19.2 How to Balance Oxidation Reduction Reactions
Oxidizing Agent (Oxidant) – species that is reduced
Reducing Agent (Reductant) – species that is oxidized
HOW TO BALANCE REDOX REACTIONS (HALF-REACTION METHOD)
1. Split into half reactions.
2. Balance all elements except oxygen and hydrogen.
3. Balance oxygen by adding H2O.
4. Balance hydrogen by adding H+.
5. Balance the charge by adding electrons.
6. Multiply half reactions by factors to make the number of electrons the same.
7. Combine half reactions canceling anything that shows up on both sides of the reaction.
8. Conditional: If balancing in base add the same number of OH- to both sides as H+ present.
On the side with the H+ the H+/OH- combine to form H2O.
9. Cancel any excess H2O that now shows up on both sides of the reaction (if necessary).
Balance the following redox reactions:
H2O2(aq) + PbS(s) → PbSO4(s) + H2O(l)
MnO4-(aq) + I-(aq) → Mn2+(aq) + I2(s)