Balancing chemical equations
High School
Definition
Adjusting the coefficients in a chemical equation so that the same number of atoms of each element appears on both the reactant and product sides. Balancing reflects the law of conservation of mass, since atoms are neither created nor destroyed in a reaction.
Worked examples
\(\)H\(_2 + \)O\(_2 \)→\( \)H\(_2\)O\(\) becomes \(2\)H\(_2 + \)O\(_2 \)→\( 2\)H\(_2\)O\(\)
Add coefficient 2 before H₂ and H₂O so both sides have 4 H atoms and 2 O atoms.
\(\)CH\(_4 + 2\)O\(_2 \)→\( \)CO\(_2 + 2\)H\(_2\)O\(\)
1 C, 4 H, and 4 O on each side — the equation conserves mass and is balanced.
Common mistakes
- \(\)H\(_2 + \)O\(_2 \)→\( \)H\(_2\)O\(_2\) → \(2\)H\(_2 + \)O\(_2 \)→\( 2\)H\(_2\)O\(\) You may only change coefficients, never subscripts — subscripts define the molecules themselves.
- Balance one element and ignore the others. → Check every element appears in equal count on both sides. All atoms must be accounted for to satisfy conservation of mass.
- \(\)N\(_2 + \)H\(_2 \)→\( 2\)NH\(_3\) → \(\)N\(_2 + 3\)H\(_2 \)→\( 2\)NH\(_3\) Recount after each adjustment — forgetting to update all elements leads to unbalanced equations.
Where you'll use it next
Balancing equations is essential for stoichiometry, where you calculate reactant and product masses, determine limiting reagents, and predict yields in chemistry labs and industry.
Found in 1 StudyPug lesson
Balancing Chemical Equations: Your Key to Chemistry Success
11th Grade11thChemistry 11
Unlock the secrets of chemical reactions with our expert guide to balancing equations. Master this crucial skill for academic excellence and real-world applications in science and industry.
See also
Reviewed by Pat Cheng, M.Ed. — StudyPug Curriculum Lead · Last updated June 6, 2026