3 O + (aq)H 2 O (l) acidbase

17. 17 Conjugate acid-base pairs differ by a proton. baseacid HCl(g)+ → Cl - (aq)+H 3 O + (aq)H 2 O (l) acidbase

18. 18 A Lewis acid is an electron-pair acceptor. A Lewis base is an electron-pair donor.

19. 19

20. 20 15.3 Reactions of Bases

21. 21 HBr(aq) + KOH(aq) → KBr(aq) + H 2 O(l) Reaction with Acids The reaction of an acid with a base is called a neutralization reaction. In an aqueous solution the products are a salt and water: 2HNO 3 (aq) + Ca(OH) 2 (aq) → Ca(NO 3 ) 2 (aq) + 2H 2 O(l) acidbasesalt acidbasesalt

22. 22 15.4 Salts

23. 23 Salts can be considered compounds derived from acids and bases. They consist of positive metal or ammonium ions combined with nonmetal ions (OH - and O 2- excluded). Chemists use the terms ionic compound and salt interchangeably. Salts are usually crystalline and have high melting and boiling points.

24. 24 NaOHHCl NaCl base acid salt The positive ion of the salt is derived from the base. The negative ion of the salt is derived from the acid. Salt Formation

25. 25 15.5 Electrolytes and Nonelectrolytes

26. 26 Electrolytes are substances whose aqueous solutions conduct electricity. Nonelectrolytes are substances whose aqueous solutions do not conduct electricity. Electrolytes are capable of producing ions in solution. Nonelectrolytes are not capable of producing ions in solution.

27. 27 Classes of compounds that are electrolytes are: –acids –bases –salts –solutions of oxides that form an acid or a base

28. 28

29. 29 15.6 Dissociation and Ionization of Electrolytes

30. 30 Dissociation is the process by which the ions of a salt separate as the salt dissolves.

31. 31 In a crystal of sodium chloride positive sodium ions are bonded to negative chloride ions. 15.2

32. 32 In aqueous solution the sodium and chloride ions dissociate from each other. 15.2

33. 33 In aqueous solution the sodium and chloride ions dissociate from each other. 15.2

34. 34 Na + and Cl - ions hydrate with H 2 O molecules. 15.2

35. 35 Acetic acid ionizes in water to form acetate ion and hydronium ion. HC 2 H 3 O 2 + H 2 O H 3 O + + C 2 H 3 O 2 - → → Lewis acid Lewis baseLewis acid Lewis base HC 3 H 3 O 2 H + + C 2 H 3 O 2 - → → The equation can be written more simply as: In the absence of water, ionization reactions do not occur.

36. 36 15.7 Strong and Weak Electrolytes

37. 37 Strong Electrolyte An electrolyte that is essentially 100% ionized in aqueous solution. Weak Electrolyte An electrolyte that is ionized to a small extent in aqueous solution.

38. 38 Most salts are strong electrolytes Strong acids and bases (highly ionized) are strong electrolytes. Weak acids and bases (slightly ionized) are weak electrolytes.

39. 39 HCl Solution HC 2 H 3 O 2 Solution Strong AcidWeak Acid1% ionized 100% ionized 15.3

40. 40 HC 2 H 3 O 2 (aq) → H + (aq) + C 2 H 3 O 2 (aq) → → Both the ionized and unionized forms of a weak electrolyte are present in aqueous solution. ionizedunionized

41. 41 HNO 3 (aq) → H + (aq) + NO 3 (aq) HNO 3, a strong acid, is 100 % dissociated. HNO 2 (aq) → H + (aq) + NO 2 (aq) → → HNO 2, a weak acid, is only slightly ionized.

42. 42

43. 43 Electrolytes yield two or more ions per formula unit upon dissociation. NaOH → Na + (aq) + OH - (aq) Na 2 SO 4 → 2Na + (aq) + SO 4 - (aq) two ions in solution per formula unit Fe 2 (SO 4 ) 3 → 2Fe 3+ (aq) + 3SO 4 - (aq) three ions in solution per formula unit five ions in solution per formula unit

44. 44 Electrolytes yield two or more moles of ions per mole of electrolyte upon dissociation. NaOH → Na + (aq) + OH - (aq) 1 mole Na 2 SO 4 → 2Na + (aq) + SO 4 - (aq) 1 mole2 moles1 mole Fe 2 (SO 4 ) 3 → 2Fe 3+ (aq) + 3SO 4 - (aq) 1 mole2 moles3 moles

45. 45 Colligative Properties of Electrolyte Solutions

46. 46 15.8 Ionization of Water

47. 47 Water ionizes slightly. acidbaseacidbase H 2 O + H 2 O → H 3 O + + OH - → → hydronium ion hydroxide ion H 2 O → H + + OH - → → Water ionization can be expressed more simply as: [H 3 O + ] or [H + ] = 1.0 x 10 -7 mol/L [OH - ] = 1.0 x 10 -7 mol/L Two out of every 1 billion water molecules are ionized.

