Chemistry for Changing Times 12 th Edition Hill and Kolb Chapter 7 Acids and Bases: Please Pass the Protons John Singer Jackson Community College, Jackson, MI © 2010 Pearson Prentice Hall, Inc.

7/2 Acids and Bases: Experimental Definitions Acids: Taste sour. Turn litmus red. React with active metals to release hydrogen gas. React with bases to form water and a salt.

© 2010 Pearson Prentice Hall, Inc. 7/3 Acids and Bases: Experimental Definitions Bases: Taste bitter. Turn litmus blue. Feel slippery. React with acids to form water and a salt.

© 2010 Pearson Prentice Hall, Inc. 7/4 Acids and Bases: Experimental Definitions

© 2010 Pearson Prentice Hall, Inc. 7/5 Acids, Bases, and Salts Arrhenius Theory Acid: A molecular substance that ionizes in aqueous solution to form hydrogen ions (H + ).

© 2010 Pearson Prentice Hall, Inc. 7/6 Acids, Bases, and Salts Arrhenius Theory Base: A substance that produces hydroxide ions (OH-) in aqueous solution.

© 2010 Pearson Prentice Hall, Inc. 7/7 Acids, Bases, and Salts Neutralization: When an acid reacts with a base, the properties of each are neutralized and the products are water and a salt. Acid + Base → Water + Salt

© 2010 Pearson Prentice Hall, Inc. 7/8 Acids, Bases, and Salts Limitations of the Arrhenius Theory H + ions do not exist in water solution. Protons react with water to form hydronium ions (H 3 O + ). H + + H 2 O → H 3 O + The Arrhenius theory does not explain the basicity of ammonia and similar compounds. It only applies to reactions in aqueous solution.

© 2010 Pearson Prentice Hall, Inc. 7/9 Acids, Bases, and Salts Brønsted-Lowry Theory Acid: Proton donor HA + H 2 O → H 3 O + + A - Base: Proton acceptor NH 3 + H 2 O → NH OH -

© 2010 Pearson Prentice Hall, Inc. 7/10 Acids, Bases, and Salts Brønsted-Lowry Theory

© 2010 Pearson Prentice Hall, Inc. 7/11 Acidic and Basic Anhydrides Anhydride means without water. Nonmetal oxides are acidic anhydrides. SO 3 + H 2 O → H 2 SO 4

© 2010 Pearson Prentice Hall, Inc. 7/12 Acidic and Basic Anhydrides Metal oxides are basic anhydrides. Example: Lime (calcium oxide) reacts with water to form slaked lime (calcium hydroxide). CaO + H 2 O → Ca(OH) 2

© 2010 Pearson Prentice Hall, Inc. 7/13 Strong and Weak Acids and Bases Strong acids ionize completely in water solution. HCl(aq) → H + (aq) + Cl - (aq) Weak acids only partially ionize in water solution. HCN(aq) ↔ H + (aq) + CN - (aq)

© 2010 Pearson Prentice Hall, Inc. 7/14 Strong and Weak Acids and Bases Strong bases ionize completely in water solution. NaOH(aq) → Na + (aq) + OH - (aq) Weak bases only partially ionize in water solution. NH 3 (aq) + H 2 O ↔ NH 4 + (aq) + OH - (aq)

© 2010 Pearson Prentice Hall, Inc. 7/15 Strong and Weak Acids and Bases Ammonia accepts a proton from water, forming a basic solution.

© 2010 Pearson Prentice Hall, Inc. 7/16 Neutralization The reaction of an acid with a base is called neutralization. Water molecules are the result of the reaction between hydrogen ions and hydroxide ions. H + + OH - ↔ H 2 O

© 2010 Pearson Prentice Hall, Inc. 7/17 Neutralization During neutralization, an acid reacts with a base, forming water and a salt.

© 2010 Pearson Prentice Hall, Inc. 7/18 Neutralization The amount of acid (or base) in a solution is determined by careful neutralization.

© 2010 Pearson Prentice Hall, Inc. 7/19 The pH Scale pH is a means of expressing the acidity or basicity of a solution.

