Calculator
Enter half-reactions already balanced for atoms first. This calculator matches electrons and shows the required scaling factors.
Example Data Table
These examples show the electron-matching stage after atoms have already been balanced in each half-reaction.
| Case | Oxidation Half | Reduction Half | Electron Counts | LCM | Suggested Multipliers | Medium |
|---|---|---|---|---|---|---|
| Iron with permanganate | Fe2+ -> Fe3+ + e- | MnO4- + 8H+ + 5e- -> Mn2+ + 4H2O | 1 and 5 | 5 | 5 and 1 | Acidic |
| Iodide with dichromate | 2I- -> I2 + 2e- | Cr2O7^2- + 14H+ + 6e- -> 2Cr3+ + 7H2O | 2 and 6 | 6 | 3 and 1 | Acidic |
| Sulfite with permanganate | SO3^2- + H2O -> SO4^2- + 2H+ + 2e- | MnO4- + 8H+ + 5e- -> Mn2+ + 4H2O | 2 and 5 | 10 | 5 and 2 | Acidic |
| Hydrogen peroxide with iodide | 2I- -> I2 + 2e- | H2O2 + 2H+ + 2e- -> 2H2O | 2 and 2 | 2 | 1 and 1 | Acidic |
Formula Used
1. Effective oxidation electrons
Effective oxidation electrons = direct electrons
or
Effective oxidation electrons = oxidation-number change per atom × atoms changed
2. Effective reduction electrons
Effective reduction electrons = direct electrons
or
Effective reduction electrons = reduction-number change per atom × atoms changed
3. Electron matching
Balanced electron count = LCM(oxidation electrons, reduction electrons)
Oxidation multiplier = LCM ÷ oxidation electrons
Reduction multiplier = LCM ÷ reduction electrons
4. Medium corrections
Acidic solutions use H2O and H+.
Basic solutions use H2O and OH- after acidic balancing.
Neutral solutions usually simplify with careful H2O and OH- handling.
There is no single short algebraic formula for every redox equation. This tool applies the standard electron-balance framework used in the half-reaction method.
How to Use This Calculator
- Write oxidation and reduction half-reactions separately.
- Balance all elements except hydrogen and oxygen first.
- Choose the reaction medium: acidic, basic, or neutral.
- Enter each half-reaction into the correct text box.
- Type direct electron counts if they are already known.
- Or enter oxidation-number change and atoms changed.
- Submit the form to calculate the least common multiple.
- Use the shown multipliers to scale both half-reactions.
- Add the scaled halves and cancel equal electrons.
- Then simplify repeated water, H+, or OH- terms.
FAQs
1. What does this calculator actually balance?
It balances the electron-matching stage of redox work. You enter the oxidation and reduction half-reactions, then the tool finds the least common electron multiple and the required scaling factors.
2. Can it solve every full redox equation automatically?
It is designed for the half-reaction workflow, not full chemical parsing. It speeds up the most error-prone step and gives a clean structure for combining the final balanced equation.
3. When should I use oxidation-number change fields?
Use them when you know how many oxidation numbers changed per atom and how many atoms changed. The calculator multiplies those values to get effective electrons automatically.
4. Why is the least common multiple important?
Oxidation and reduction must exchange equal electrons. The least common multiple gives the smallest shared electron count, which produces the lowest whole-number scaling for both half-reactions.
5. How do acidic and basic media change the process?
Acidic solutions use H+ and H2O during balancing. Basic solutions are often balanced as acidic first, then converted by adding OH- to both sides and simplifying water.
6. What should I type in the half-reaction boxes?
Type the half-reaction text clearly, such as Fe2+ -> Fe3+ + e-. Include water, H+, or OH- if you already balanced them before the electron-matching stage.
7. What can I export from this page?
You can export the calculated summary as a CSV file or a PDF file. Both exports include the reaction label, electron counts, multipliers, scaled halves, and guidance.
8. How can I verify my final balanced equation?
After combining the scaled half-reactions, check that atoms match on both sides and total charge is identical. A correct redox balance always conserves both mass and charge.