2. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 1 Acids, Bases, and pH  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. Objectives Chapter 8

3. Copyright © by Holt, Rinehart and Winston. All rights reserved.  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. What Are Acids? Section 1 Acids, Bases, and pH Chapter 8

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

5. Copyright © by Holt, Rinehart and Winston. All rights reserved.  An electrolyte is a substance that dissolves in water to give a solution that conducts an electric current. What Are Acids? continued 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.

6. Copyright © by Holt, Rinehart and Winston. All rights reserved.  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 What Are Acids? continued Section 1 Acids, Bases, and pH Chapter 8

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

8. Copyright © by Holt, Rinehart and Winston. All rights reserved.  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. What Are Bases? Section 1 Acids, Bases, and pH Chapter 8

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

10. Copyright © by Holt, Rinehart and Winston. All rights reserved.  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. What is pH? Section 1 Acids, Bases, and pH Chapter 8

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

13. Copyright © by Holt, Rinehart and Winston. All rights reserved.  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. What is pH? continued Section 1 Acids, Bases, and pH Chapter 8

14. Copyright © by Holt, Rinehart and Winston. All rights reserved.  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. What is pH? continued Section 1 Acids, Bases, and pH Chapter 8

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

16. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 Reactions of Acids with Bases  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 Acid-Base Reactions Chapter 8

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

18. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 Reactions of Acids with Bases  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 Acid-Base Reactions, continued Chapter 8

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

20. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 Reactions of Acids with Bases  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. Acid-Base Reactions, continued Chapter 8

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

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

23. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 Reactions of Acids with Bases  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 Salts Chapter 8

24. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 3 Acids, Bases, and Salts in the Home  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. Objectives Chapter 8

25. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 3 Acids, Bases, and Salts in the Home  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. Cleaning Products Chapter 8

26. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 3 Acids, Bases, and Salts in the Home  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. Cleaning Products, continued Chapter 8

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

28. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 3 Acids, Bases, and Salts in the Home  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. Acids, Bases, and Salts in the Household Chapter 8

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

30. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 3 Acids, Bases, and Salts in the Home  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. Acids, Bases, and Salts in the Household, continued Chapter 8