Balancing Redox Reactions
Balance atoms and charges using half-reactions.
About this topic
Redox equations must balance both atoms and charge. In the half-reaction method: split the equation into oxidation and reduction half-reactions; balance atoms other than O and H; balance O by adding H2O; balance H by adding H+ (in acid); balance charge with electrons; multiply half-reactions so electrons match; add them and cancel. In basic solution, add OH− to neutralise H+.
Each half-reaction shows one process, for example Fe2+ gives Fe3+ + e- for oxidation. The electrons lost in one half must equal the electrons gained in the other, so you multiply by whole numbers. The final equation has no electrons. Check that atoms and charges are equal on both sides. Using oxidation numbers is an alternative method for simpler equations.
Worked example: MnO4- + Fe2+ in acid. Reduction: MnO4- + 8H+ + 5e- gives Mn2+ + 4H2O. Oxidation: Fe2+ gives Fe3+ + e-, times 5. Adding gives MnO4- + 8H+ + 5Fe2+ gives Mn2+ + 5Fe3+ + 4H2O. This reaction is used in titrations because the purple permanganate fades to colourless.
Typical errors include forgetting to balance charge, adding electrons on the wrong side, not multiplying both halves and using H+ in basic solution. Always check the final charge.
Key ideas
- Split into two halves
- Balance electrons
- Add them back
Quick check
Use cases: where Balancing Redox Reactions helps
- Homework: review the key idea behind Balancing Redox Reactions before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Balancing Redox Reactions without notes.
- Visual learning: play with the interactive lab to see how Balancing Redox Reactions changes when you adjust its inputs.
- Teaching a friend: explain Balancing Redox Reactions in your own words, then compare your version with the key ideas.
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Frequently asked questions
What is Balancing Redox Reactions?
Balance atoms and charges using half-reactions.
What will I learn in Balancing Redox Reactions?
Split into two halves. Balance electrons. Add them back.
Is Balancing Redox Reactions part of Chemistry?
Yes. It is one of 150 Chemistry topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Balancing Redox Reactions lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Balancing Redox Reactions?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
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