General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake 6.3 Oxidation–Reduction Reactions Chapter 6 Chemical Reactions and Quantities © 2013 Pearson Education, Inc. Lectures

© 2013 Pearson Education, Inc. Chapter 6, Section 3 2 Everyday Oxidation–Reduction Reactions In an oxidation–reduction reaction,  electrons are transferred from one substance to another.  if one substance loses electrons, another substance must gain electrons.  energy is provided to us from food.  electrical energy is provided in batteries.  iron rusts.

© 2013 Pearson Education, Inc. Chapter 6, Section 3 3 In oxidation–reduction reactions,  the process of losing electrons is called oxidation. Oxidation Is a Loss of electrons. (OIL)  the process of gaining electrons is called reduction. Reduction Is a Gain of electrons. (RIG) Transfer of Electrons

© 2013 Pearson Education, Inc. Chapter 6, Section 3 4 Oxidation and Reduction

© 2013 Pearson Education, Inc. Chapter 6, Section 3 5 Oxidized or Reduced?

© 2013 Pearson Education, Inc. Chapter 6, Section 3 6 Oxidation and Reduction, Formation of CaS In the reaction:  the reactant, Ca has a charge of 0 and the product, CaS contains a Ca 2+ ion.  calcium loses two electrons, meaning oxidation has taken place.  the reactant, S has a charge of 0 and the product, CaS contains an S 2− ion.  sulfur gains two electrons, meaning reduction has taken place.

© 2013 Pearson Education, Inc. Chapter 6, Section 3 7 Oxidation and Reduction, Formation of CaS Adding the two reactions, oxidation and reduction, gives us the overall reaction. The overall reaction is written as:

© 2013 Pearson Education, Inc. Chapter 6, Section 3 8 Zn and Cu 2+ When zinc is added to copper(II) sulfate, zinc undergoes oxidation, while copper undergoes reduction.

© 2013 Pearson Education, Inc. Chapter 6, Section 3 9 Electron Transfer from Zn to Cu 2+ Oxidation: electron loss Reduction: electron gain

© 2013 Pearson Education, Inc. Chapter 6, Section 3 10 Identify each of the following reactions as oxidation or reduction. Learning Check

© 2013 Pearson Education, Inc. Chapter 6, Section 3 11 Identify each of the following reactions as oxidation or reduction. Solution

© 2013 Pearson Education, Inc. Chapter 6, Section 3 12 Learning Check In light-sensitive sunglasses, UV light initiates an oxidation-reduction reaction. 1. Which reactant is oxidized? 2. Which reactant is reduced?

© 2013 Pearson Education, Inc. Chapter 6, Section 3 13 In light-sensitive sunglasses, UV light initiates an oxidation-reduction reaction. 1. Which reactant is oxidized? Cl − 2. Which reactant is reduced? Ag + Solution

© 2013 Pearson Education, Inc. Chapter 6, Section 3 14 Learning Check Identify the substances that are oxidized and reduced in each of the following reactions.

© 2013 Pearson Education, Inc. Chapter 6, Section 3 15 Solution Identify the substances that are oxidized and reduced in each of the following reactions. 1. Mg is oxidized.Mg(s) Mg 2+ (aq) + 2e − H + is reduced.2H + (aq) + 2e − H 2 (g) 2. Al is oxidized. 2Al(s) 2Al 3+ (s) + 6e − Br is reduced.3Br 2 (l) + 6e − 6Br − (s)

© 2013 Pearson Education, Inc. Chapter 6, Section 3 16 Oxidation–Reduction in Biological Systems In biological systems, oxidation may involve  the loss of H or  the gain of O. In biological systems, reduction may involve  the gain of H or  the loss of O.

© 2013 Pearson Education, Inc. Chapter 6, Section 3 17 Oxidation–Reduction in Biological Systems

© 2013 Pearson Education, Inc. Chapter 6, Section 3 18 Characteristics of Oxidation and Reduction