Balancing Redox Reactions
- Oxidation numbers can be used to balance chemical equations
- Roman numerals between brackets are used to show the ox. no. of an atom that can have multiple oxidation states, e.g.:
- Fe(II) = iron with an oxidation number of +2
- Fe(III) = iron with an oxidation number of +3
Worked example
Writing overall redox reactions
Manganate(VII) ions, MnO4–, react with Fe2+ ions in the presence of acid, H+, to form Mn2+ ions, Fe3+ ions and water.
Write the overall redox equation for this reaction.
Answer
- Step 1: Write the unbalanced equation and identify the atoms which change in oxidation number:
- Step 2: Deduce the oxidation number changes:
- Step 3: Balance the oxidation number changes:
- Step 4: Balance the charges:
- Step 5: Balance the atoms: