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Chemical Equation Balancer
Enter the complete equation — reactants AND products — without worrying about the coefficients. The tool then finds the coefficients that conserve every atom.
To obtain 2 H₂ + O₂ → 2 H₂O, enter
H2 + O2 -> H2O. If you only know H2 + O2 and want to know what product may form, use Complete a reaction.What exactly should you enter?
The balancer does not determine what products will form. It starts from a reaction you already know, but whose coefficients are missing or incorrect. Enter the reactants on the left, an arrow ->, then the products on the right.
It never changes subscripts inside formulas. Changing H₂O into H₂O₂ would create a different substance. Balancing only adds numbers in front of formulas.
H₂ + O₂ → H₂O
1. Input: H2 + O2 -> H2O.
2. Before balancing: H is already 2 on both sides, but O is 2 on the left and 1 on the right.
3. Put 2 before H₂O: this creates 4 H on the right, so put 2 before H₂ as well.
4. Result: 2 H₂ + O₂ → 2 H₂O. H: 4 = 4; O: 2 = 2.
Fe + O₂ → Fe₂O₃
Fe₂O₃ contains 2 Fe and 3 O. The smallest oxygen count compatible with both O₂ and Fe₂O₃ is 6, so use 3 O₂ and 2 Fe₂O₃. This then requires 4 Fe.
Result: 4 Fe + 3 O₂ → 2 Fe₂O₃.
Only know H₂ + O₂?
Then the product is still missing. That is a reaction-completion problem, not only a balancing problem. Use Complete a chemical reaction and enter only H2 + O2.
For ionic equations, write charges with ^, for example Fe^2+, and keep spaces around + signs that separate species. Charge is then balanced together with atoms.