How to Balance Chemical Equations (and Check the Atoms)
Balancing equations is one of those Class 9 and 10 chemistry skills that seems easy with water and turns painful with something like the combustion of octane or a redox reaction with ions. Chemical equation balancer finds the smallest whole-number coefficients and, importantly for learning, shows the equation for each element so you can see why the answer works.
Steps
- Enter the equation with one arrow, such as
H2 + O2 -> H2O. - Read the atom equations, one row per element.
- Use the coefficients in the balanced equation, then look at the atom check.
How it finds the balance
Each formula is broken into elements, with parentheses, brackets, charges and hydrate dots all counted. The page writes one equation per element, plus a charge equation if any species is charged. Then it finds the smallest positive whole numbers that satisfy all of them at once. Mathematically, it's a system of linear equations, which is also the most reliable way to balance by hand for tricky reactions.
The classic: H2 + O2 -> H2O becomes 2 H2 + O2 -> 2 H2O.
What you can type
- Parentheses and brackets:
Ca(OH)2,Fe2(SO4)3. - Charges:
Fe3+,OH−; the charge is balanced along with the atoms. - Electrons: write
e−for half-equations. - Hydrates:
CuSO4·5H2O. - States like
(s),(l),(g),(aq)are fine; they're ignored since they don't change the atom count.
If you type coefficients yourself, they're recalculated, so a 2 you already put in front of H2O gets replaced by the correct value.
Using it to learn, not just to get answers
The atom equations are the useful part for students. Try balancing by hand first, then compare. If you got it wrong, look at which element's row doesn't add up. That tells you where your method slipped.
A good hand method for tough ones:
- Start with the element that appears in the fewest formulas.
- Leave hydrogen and oxygen until last.
- Balance polyatomic ions (like SO4) as a single unit if they appear unchanged on both sides.
- Multiply through to clear fractions at the end.
Worked example: burning propane
C3H8 + O2 -> CO2 + H2O. Carbon: 3 CO2. Hydrogen: 8 H means 4 H2O. Oxygen on the right: 6 + 4 = 10 atoms, so 5 O2. Result: C3H8 + 5 O2 -> 3 CO2 + 4 H2O. Type it in and the page agrees, with each element's count shown on both sides.
When it won't balance
If no set of whole numbers conserves every atom, the working stops. That almost always means a typo in a formula (Na2Cl instead of NaCl), a species on the wrong side, or a missing product. Check the formulas against your textbook.
Why balancing matters at all
A balanced equation is a statement of the law of conservation of mass: atoms aren't created or destroyed in a chemical reaction, only rearranged. The coefficients also give the mole ratios you need for stoichiometry: how many grams of oxygen burn a given mass of fuel, or how much product a reaction can yield. Get the balancing wrong and every calculation that follows is wrong too, which is why examiners award marks for it separately.
Privacy
According to the page, everything runs in the page and stays on your device. Google ads appear on the page, as on the rest of the site.
FAQ
How does water balance?
2 H2 + O2 -> 2 H2O, with coefficients 2, 1 and 2.
Can I use parentheses and charges? Yes, and hydrates too.
What if it won't balance? Check the formulas and which side each is on.
Do I need to include coefficients? No; any you type are recalculated.
Check your homework, and your method, with Chemical equation balancer.
— Alok Kumar Singh