Chemistry 11 · Chemistry · Lesson 5.2
Balancing chemical equations
- Level
- Grade 11
- Reading time
- 11 min reading
- Review
- Last reviewed 2026-09-03
- Standard
- Accuracy standard
- Errata
Abstract
Balancing by inspection, step by step.
How do you balance a chemical equation?
Short answer
Balancing a chemical equation means adjusting the coefficients so that each element has the same number of atoms on both sides, satisfying conservation of mass. You change only the coefficients (never the subscripts in a formula), usually balancing the most complex molecule first and leaving free elements for last, then checking every atom.
Concept preview
What you will be able to do
- 01Explain why balancing is required by conservation of atoms
- 02Balance an equation by adjusting coefficients
- 03Balance groups, diatomic elements and fractional coefficients
Because atoms are conserved, a correct equation must have the same number of each kind of atom on both sides — it must be balanced. You balance ONLY by placing coefficients in front of formulas; you never change the subscripts, because that would change the identity of a substance. An unbalanced equation such as has three oxygens on the left and one on the right and so cannot be correct.
School Plan
Balancing chemical equations
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Related topics
Frequently asked questions
- Why can’t you change subscripts to balance an equation?
- Subscripts define the substance itself. Changing them changes what the compound is; only coefficients (amounts) may be adjusted.
- What does a balanced equation tell you?
- The mole ratio in which substances react and are produced — the basis for all stoichiometry calculations.