Guides
How to Balance Chemical Equations — Steps, Tips & Examples
Balancing means making the number of atoms of each element equal on both sides (conservation of mass). You may only change the coefficients in front of formulas — never the subscripts inside them.
Principle
Atoms are neither created nor destroyed (conservation of mass). When balancing you change coefficients, not formulas, and reduce to the simplest whole-number ratio.
Steps & tips
- Start with the complex species Assign a coefficient first to the compound with the most elements or the most complex one.
- Use the LCM For an element with unequal counts, use the lowest common multiple to set coefficients.
- Handle odd counts If an element (often O) is odd on one side, double the species containing it to make it even.
- Check & simplify Verify each element matches on both sides, then reduce all coefficients to the simplest whole-number ratio.
Examples
| Unbalanced | Balanced |
|---|---|
| Fe + O₂ → Fe₃O₄ | 3Fe + 2O₂ → Fe₃O₄ |
| H₂ + O₂ → H₂O | 2H₂ + O₂ → 2H₂O |
| Al + HCl → AlCl₃ + H₂ | 2Al + 6HCl → 2AlCl₃ + 3H₂↑ |
Type any equation into the balancer in the reactions library to balance it instantly and see the coefficients.