Redox reactions look chaotic until you realise the secret: oxidation and reduction happen independently, each in their own half-equation. Balance atoms and charge separately, then merge them back together. Drag the slider below to watch electrons flow from one half to the other.
In acidic solution, you balance oxygen atoms by adding water molecules to the side that needs oxygen, then balance hydrogen by adding H⁺ ions to the opposite side. The acid provides an unlimited supply of hydrogen ions, so you can add as many as needed to balance each half-equation. After balancing atoms, you add electrons to balance charge — the side with more positive charge gets electrons. This works because the acidic environment naturally contains excess H⁺ ions that participate in the reaction mechanism.