1. Balancing Redox Reaction Equations
Chapter 9.2

2. Two Methods for Balancing
The Half-Reactions Method
The Oxidation Numbers Method
Both methods are based on the idea that electrons are neither created nor destroyed during a redox reaction. They are simply transferred from the species being oxidized to the species being reduced
You must be able to balance redox reaction equations using both methods
You must be able to balance redox reaction equations in both acidic solution and basic solution

3. The Half-Reactions Method
Identify and write down the unbalanced half-reactions (do this by first assigning oxidation numbers)
Balance atoms and charges in each half-reaction (use H2O to balance O, H+ to balance H, and e- to balance charge)
Multiply each half-reaction by an integer such that the number of electrons cancel
Add the half-reactions and cancel
For reactions that occur in basic solution follow this additional step: Add OH- to both sides for every H+ present, combining to yield H2O on the H+ side then cancel if necessary

4. The Half-Reactions Method

5. The Oxidation Numbers Method
Assign oxidation numbers and determine the atom that is oxidized and the atom that is reduced
Determine the number of electrons lost or gained per atom
Determine the number of electrons lost or gained per reactant molecule
Multiply by an integer such that the number of electrons cancel
Use these integers as coefficients for the reactants
Balance atoms (use H2O to balance O, and H+ to balance H)
For reactions that occur in basic solution follow this additional step: Add OH- to both sides for every H+ present, combining to yield H2O on the H+ side then cancel if necessary

6. The Oxidation Numbers Method