1. Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Chapter 5 Chemical Quantities and Reactions 5.5 Oxidation−Reduction Reactions 1

2. Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Oxidation−Reduction Reactions An oxidation–reduction reaction provides us with energy from food provides electrical energy in batteries occurs when iron rusts: 4Fe(s) + 3O 2 (g) 2Fe 2 O 3 (s) 2

3. Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Oxidation−Reduction In an oxidation–reduction reaction, electrons are transferred from one substance to another. 3

4. Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Oxidation−Reduction ReducedOxidized 4

5. Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Oxidation and Reduction 2Cu(s) + O 2 (g) 2CuO OIL RIG Oxidation is loss of electrons. 2Cu(s) 2Cu 2+ (s) + 4e − Reduction is gain of electrons. O 2 (g) + 4e − 2O 2− (s) 5 The green patina on copper is due to oxidation

6. Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Zn replaces Cu 2+ 6

7. Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Zn Transfers Electrons to Cu 2+ OILOxidation is losing electrons. RIGReduction is gaining electrons. 7

8. Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check Identify each of the following as oxidation or reduction: __A. Sn(s) Sn 4+ (aq) + 4e − __B. Fe 3+ (aq) + 1e − Fe 2+ (aq) __C. Cl 2 (g) + 2e − 2Cl −  (aq) 8

9. Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution Identify each of the following as oxidation or reduction: Oxidation__A. Sn(s) Sn 4+ (aq) + 4e − Reduction__B. Fe 3+ (aq) + 1e − Fe 2+ (aq) Reduction__C. Cl 2 (g) + 2e − 2Cl − (aq) 9

10. Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check In light-sensitive sunglasses, UV light initiates an oxidation–reduction reaction. UV light 2Ag + + 2Cl − 2Ag + Cl 2 A. Which reactant is oxidized? B. Which reactant is reduced? 10

11. Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution In light-sensitive sunglasses, UV light initiates an oxidation-reduction reaction. uv light 2Ag + + 2Cl − 2Ag + Cl 2 A. Which reactant is oxidized? 2Cl − Cl 2 + 2e − B. Which reactant is reduced? 2Ag + + 2e − 2Ag 11

12. Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Oxidation – Reduction in Biological Systems The oxidation of a typical biochemical molecule can involve the transfer of two hydrogen atoms (or 2H + and 2e − ) to a proton acceptor such as the coenzyme FAD (flavin adenine dinucleotide). 12

13. Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Characteristics of Oxidation and Reduction 13

14. Chemistry An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Characteristics of Oxidation and Reduction Methyl alcohol formaldehyde Oxidation (loss of H as hydrogen gas) CH 3 OH H 2 CO + 2H 2 Formaldehyde formic acid 2H 2 CO + O 2 2H 2 CO 2 Oxidation (addition of O) 14