Redox Equations

1. Redox Equations 9.2.1, 9.2.2, 9.2.3, 9.2.4 Text pg. 846-850

2. Balancing Redox Reactions • Many Redox rxns are complex and difficult to balance . • A systematic approach to balancing these reaction is required.

3. MnO41- (aq) + C2O42- (aq)  Mn2+(aq) + CO2(aq) MnO41- = oxidizing agent (it is doing the oxidizing to the other substance, but itself is being reduced). C2O42- = reducing agent (it is doing the reducing to the other substance, but itself is being oxidized). Balancing Redox Equations 1 • Divide the equation into 2 half reactions—one for oxidation, one for reduction. • Balance each half reaction • Balance elements other than H and O • Balance O by adding H2O as needed • Balance H by adding H+ as needed.(acidic solution) • Balance charge by adding e- as needed. • Multiply half reactions by integers so that the # of e- lost in one reaction = # of e- gained in the other reaction. • Add the two half reactions. Simplify by canceling species that appear on both sides of the arrow. • Check your work. Make sure that both the atoms and charges balance

4. Cr2O72- (aq) + Cl1- (aq)  Cr 3+ (aq) + Cl2 (g) Cr2O72- = oxidizing agent (it is doing the oxidizing to the other substance, but itself is being reduced). Cl- = reducing agent (it is doing the reducing to the other substance, but itself is being oxidized). Balancing Redox Equations 2 • Divide the equation into 2 half reactions—one for oxidation, one for reduction. • Balance each half reaction • Balance elements other than H and O • Balance O by adding H2O as needed • Balance H by adding H+ as needed. .(acidic solution) • Balance charge by adding e- as needed. • Multiply half reactions by integers so that the # of e- lost in one reaction = # of e- gained in the other reaction. • Add the two half reactions. Simplify by canceling species that appear on both sides of the arrow. • Check your work. Make sure that both the atoms and charges balance

5. Quick Thoughts • Next week = lab (Safety Contracts!) • Semester 2 final

7. Balancing Redox Equations 3 • Divide the equation into 2 half reactions—one for oxidation, one for reduction. • Balance each half reaction • Balance elements other than H and O • Balance O by adding H2O as needed • Balance H by adding H+ as needed. .(acidic solution) • Balance charge by adding e- as needed. • Multiply half reactions by integers so that the # of e- lost in one reaction = # of e- gained in the other reaction. • Add the two half reactions. Simplify by canceling species that appear on both sides of the arrow. • Check your work. Make sure that both the atoms and charges balance Cu (s) + NO31- (aq)  Cu 2+(aq) + NO2(aq)

8. Balancing Redox Equations 4 • Divide the equation into 2 half reactions—one for oxidation, one for reduction. • Balance each half reaction • Balance elements other than H and O • Balance O by adding H2O as needed • Balance H by adding H+ as needed. .(acidic solution) • Balance charge by adding e- as needed. • Multiply half reactions by integers so that the # of e- lost in one reaction = # of e- gained in the other reaction. • Add the two half reactions. Simplify by canceling species that appear on both sides of the arrow. • Check your work. Make sure that both the atoms and charges balance Mn 2+ (aq) + NaBiO3 (s)  Bi 3+(aq) + MnO4 1- (aq) + Na1+(aq)

9. Text p. 884 • Text p. 884 • Problems # 20a, b, c, d 22 a, b, c, d “acidic solution only”