2. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter Presentation Bellringers Transparencies Standardized Test Prep Math Skills Visual Concepts Resources

3. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Acids, Bases, and Salts Chapter 8 Table of Contents Section 1 Acids, Bases, and pH Section 2 Reactions of Acids with Bases Section 3 Acids, Bases, and Salts in the Home

4. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Acids, Bases, and pH Objectives Describe the ionization of strong acids in water and the dissociation of strong bases in water. Distinguish between solutions of weak acids or bases and solutions of strong acids or bases. Relate pH to the concentration of hydronium ions and hydroxide ions in a solution. Chapter 8

5. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Bellringer Even if you have not studied acids and bases before, you may already know something about them. To tap into this knowledge, identify whether the following are acids or bases. (Hint: Acids and bases have chemical properties that are very different.) 1. Vinegar 2. Baking soda 3. Soap 4. Orange juice 5. Antacid tablets 6. Given your categorization of these substances, name one property of acids. 7. Given your categorization of these substances, name one property of bases. Section 1 Acids, Bases, and pH Chapter 8

6. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu What Are Acids? An acid is a compound that dissolves in water to increase the number of hydronium ions, H 3 O +, in solution. An indicator is a compound that can reversibly change color depending on the pH of the solution or other chemical change. An indicator can tell you whether a substance is acidic or basic. For example, acids turn blue litmus paper red. Section 1 Acids, Bases, and pH Chapter 8

7. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Acids Section 1 Acids, Bases, and pH Chapter 8

8. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu What Are Acids? continued An electrolyte is a substance that dissolves in water to give a solution that conducts an electric current. Section 1 Acids, Bases, and pH Chapter 8 Strong acids ionize completely. Strong acids are strong electrolytes. Weak acids do not ionize completely. Weak acids are weak electrolytes.

9. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu What Are Acids? continued Some examples of strong acids: Hydrochloric acid, HCl present in your stomach Sulfuric acid, H 2 SO 4 car batteries; the most-used industrial chemical Nitric acid, HNO 3 used in manufacturing fertilizers and explosives Some examples of weak acids: Acetic acid, CH 3 COOH the acid in vinegar Formic acid, HCOOH the acid in stinging ants Citric acid, H 3 C 6 H 5 O 7 the acid in citrus fruits Section 1 Acids, Bases, and pH Chapter 8

10. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Common Acids Section 1 Acids, Bases, and pH Chapter 8

11. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu What Are Bases? A base is a compound that dissolves in water to increase the number of hydroxide ions, OH –, in solution. Strong bases are ionic compounds that contain a metal ion and a hydroxide ion, for example, NaOH, sodium hydroxide. Weak bases, such as ammonia, NH 3, ionize incompletely in water to form hydroxide ions. Section 1 Acids, Bases, and pH Chapter 8

12. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Strength and Weakness of Acids and Bases Section 1 Acids, Bases, and pH Chapter 8

13. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu What is pH? pH is a value used to express the acidity or basicity of a solution. pH values correspond to the concentration of hydronium ions. They also indicate hydroxide ion concentration. A neutral solution, such as pure water, has a pH of 7. An acidic solution has a pH of less than 7. A basic solution has a pH of greater than 7. Section 1 Acids, Bases, and pH Chapter 8

14. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu pH Section 1 Acids, Bases, and pH Chapter 8

15. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu pH Scale Section 1 Acids, Bases, and pH Chapter 8

16. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu What is pH? continued The concentration of a strong acid allows you to calculate pH. When the H 3 O + concentration of a solution can be written as a power of 10, the pH is the negative of the power of 10 used to describe the concentration. Examples: The pH of pure water is 7, so the concentration of H 3 O + in water is 10 –7 M. The pH of apple juice is about 3, so the concentration of H 3 O + in water is 10 –3 M. Section 1 Acids, Bases, and pH Chapter 8

17. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Math Skills Determining pH Determine the pH of a 0.0001 M solution of the strong acid HCl dissolved in water. 1. List the given and unknown values. Given: concentration of HCl in solution = 0.0001 M Unknown: pH 2. Determine the molar concentration of hydroxide ions. HCl is completely ionized into H 3 O + and Cl – ions. concentration of H 3 O + = concentration of HCl = 0.0001 M = 1  10 –4 M Section 1 Acids, Bases, and pH Chapter 8

18. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 3. Convert the H 3 O + concentration to pH. concentration of H 3 O + ions = 1  10 –4 M pH = –(–4) = 4 Math Skills, continued Section 1 Acids, Bases, and pH Chapter 8

19. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu What is pH? continued Small differences in pH mean large differences in acidity. Example: the pH of apple juice differs from the pH of coffee by two units, so apple juice is 10 2, or 100, times more acidic than coffee. pH can be measured in more than one way. A more accurate method than the use of indicators is to use an electronic pH meter, which can measure pH very precisely. Section 1 Acids, Bases, and pH Chapter 8

20. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Reactions of Acids with Bases Objectives Write ionic equations for neutralization reactions. Identify the products of a neutralization reaction. Describe the composition of a salt. Chapter 8

21. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Reactions of Acids with Bases Bellringer You have learned that acids and bases dissociate into ions in solution. The characteristic ions are the hydronium, or H 3 O +, ion for acids and the hydroxide, or OH –, ion for bases. Below are listed several reactions between acids and bases. From what you know about reactions, acids, and bases, predict what the products of the following reactions will be. 1. HCl(aq) + NaOH(aq)  ______ + H 2 O(l) 2. HCl(aq) + KOH(aq)  KCl(aq) + ______ 3. HNO 3 (aq) + KOH(aq)  ______ + ______ 4. H 2 SO 4 (aq) + Ca(OH) 2 (aq)  ______ + ______ 5. HBr(aq) + AgOH(aq)  ______ + ______ 6. HClO 4 (aq) + NaOH(aq)  ______ + ______ 7. 2HNO 3 (aq) + Ba(OH) 2 (aq)  ______ + ______ 8. H 2 SO 4 (aq) + 2NH 4 OH(aq)  ______ + ______ Chapter 8

22. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Reactions of Acids with Bases Acid-Base Reactions A reaction between an acid and a base is a neutralization reaction. Neutralization is an ionic reaction. Example: A strong acid such as HCl ionizes completely in solution: HCl + H 2 O  Cl – + H 3 O + A strong base such as NaOH ionizes completely in solution: NaOH  Na + + OH – The total neutralization reaction is the following: Cl – + H 3 O + + Na + + OH –  Na + + Cl – + 2H 2 O Chapter 8

23. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Neutralization Reaction Section 2 Reactions of Acids with Bases Chapter 8

24. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Reactions of Acids with Bases Acid-Base Reactions, continued Neutralization reactions form water and a salt. A salt is an ionic compound that forms when a metal atom or a positive radical replaces the hydrogen of an acid. Not all neutralization reactions produce neutral solutions. The final pH of the solution depends on: the amounts of acid and base that are combined whether the acid and base are strong or weak Chapter 8

25. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Salt Section 2 Reactions of Acids with Bases Chapter 8

26. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Reactions of Acids with Bases Acid-Base Reactions, continued A titration is a neutralization reaction in which the known concentration of one solution is used to determine the unknown concentration of another solution. When the amounts of acid and base added are equal, an equivalence point will be reached. The equivalence point will be at pH 7 for the titration of a strong acid with a strong base, but if a weak acid or base is involved, the equivalence point will not be neutral. Chapter 8

27. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Titration Section 2 Reactions of Acids with Bases Chapter 8

28. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Equivalence and End Points Section 2 Reactions of Acids with Bases Chapter 8

29. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Reactions of Acids with Bases Salts To a chemist, a salt can be almost any combination of cations and anions. Common table salt contains sodium chloride, NaCl, which is a salt that is formed from the reaction of hydrochloric acid with sodium hydroxide. Salts are useful substances, and are all around us. Examples: sodium hydrogen carbonate, baking soda silver bromide and silver iodide, in photographic film barium sulfate, sometimes used in taking X rays calcium carbonate, in chalk, limestone, and marble Chapter 8

30. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Acids, Bases, and Salts in the Home Objectives Describe the chemical structures of soaps and detergents and explain how they work. Describe the chemical composition of bleach and its uses. Describe how an antacid reduces stomach acid. Identify acidic and basic household products and their uses. Chapter 8

31. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Acids, Bases, and Salts in the Home Bellringer Many acids, bases, and salts are used daily in our homes. Based on what you know about the properties of acids, bases, and salts, answer the following items. 1. Some green apples are particularly sour. Is this likely to be due to an excess of acid or base? 2. Baking soda reacts with vinegar. Is baking soda an acid or a base? 3. What products besides carbon dioxide remain after vinegar and baking soda react completely? 4. Given that one approach to an upset stomach is to take an antacid, are the chemicals secreted into the stomach for digestion likely to be acids or bases? 5. Drain cleaners that contain lye react with fatty acids in clogs. Given that, are drain cleaners that contain lye acids or bases? 6. Why does the clog dissolve after the reaction of the fatty acids with lye? 7. Many common window cleaners contain ammonia, a base. Given that, is most dirt on window slightly acidic or slightly basic? Chapter 8

32. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Acids, Bases, and Salts in the Home Cleaning Products Soap improves water’s ability to clean because it can dissolve in both oil and in water. This allows oil and water to form an emulsion that can be washed away by rinsing. Soaps are salts of sodium or potassium and fatty acids. When soap combines with certain cations, such as Mg 2+, Ca 2+, and Fe 3+, it can form soap scum. Detergents have replaced soap in many applications because they do not form scum. Chapter 8

33. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Acids, Bases, and Salts in the Home Cleaning Products, continued Many household cleaners contain ammonia, a weak base. Solutions of ammonia can clean away light grease smears. Household bleach is a solution of a strong base, sodium hypochlorite (NaOCl). You are probably familiar with bleach’s ability to whiten fabrics. Bleach is also a strong disinfectant, a chemical substance that kills harmful bacteria or viruses. Chapter 8

34. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Bleach Section 3 Acids, Bases, and Salts in the Home Chapter 8

35. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Acids, Bases, and Salts in the Home Acids, Bases, and Salts in the Household An antacid is a weak base that neutralizes stomach acid. Sodium hydrogen carbonate and magnesium hydroxide (milk of magnesia) are examples. Shampoos are adjusted for an ideal pH. The pH of most shampoos is between 5 and 8. If shampoo is too basic, it can cause strands of hair to swell, giving them a dull, lifeless appearance. Chapter 8

36. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Antacid Section 3 Acids, Bases, and Salts in the Home Chapter 8

37. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Acids, Bases, and Salts in the Home Acids, Bases, and Salts in the Household, continued Acids keep fruit fresh longer. Acidic marinades made of vinegar or wine can be used to tenderize meats because they can denature proteins in the meat. Bacteria convert lactose, a sugar in milk, into lactic acid. The lactic acid denatures the protein casein in milk and changes the milk into yogurt. The strong base sodium hydroxide, also called lye, is used to unclog drains. Chapter 8

38. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Concept Mapping Section 3 Acids, Bases, and Salts in the Home Chapter 8

39. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Understanding Concepts 1. What is the pH of a solution with a hydroxide ion concentration of 1  10 –13 M? A.–13 B.1 C.7 D.13 Standardized Test Prep Chapter 8

40. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Understanding Concepts 1. What is the pH of a solution with a hydroxide ion concentration of 1  10 –13 M? A.–13 B.1 C.7 D.13 Standardized Test Prep Chapter 8

41. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Understanding Concepts 2. Which of the following is true of weak acids? F.They are less soluble in water than strong acids. G.They do not ionize as completely in water as strong acids. H.They have a pH value that is lower than that of strong acids. I.They do not react with bases to form a salt as do strong acids. Standardized Test Prep Chapter 8

42. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Understanding Concepts 2. Which of the following is true of weak acids? F.They are less soluble in water than strong acids. G.They do not ionize as completely in water as strong acids. H.They have a pH value that is lower than that of strong acids. I.They do not react with bases to form a salt as do strong acids. Standardized Test Prep Chapter 8

43. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Understanding Concepts 3. Which of the following pH ranges would include the equivalence point of the titration of a strong acid with a weak base? A.pH 2 to pH 6 B.pH 6 to pH 8 C.exactly pH 7 D.exactly pH 8 Standardized Test Prep Chapter 8

44. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Understanding Concepts 3. Which of the following pH ranges would include the equivalence point of the titration of a strong acid with a weak base? A.pH 2 to pH 6 B.pH 6 to pH 8 C.exactly pH 7 D.exactly pH 8 Standardized Test Prep Chapter 8

45. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Understanding Concepts 4. What property of detergents makes them more useful than soap for washing clothes and dishes in many parts of the country? Standardized Test Prep Chapter 8

46. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Understanding Concepts 4. What property of detergents makes them more useful than soap for washing clothes and dishes in many parts of the country? Answer: Detergents do not form insoluble salts with calcium as do soaps, so they work better in hard water. Standardized Test Prep Chapter 8

47. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Understanding Concepts 5. How can you determine by tasting which foods have a high concentration of one or more acidic compounds? Standardized Test Prep Chapter 8

48. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Understanding Concepts 5. How can you determine by tasting which foods have a high concentration of one or more acidic compounds? Answer: Acidic compounds have a sour taste. Standardized Test Prep Chapter 8

49. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Reading Skills Nitrogen and sulfur compounds formed by the combustion of fossil fuels react with oxygen and water in the air to form acids. These acids dissolve in water, forming acid precipitation, which can react with objects on which it falls. Limestone statues and decorations on buildings in areas with acidic rainfall have been severely damaged by the acid. On the other hand, granite statues and carvings tend to suffer much less damage under the same conditions. 6. Assess why one type of stone, limestone, is affected by acid precipitation much more than another type of stone, granite. Standardized Test Prep Chapter 8

50. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Reading Skills, continued 6. Assess why one type of stone, limestone, is affected by acid precipitation much more than another type of stone, granite. Answer: Limestone reacts more with acid than granite. Therefore, the compounds that make up limestone must be basic, and those in granite are not. Standardized Test Prep Chapter 8

51. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Interpreting Graphics Standardized Test Prep 7. What is occurring between the addition of 10 mL and 20 mL of NaOH? F.Hydrogen ion concentration is increasing. G.Hydroxide ion concentration is increasing. H.Hydronium ion concentration is increasing. I.Hydrogen ion and hydroxide ion concentrations are increasing. Chapter 8

52. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Interpreting Graphics 7. What is occurring between the addition of 10 mL and 20 mL of NaOH? F.Hydrogen ion concentration is increasing. G.Hydroxide ion concentration is increasing. H.Hydronium ion concentration is increasing. I.Hydrogen ion and hydroxide ion concentrations are increasing. Standardized Test Prep Chapter 8