How to Balance Chemical Equations in 3 Steps
Balance chemical equations with two worked examples and the subscript mistake to avoid.
The method
- Same number of each atom on both sides
- Change coefficients only, never subscripts
Count atoms, balance one element at a time, then recount.
Example 1
Balance H₂ + O₂ → H₂O
- O: 2 on the left, 1 on the right, so put 2 in front of H₂O
- H: now 4 on the right, so put 2 in front of H₂
2H₂ + O₂ → 2H₂O
Example 2
Balance Fe + O₂ → Fe₂O₃
- O: 2 and 3 → lowest common multiple is 6, so 3O₂ and 2Fe₂O₃
- Fe: 4 on the right, so put 4 in front of Fe
4Fe + 3O₂ → 2Fe₂O₃
Common mistake
H₂ + O₂ → H₂O₂
Changing a subscript changes the substance: H₂O₂ is hydrogen peroxide, not water.
Only coefficients are yours to change.
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