Redox Equation Balancer
Balance oxidation-reduction equations in acidic or basic solution and see the half-reaction steps.
Try an example:
Balanced Equation
MnO₄⁻ + 5Fe²⁺ + 8H⁺ → Mn²⁺ + 5Fe³⁺ + 4H₂O
Acidic solution
- Atoms balanced
- Charge balanced
- Electrons transferred: 5 e⁻
Half-reaction methodHow it was balanced
Step 1 — Split the reaction
Oxidation
Fe²⁺ → Fe³⁺
Reduction
MnO₄⁻ → Mn²⁺
Step 2 — Balance each half-reaction
Fe²⁺ → Fe³⁺ + e⁻
MnO₄⁻ + 8H⁺ + 5e⁻ → Mn²⁺ + 4H₂O
Step 3 — Match the electrons
Multiply by 5:
5Fe²⁺ → 5Fe³⁺ + 5e⁻
Reduction half-reaction:
MnO₄⁻ + 8H⁺ + 5e⁻ → Mn²⁺ + 4H₂O
Step 4 — Add the half-reactions
Electrons cancel, giving the final equation.
Check the balance
| Element | Reactants | Products |
|---|---|---|
| Fe | 5 | 5 |
| H | 8 | 8 |
| Mn | 1 | 1 |
| O | 4 | 4 |
Total charge: +17 = +17
Reactants: MnO₄⁻ = -1 · 5Fe²⁺ = +10 · 8H⁺ = +8
Products: Mn²⁺ = +2 · 5Fe³⁺ = +15
Fully balanced
Oxidation
Fe²⁺ → Fe³⁺ + e⁻
Iron loses electrons.
Reduction
MnO₄⁻ + 8H⁺ + 5e⁻ → Mn²⁺ + 4H₂O
Manganese gains electrons.
Electrons transferred: 5 e⁻
What is a redox equation?
A redox reaction involves electrons moving from one species to another. Oxidation is the loss of electrons, while reduction is the gain of electrons.
Method
How redox balancing works
The calculator uses the half-reaction method:
Separate oxidation and reduction
Split the equation into two half-reactions.
Balance atoms in each half-reaction
Balance the other elements first. Then balance oxygen with H₂O and hydrogen with H⁺ in acidic solution or OH⁻ in basic solution.
Balance charge with electrons
Add electrons to the more positive side of each half-reaction.
Match electrons and combine
Multiply the half-reactions so the electrons cancel, then add them together.
Acidic vs basic solution
| Aspect | Acidic | Basic |
|---|---|---|
| Oxygen balancing | H₂O | H₂O |
| Hydrogen balancing | H⁺ | OH⁻ |
| Charge balancing | e⁻ | e⁻ |
The solution type matters because acidic and basic reactions use different species to balance hydrogen and oxygen.
A common mistake
Do not change the subscripts inside a chemical formula to balance a reaction. Change the coefficients in front of the formulas instead.
Make sure the solution type matches the reaction conditions. Acidic and basic solutions can produce different balanced equations.
Worked example
Permanganate + iron(II) in acid
Input:
MnO₄⁻ + Fe²⁺ → Mn²⁺ + Fe³⁺
MnO₄⁻ + 5Fe²⁺ + 8H⁺ → Mn²⁺ + 5Fe³⁺ + 4H₂O
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FAQ
Frequently asked questions
What is a redox equation?
A redox equation describes a reaction where electrons are transferred between species.
What is the half-reaction method?
It separates oxidation and reduction into two half-reactions, balances each one, then combines them after matching the electrons.
Should I choose acidic or basic?
Choose the solution type that matches the reaction conditions. The balancing species and final equation can differ between acidic and basic solution.
Do I need to enter H⁺, OH⁻, H₂O, or electrons?
No. Enter the main reaction species. The calculator adds the required balancing species automatically.
Why do I need to balance charge?
A redox equation must conserve both atoms and total electrical charge.
Can I use this for ionic equations?
Yes. Enter the ionic species and their charges, such as MnO₄⁻, Fe²⁺, or Cr₂O₇²⁻.