© 2010 Pearson Prentice Hall, Inc. 7/20 The pH Scale pH means “power” of hydrogen. pH = -log[H + ]

© 2010 Pearson Prentice Hall, Inc. 7/21 The pH Scale

© 2010 Pearson Prentice Hall, Inc. 7/22 Buffers and Conjugate Acid- Base Pairs Conjugate acid-base pairs are compounds or ions that differ by one proton (H + ). For example, the chloride ion (Cl - ) is the conjugate base of the acid, hydrochloric acid (HCl).

© 2010 Pearson Prentice Hall, Inc. 7/23 Buffers and Conjugate Acid- Base Pairs Buffer solutions contain a weak acid and its conjugate base. Such solutions are capable of maintaining a nearly constant pH when small amounts of acid or base are added.

© 2010 Pearson Prentice Hall, Inc. 7/24 Acid Rain Nonmetal oxides present in air react with water, forming acidic solutions. Rain with a pH of less than 5.6 is considered to be acid rain. Carbon dioxide (CO 2 ), sulfur dioxide (SO 2 ), nitrogen monoxide (NO), and nitrogen dioxide (NO 2 ) are the major nonmetallic oxides responsible for acid rain formation.

© 2010 Pearson Prentice Hall, Inc. 7/25 Antacids: A Basic Remedy Hyperacidity is when the stomach secretes too much acid. Antacids are often taken to neutralize excess acid and reduce the symptoms of hyperacidity. Excessive use of antacids can lead to an increase in the pH of blood, a condition known as alkalosis.

© 2010 Pearson Prentice Hall, Inc. 7/26 Antacids: A Basic Remedy

© 2010 Pearson Prentice Hall, Inc. 7/27 Antacids: A Basic Remedy SubstanceFormulaProduct(s) Sodium bicarbonate NaHCO 3 Baking soda Calcium carbonate CaCO 3 Tums® Aluminum hydroxide Al(OH) 3 Amphojel® Magnesium hydroxide Mg(OH) 2 Milk of Magnesia®

© 2010 Pearson Prentice Hall, Inc. 7/28 Acids and Bases in Industry and at Home Sulfuric acid is the leading chemical substance produced in the U.S. It is used to manufacture fertilizers and industrial chemicals. It is the acid of automotive batteries. Production is 40 billion kg/year.

© 2010 Pearson Prentice Hall, Inc. 7/29 Acids and Bases in Industry and at Home Hydrochloric acid has a number of uses. It is used as a rust remover, and it removes lime from mortar and household plumbing fixtures. It can be purchased from hardware stores as muriatic acid. Annual U.S. production is 4 billion kg.

© 2010 Pearson Prentice Hall, Inc. 7/30 Acids and Bases in Industry and at Home Lime (CaO) is produced by heating limestone (CaCO 3 ). CaCO 3 + heat → CaO + CO 2 Lime can be slaked by reacting with water to make calcium hydroxide (Ca(OH) 2 ). Slaked lime is used to make mortar and cement and to sweeten soil. Annual U.S. production is 22 billion kg.

© 2010 Pearson Prentice Hall, Inc. 7/31 Acids and Bases in Industry and at Home Soil can be “sweetened” by adding slaked lime [Ca(OH) 2 ].

© 2010 Pearson Prentice Hall, Inc. 7/32 Acids and Bases in Industry and at Home Sodium hydroxide, also known as lye, can be purchased for home use as oven cleaner or drain cleaners. It is used commercially to make soap. Annual U.S. production is 9 billion kg.

© 2010 Pearson Prentice Hall, Inc. 7/33 Acids and Bases in Industry and at Home Ammonia is produced for use as fertilizer and in household cleaning products. Production is about 11 billion kg/year.

© 2010 Pearson Prentice Hall, Inc. 7/34 Acids and Bases in Health and Disease Concentrated acids and bases are corrosive to tissue and are health hazards. They can denature proteins in living cells. The human body has wonderful mechanisms for maintaining the proper pH of tissue, blood, and body fluids.