OneTaskBy Tim King · Updated
Chemical Equation Balancer
Whole-Number Coefficients With Brackets, Hydrates and Ionic Charges
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How the Chemical Equation Balancer works
This chemical equation balancer finds the smallest whole-number coefficients that make every atom add up on both sides of a reaction. Type the reactants and products separated by = or ->, such as C3H8 + O2 = CO2 + H2O. It handles brackets, hydrates and ionic charges, then shows the coefficients and checks that mass is conserved.
Atoms are not created or destroyed in a chemical reaction, so a correct equation has the same number of each kind of atom on both sides. Balancing means choosing how many of each molecule take part. Only the coefficients in front change; the formulas themselves stay fixed.
How the chemical equation balancer works
The calculator writes one equation for every element: the atoms of that element on the left, times their unknown coefficients, must equal those on the right. Charge gets its own equation when ions are present. It solves this system exactly with fractions, then scales to the smallest whole numbers. The formula behind every line is Σ (coefficient × atoms) left = Σ (coefficient × atoms) right.
First example. Propane burning, C3H8 + O2 = CO2 + H2O. Three carbons give 3 CO₂, eight hydrogens give 4 H₂O, and the 10 oxygen atoms on the right need 5 O₂: C₃H₈ + 5 O₂ → 3 CO₂ + 4 H₂O.
Second example. Aluminium in copper sulfate, Al + CuSO4 = Al2(SO4)3 + Cu, balances to 2 Al + 3 CuSO₄ → Al₂(SO₄)₃ + 3 Cu.
How many oxygen molecules does one methane need to burn? Two: CH₄ + 2 O₂ → CO₂ + 2 H₂O.
Balanced equations for common reactions
| Reaction | Balanced equation |
|---|---|
| Water formation | 2 H₂ + O₂ → 2 H₂O |
| Rusting of iron | 4 Fe + 3 O₂ → 2 Fe₂O₃ |
| Methane combustion | CH₄ + 2 O₂ → CO₂ + 2 H₂O |
| Propane combustion | C₃H₈ + 5 O₂ → 3 CO₂ + 4 H₂O |
| Octane combustion | 2 C₈H₁₈ + 25 O₂ → 16 CO₂ + 18 H₂O |
| Glucose respiration | C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O |
| Photosynthesis | 6 CO₂ + 6 H₂O → C₆H₁₂O₆ + 6 O₂ |
| Ethanol combustion | C₂H₅OH + 3 O₂ → 2 CO₂ + 3 H₂O |
| Haber process | N₂ + 3 H₂ → 2 NH₃ |
| Limestone decomposition | CaCO₃ → CaO + CO₂ |
| Neutralisation | HCl + NaOH → NaCl + H₂O |
| Sulfuric acid and sodium hydroxide | H₂SO₄ + 2 NaOH → Na₂SO₄ + 2 H₂O |
| Zinc in acid | Zn + 2 HCl → ZnCl₂ + H₂ |
| Thermite | 2 Al + Fe₂O₃ → Al₂O₃ + 2 Fe |
| Baking soda and vinegar | NaHCO₃ + CH₃COOH → CH₃COONa + H₂O + CO₂ |
| Hydrogen peroxide decomposition | 2 H₂O₂ → 2 H₂O + O₂ |
| Aluminium oxide | 4 Al + 3 O₂ → 2 Al₂O₃ |
| Potassium chlorate | 2 KClO₃ → 2 KCl + 3 O₂ |
| Silver chloride precipitate | AgNO₃ + NaCl → AgCl + NaNO₃ |
| Phosphoric acid and lime | 3 Ca(OH)₂ + 2 H₃PO₄ → Ca₃(PO₄)₂ + 6 H₂O |
| Copper and nitric acid | 3 Cu + 8 HNO₃ → 3 Cu(NO₃)₂ + 2 NO + 4 H₂O |
| Permanganate and hydrochloric acid | 2 KMnO₄ + 16 HCl → 2 KCl + 2 MnCl₂ + 5 Cl₂ + 8 H₂O |
| Ammonia oxidation | 4 NH₃ + 5 O₂ → 4 NO + 6 H₂O |
| Iron ore smelting | Fe₂O₃ + 3 CO → 2 Fe + 3 CO₂ |
Tips and pitfalls
- Write correct formulas first. The balancer cannot fix H2O written as HO; changing a formula changes the substance.
- Ions need charges. Write them after the formula with a caret or brackets, such as Fe^3+ or MnO4^-, and use e- for electrons in half-equations.
- Diatomic elements. Hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine and iodine are H2, N2, O2, F2, Cl2, Br2 and I2 as free elements.
- Some reactions have many answers. If two independent reactions are mixed together, there is no single balance and the calculator says so.
FAQ
How do you balance a chemical equation?
Count the atoms of each element on both sides, then adjust the numbers in front of each formula until every element matches. Start with the element in the fewest compounds and leave hydrogen and oxygen until last. The balancer does this with algebra, which always works.
Why do chemical equations need to be balanced?
Matter is conserved in chemical reactions, so the same atoms must appear before and after. A balanced equation also gives the mole ratios between substances, which you need to work out how much product a reaction makes or how much of one reactant uses up another.
Can it balance ionic and redox equations?
Yes. Add charges after formulas, such as Cu^2+ or SO4^2-, and include e- for electrons. The calculator adds a charge balance equation alongside the atom balances, so half-equations and net ionic equations come out with both atoms and charge matching.
What does a coefficient mean?
A coefficient is the number in front of a formula. It says how many molecules or moles of that substance take part. In 2 H₂ + O₂ → 2 H₂O, two moles of hydrogen react with one mole of oxygen to give two moles of water.
Why does the balancer say the equation cannot be balanced?
Usually an element appears on only one side, often from a typo such as Co for cobalt instead of CO for carbon monoxide. Check each formula's capital letters and that every product contains only elements from the reactants.
See also: all Chemistry tools, Physics, Electronics.
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