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.

Grade 11 · Chemistry

Balancing chemical equations

Why it matters

Balancing by inspection, step by step.

Core20m readingPrerequisite: Equations and the conservation laws

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.

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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.

How do you balance a chemical equation?

Related topics

Frequently asked questions