Redox Half-Reaction Balancer
Water, protons and electrons, in the right order.
Water, protons and electrons, in the right order. Shows the working, not just the answer.
In MnO₄⁻ → Mn²⁺, that is 4 on the left and 0 on the right.
Before adding any H⁺ — just what is in the formulas.
Electrons gained (reduction)
5 e⁻
4 H₂O, 8 H⁺ · Acidic solution
The order matters and it is always the same: balance the element being oxidised or reduced, then oxygen with water, then hydrogen with H⁺, then charge with electrons. Doing charge before hydrogen gives the wrong electron count, because every H⁺ added carries a charge of its own. In basic solution, balance it as if acidic and then add the same number of OH⁻ to BOTH sides. The OH⁻ and H⁺ on one side combine into water, and any water appearing on both sides cancels down. To combine two half-reactions, multiply each so the electron counts match, then add. The electrons must cancel completely — if they do not, one half-reaction is wrong.
How the Redox Half-Reaction Balancer works
Enter the atom and charge counts on each side and this works out how much water, how many protons and how many electrons to add, in the order that actually works. Basic solution is handled by neutralising afterwards, as the method requires.
Also known as: balancing redox reactions calculator · half reaction method calculator · how to balance redox equations · redox balancer for basic solution
Frequently asked questions
How do I balance a half-reaction?
In this order: the element being oxidised or reduced, then oxygen with water, then hydrogen with H⁺, then charge with electrons. The order is not optional — doing charge before hydrogen gives the wrong electron count.
How is basic solution different?
Balance it as though acidic, then add the same number of OH⁻ to both sides. The OH⁻ meets the H⁺ and becomes water, and any water on both sides cancels down.
Why does the order matter?
Because each step changes what the next one sees. Adding water brings hydrogen with it, and adding H⁺ brings charge with it. Balancing charge first means balancing it against a count that is about to change.
How do I combine two half-reactions?
Multiply each one so the electron counts match, then add them. The electrons must cancel exactly — if any are left over on either side, one of the half-reactions is wrong.
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