1. Balancing Redox Reactions

2. Balancing Reactions in Acidic Solutions
Assign oxidation numbers
Split into two half reactions
Balance all atoms except H and O
Balance O’s by adding H2O(l)
Balance H’s by adding H+(aq)
Balance the charges by adding electrons
Check: the number of electrons should be equal to the change in oxidation number
Combine the half reactions
Multiply the half reactions by a coefficient so that the electrons cancel out
Cancel out any species that appear on both sides, e.g. H2O(l) and H+(aq)

3. Balancing Reactions in Basic Solutions
Assign oxidation numbers
Balance the two half reactions the same as in acidic conditions
Combine the half reactions
Multiply the half reactions by a coefficient so that the electrons cancel out
Cancel out any species that appear on both sides
For every H+(aq) add OH-(aq) to both sides
H+(aq) and OH-(aq) on the same side become H2O(l)
Cancel out H2O(l) molecules that appear on both sides

4. Practice
Balancing Worksheet
P. 668 #2-4
P. 673 #6-8
P. 673 #2-4