Untitled - Kelly Walsh High School

Electrochemistry 267
Quick Tip
Some redox reactions may be simply balanced by inspection. However, many
are complex and require the use of a systematic method. There are two methods
commonly used to balance redox reactions: the oxidation number method
and the ion-electron method.
Your text or instructor may give you what appears to be a variation of these steps.
The words may differ, but the ideas behind each step are the same.
To balance a redox reaction using the oxidation number method, follow the following
rules:
1. Assign oxidation numbers to all elements in the reaction.
2. Identify what undergoes oxidation and what undergoes reduction by the
change in oxidation numbers.
3. Calculate the number of electrons lost in oxidation and electrons gained in
reduction.
4. Multiply one or both of these numbers by factors to make electron loss
equal to electron gain and then use them as balancing coefficients.
5. Complete the balancing by inspection.
To balance a redox reaction using the ion-electron method, follow the following
rules: (Several variations of this method are used.)
1. Assign oxidation numbers and begin the half-reactions, one for oxidation,
and one for reduction.
2. Balance all atoms except O and H.
3. Balance oxygen atoms.
4. Balance hydrogen atoms.
5. Balance charges by adding electrons.
6. Adjust the half-reactions to give equal numbers of electrons.
7. Add and cancel (the electrons must cancel)
8. Check