1. Outline:4/2/07 Today: Continue Chapter 19  Balancing redox reactions è Dr. Peaslee away today – back Wed. è 5 CAPA sets remain! è 4 weeks of classes remain! è 3 chem seminars remain!

2. Example Separate the following unbalanced redox processes into half-reactions. All occur in aqueous solution: a. Cr 2 O 7 2- (aq) + Fe 2+ (aq)  Cr 2+ (aq) + Fe 3+ (aq) b. H 2 O 2(aq) + SO 3- + (aq)  SO 4 2- (aq) c. BrO 2 - (aq)  BrO 3 - (aq) + Br - (aq)

3. Balancing REDOX Reactions Example 1: Acidic conditions MnO 4  + Br   Mn 2+ + Br 2 Example 2: Basic conditions MnO 4  + SO 3   MnO 4 2  + SO 4 2 

4. Now, combine half-reactions Example 1: Acidic conditions MnO 4   Mn 2+ 5 e  + 8 H + + MnO 4   Mn 2+ + 4 H 2 O Br   Br 2 2 Br   Br 2 2 Br   Br 2 + 2 e   2  5 16 H + + 2 MnO 4  + 10 Br   2 Mn 2+ + 8 H 2 O + 5 Br 2 MnO 4   Mn 2+ + 4 H 2 O 8 H + +

5. Example 2: Basic conditions Now, combine half-reactions MnO 4   MnO 4 2  SO 3 2-  SO 4 2-  2 2 OH  + 2 MnO 4  + SO 3   2 MnO 4 2  + SO 4 2  + H 2 O e  + H 2 O + SO 3 2-  SO 4 2- H 2 O + SO 3 2-  SO 4 2- + 2 H + 2 OH - + H 2 O + SO 3 2-  SO 4 2- + 2 H 2 O2 OH  + H 2 O + SO 3 2   SO 4 2  + 2 H 2 O +2e 

6. Worksheet #11