48. 48 15.9 Introduction to pH

49. 49 pH is the negative logarithm of the hydrogen ion concentration. pH = -log[H + ]

50. 50 Calculation of pH

51. 51 pH = -log[H + ] [H + ] = 1 x 10 -5 when this number is exactly 1 pH = this number without the minus sign. pH = 5

52. 52 pH = -log[H + ] [H + ] = 2 x 10 -5 when this number is between 1 and 10 The number of decimal places of a logarithm is equal to the number of significant figures in the original number. pH is between this number and the next lower number (between 4 and 5). one significant figure ph = 4.7 one decimal place

53. 53 What is the pH of a solution with an [H + ] of 1.0 x 10 -11 ? pH = - log(1.0 x 10 -11 ) pH = 11.00 2 decimal places 2 significant figures

54. 54 What is the pH of a solution with an [H + ] of 6.0 x 10 -4 ? pH = - log[H + ] = -(3.22) = 3.22 2 decimal places 2 significant figures log[H + ] = log (6.0 x 10 -4 ) = -3.22

55. 55 What is the pH of a solution with an [H + ] of 5.47 x 10 -8 ? pH = - log[H + ] = -(7.262) = 7.262 3 decimal places 3 significant figures log[H + ] = log(5.47 x 10 -8 ) = -7.262

56. 56 The pH scale of Acidity and Basicity 15.4

57. 57 15.10 Neutralization

58. 58 Neutralization The reaction of an acid and a base to form a salt and water. HCl(aq) + KOH(aq) → KCl(aq) + H 2 O(l) acidbasesalt

59. 59 Titrations

60. 60 Titration The process of measuring the volume of one reagent required to react with a measured mass or volume of another reagent.

61. 61 42.00 mL of 0.150 M NaOH solution is required to neutralize 50.00 mL of hydrochloric acid solution. What is the molarity of the acid solution? The equation for the reaction is HCl(aq) + NaOH(aq) → NaCl(aq) + H 2 O(l) acidbasesalt Convert mL of NaOH to liters of NaOH The unit of volume when using molarity is liters. Calculate the moles of NaOH that react. Calculate the liters of NaOH that react.

62. 62 42.00 mL of 0.150 M NaOH solution is required to neutralize 50.00 mL of hydrochloric acid solution. What is the molarity of the acid solution. The equation for the reaction is HCl(aq) + NaOH(aq) → NaCl(aq) + H 2 O(l) acidbasesalt The mole ratio of HCl to NaOH is 1:1The moles of NaOH that react equals the moles of HCl that react. 0.00630 mol NaOH react.0.00630 mol HCl react. The molarity of the HCl solution is

63. 63 15.12 Acid Rain

64. 64 Acid rain is any atmospheric precipitation that is more acidic than usual. The increase in acidity might be from natural or industrial sources.

65. 65 The pH of rain is lower in the eastern US and higher in the western US. CO 2 (g) + H 2 O(l) H 2 CO 3 (aq) H + + HCO 3 → → → → Unpolluted rain has a pH of 5.6 because of carbonic acid formation in the atmosphere.

66. 66 2.transportation of these oxides into the atmosphere 3.chemical reactions between the oxides and water forming sulfuric acid (H 2 SO 4 ) and nitric acid (HNO 3 ) 4.rain or snow, which carries the acids to the ground Process of Acid Rain Formation 1.emission of nitrogen and sulfur oxides into the air From the burning of fossil fuels.

67. 67 2.aluminum is leached from the soil into lakes and adversely affects fish gills. 3.the waxy protective coat on plants is dissolved making them vulnerable to bacteria and fungal attack Effects of Acid Rain 1.freshwater plants and animals decline significantly when rain is acidic

68. 68 5.it reduces the durability of paint and promotes the deterioration of paper, leather and cloth Effects of Acid Rain 4.it is responsible for extensive and continuing damage to buildings, monuments and statues