1. Unit 9 Acid-Base Chemistry Chapters 14 & 15

2. ACIDS & BASES Chapter 14

3. Properties of Acids Taste sour. React with metals to release H 2 gas. React with bases to produce salts and water. Change the color of acid-base indicators. Conduct electric current. Chapter 14 – Section 1: Properties of Acids and Bases

4. Properties of Bases Taste bitter. Feel slippery. React with acids to produce salts and water. Change the color of acid-base indicators. Conduct electric current. Chapter 14 – Section 1: Properties of Acids and Bases

5. Arrhenius Acids and Bases An Arrhenius acid produces hydrogen ions, H +, in aqueous solution. An Arrhenius base produces hydroxide ions, OH −, in aqueous solution. A strong acid (or base) ionizes completely. A weak acid (or base) releases only a few ions. Chapter 14 – Section 1: Properties of Acids and Bases

6. Brønsted-Lowry Acids and Bases A Brønsted-Lowry acid is a molecule or ion that is a proton donor. A Brønsted-Lowry base is a molecule or ion that is a proton acceptor. Example: –Hydrogen chloride acts as a Brønsted-Lowry acid when it reacts with ammonia. –Ammonia accepts a proton from the hydrochloric acid. It acts as a Brønsted-Lowry base. Chapter 14 – Section 2: Acid-Base Theories

7. Lewis Acids and Bases A Lewis acid is an atom, ion, or molecule that accepts an electron pair to form a covalent bond. A Lewis base is an atom, ion, or molecule that donates an electron pair to form a covalent bond. The Lewis definition is the broadest of the three definitions. Chapter 14 – Section 2: Acid-Base Theories

8. Comparing the Three Definitions Comparison Chart (from Page 482) Visual Concept Chapter 14 – Section 2: Acid-Base Theories

9. Amphoteric Compounds An amphoteric substance is one that can react as either an acid or a base. Example: water water can act as an acid. Water can act as a base. Chapter 14 – Section 3: Acid-Base Reactions base acid acid base Visual Concept

10. pH Chapter 15

11. The pH Scale pH is defined as the negative of the common logarithm of the hydronium ion concentration. pH = − log [H 3 O + ] Example: a neutral solution has a [H 3 O + ] = 1×10 − 7 The logarithm of 1×10 − 7 is − 7.0. pH = − log [H 3 O + ] = − log(1 × 10 − 7 ) = − ( − 7.0) = 7.0 Chapter 15 – Section 1: Aqueous Solutions and the Concept of pH

12. The pH Scale (continued) Chapter 15 – Section 1: Aqueous Solutions and the Concept of pH

13. The pH Scale Sample Problem Identify each of the following solutions as acidic, basic, or neutral: a.) [H 3 O + ] = 1.0 x 10 -7 b.) pH = 13.0 c.) [H 3 O + ] = 1.0 x 10 -5 d.) pH = 1.0 Chapter 15 – Section 1: Aqueous Solutions and the Concept of pH pH = 7 neutral basic pH = 5 acidic

14. The pOH Scale pOH is defined as the negative of the common logarithm of the hydroxide ion concentration. pH = − log [OH - ] Example: a basic solution has a [OH - ] = 1×10 − 3 The logarithm of 1×10 − 3 is − 3.0. pOH = − log [OH - ] = − log(1 × 10 − 3 ) = − ( − 3.0) = 3.0 Chapter 15 – Section 1: Aqueous Solutions and the Concept of pH

15. Comparing pH and pOH The sum of the pH and pOH of a solution is 14. pH + pOH = 14.0 Chapter 15 – Section 1: Aqueous Solutions and the Concept of pH

16. pH and pOH Sample Problem An aqueous solution has a pH of 4.0. Determine: a.) The hydronium ion concentration. b.) The hydroxide ion concentration. Chapter 15 – Section 1: Aqueous Solutions and the Concept of pH [H 3 O + ] =1.0 x 10 -4 pOH = 14.0 - pH= 14.0 – 4.0 pOH = 10.0 [OH - ] =1.0 x 10 -10