Balancing Chemical Equations
Simple Explanation
A balanced chemical equation has the same number of each type of atom on both sides, since atoms are never created or destroyed in a chemical reaction. You balance an equation by adjusting the numbers in front of each formula (coefficients) — never the subscripts within a formula.
Why Do We Need It?
An unbalanced equation would imply atoms appearing from nowhere or vanishing — balancing is how a chemical equation obeys the law of conservation of mass.
Worked Example
Balance a combustion equation
Balance the equation: H₂ + O₂ → H₂O
Why Does This Work?
Because atoms can't be created or destroyed, the same total of each element must appear on both sides — adjusting coefficients (never subscripts) is the only way to change atom counts without changing what substances are actually involved.
Real-Life Example
Calculating fuel and oxygen needed for combustion
Engineers need a balanced combustion equation to calculate exactly how much oxygen a fuel needs to burn completely.
A balanced equation is what makes it possible to calculate exact reacting quantities, whether for a car engine or a rocket.
Practice
Which coefficients correctly balance: __N₂ + __H₂ → __NH₃?
MediumCommon mistake
Changing the subscripts within a formula (e.g. turning H₂O into H₂O₂) to try to balance an equation — this actually changes the substance being described, not just the amount of it.
Quick Review
- Atoms are conserved: same totals on both sides of the equation.
- Balance using coefficients in front of formulas, never subscripts inside them.
- Recheck every element after each change.