Definitions , Theories, & Properties o f Acids & Bases

1. Definitions, Theories, & Properties of Acids & Bases Chapter 16

2. Properties • Both acids and bases ionize or dissociate in water • Acids: taste sour, conduct electricity, cause certain indicators to change color,turn blue litmus paper red, and react with metals to form H2 gas • Bases: taste bitter, feel slippery, conduct electricity, and cause certain indicators to change color, turn red litmus paper blue

3. Knowledge Level Question #1 iRespond Question Multiple Choice F An unknown solution conducts electricity. Upon further testing, scientists find that hydrogen gas is emitted when it is dropped onto magnesium ribbon. Classify the substance according to its properties. C.) A.) Acid D.) B.) Base E.)

4. First Acid Definition • Arrhenius definition for acid: compound that produces hydrogen ions (H+) when dissolved in water. • Ex. HCl(g) is named hydrogen chloride. BUTHCl(aq) is named hydrochloric acid. • Let’s write the dissociation reaction for the HCl example. HCl + H2O  H+ + Cl-

5. First Base Definition • Arrhenius definition of base: a compound that produces hydroxide ions (OH-) when dissolved in water. • Ex. NaOH(s) is named sodium hydroxide and is NOT a base. BUTNaOH (aq) is named sodium hydroxide and IS a base. • Let’s write the dissociation reaction for the NaOH example. NaOH + H2O  Na+ + OH-

6. iRespond Question Multiple Choice F Knowledge Level Question #2 Which of the following aqueous solutions is an Arrhenius acid? A.) BaH2 B.) Ba(OH)2 C.) HBr D.) Both a and c E.)

7. Arrhenius Acids & Bases • Acids are hydrogen-containing compounds that ionize to yield hydrogen ions in aqueous solution... • Bases are compounds that ionize to yield hydroxide ions in aqueous solution... • BUT, NH3is a base! Arrhenius’ theory doesn’t hold up in every case, so...

8. Bronsted-Lowry Acids and Bases • An acid is a hydrogen-ion donor, and a base is a hydrogen-ion acceptor. • Example: NH3(aq) + H2O(l)  NH4+(aq) + OH-(aq) • Analyze the compounds as they react. What happens during the reaction? • NH3 accepts an H+ to become NH4+ • H2O donates an H+ to become OH- BASE ACID

9. Acid-Base Pairs • According to this theory, an acid has a conjugate base. Likewise, a base has a conjugate acid. • We refer to them as conjugate acid-base pairs. The two differ only by a hydrogen. • Example: NH3 and NH4+, H2O and OH-

10. Application of the Bronsted-Lowry Theory • H2SO4 + H2O  H3O+ + HSO4- • Label the acid, base, conjugate acid, and conjugate base. • Write conjugate acid-base pairs.

11. iRespond Question Multiple Choice F Application Level Question #3 Which of the following substances is the acid in the H2SO4 dissociation example? A.) H2SO4 B.) H2O C.) H3O+ D.) HSO4- E.)

12. Individual Practice of Application of Bronsted-Lowry Theory • Find the “Bronsted-Lowry Acids and Bases Practice Problems” worksheet in your practice packet. • Answer Part I.

13. Individual Practice of Application of Bronsted-Lowry Theory • Identifying acid-base pairs in dissociation reactions can be a bit confusing at first. • Remember, the acid and base will be found in the reactants. The conjugate acid and base will be found in the products. • The acid will donate an H+ to become the conjugate base. The two substances will differ by ONLY one H+. Therefore, the acid will have one additional H+. • The base will accept an H+ to become the conjugate acid. The two will differ by ONLY one H+. Therefore, the conjugate acid will have one additional H+. • Complete Parts II and III of the “Bronsted-Lowry Acids and Bases Practice Problems” now.