Chemical Equation Balancer

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Step-by-step hints

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Worked example

Step-by-step solution

Balance Fe + O2 -> Fe2O3.

Step 1 / 3

Count atoms in the unbalanced equation

Iron and oxygen counts do not initially match.

\mathrm{Fe}+\mathrm{O_2}\rightarrow\mathrm{Fe_2O_3}

How to use the Chemical Equation Balancer

This Chemical Equation Balancer balances common school and introductory college reactions by changing coefficients while preserving chemical formulas. Provide reactants and products; balancing alone does not establish that a reaction occurs.

Enter the correct reactant and product formulas.
Count each element on both sides of the equation.
Adjust coefficients, never the subscripts inside a formula.
Reduce to the smallest whole numbers and recheck atoms and any charge.

Conservation of atoms

4\mathrm{Fe}+3\mathrm{O_2}\rightarrow2\mathrm{Fe_2O_3}

A balanced equation contains the same number of atoms of each element on each side. Coefficients multiply an entire formula; changing a subscript changes the substance.

For ionic equations, charge must also be conserved. Redox balancing may require a stated acidic or basic medium, and an atom-balanced equation is not evidence of chemical feasibility.

Using the Chemical Equation Balancer to conserve atoms and charge

Keep chemical formulas fixed while changing coefficients

A chemical equation describes specified reactants and products. Balancing asks for coefficients that conserve the atoms in those formulas; it does not permit changing a formula to make the counts convenient. In H2O, the subscript 2 belongs only to hydrogen. A coefficient 3 in front of H2O multiplies the entire formula and therefore represents six hydrogen atoms and three oxygen atoms. Keep element capitalization intact as well: Co denotes cobalt, whereas CO contains carbon and oxygen. Those strings cannot be substituted for each other during balancing.

Start with a table of each element’s count on both sides. Count atoms inside parentheses before multiplying by an outside subscript, then multiply the complete formula by its coefficient. If an equation includes an ion, keep the charge attached to the correct species. The identities of the products must be given or supported by additional reaction information. An equation with an unspecified product cannot generally be completed from atom conservation alone. Several different products may satisfy some conservation constraints while representing different chemistry.

Balance a combustion example and verify every element

For the supplied equation C3H8 + O2 -> CO2 + H2O, first match carbon. One propane formula contains three carbon atoms, so use 3 CO2. Next match hydrogen: eight hydrogen atoms require 4 H2O. The product side then has six oxygen atoms in carbon dioxide and four in water, giving ten oxygen atoms altogether. Five O2 molecules supply those ten atoms. The balanced equation is C3H8 + 5 O2 -> 3 CO2 + 4 H2O, with coefficient ratio 1:5:3:4.

Check the final equation without relying on the balancing sequence. Carbon is three on each side, hydrogen is eight, and oxygen is ten. The coefficients have no common whole-number divisor greater than one, so the ratio is already the conventional smallest positive whole-number ratio. A fraction can be useful during an intermediate balancing step, but scale the entire equation together to remove fractional coefficients. Scaling only one term would change the ratios and break the equality of atom counts that you just established.

Include electric charge in ionic equations

Atoms are not the only conserved quantity in an ionic equation. For the supplied equation Zn + Ag+ -> Zn2+ + Ag, zinc atoms already match, but electric charge does not. Using two silver ions and two silver atoms gives Zn + 2 Ag+ -> Zn2+ + 2 Ag. Each side has one zinc atom and two silver atoms. Total charge is +2 on the left and +2 on the right. This is a conservation calculation for the stated species, not a prediction of experimental conditions.

More complicated redox equations may require water, hydrogen ions or hydroxide ions according to the stated medium. Acidic and basic forms can use different auxiliary species, so the medium is part of the mathematical input. Half-reaction methods track electron transfer and require electrons to cancel when the overall equation is assembled. If charge matches but an element does not, the equation is still unbalanced. If atoms match but charge does not, it is also unbalanced. Verify the complete final equation, not just the elements you adjusted first.

Interpret the coefficients without overreading the result

Coefficients give relative numbers of specified particles or moles. The propane example says that one mole of propane corresponds stoichiometrically to five moles of oxygen, three of carbon dioxide and four of water. These are not direct mass ratios: each substance has its own molar mass. A later yield calculation must use the balanced ratio, convert masses to moles where necessary and identify the limiting reactant. Balancing by itself says nothing about which reactant is available in excess or how much product is actually obtained.

A balanced equation is a necessary conservation statement, not evidence that a proposed reaction occurs under arbitrary conditions. It does not establish reaction rate, equilibrium position, conversion or product purity. If a formula, charge or arrow is unreadable in an uploaded question, supply a clear transcription before drawing numerical conclusions. Keep the final formulas and charges visible when checking a result, and distinguish coefficient changes from subscript edits. These tools explain school and introductory college calculations without providing experimental procedures. AI tools share your existing account allowance; a new standard or deep solve counts against its corresponding solve limit.

Frequently asked questions

Can I change subscripts to balance?

No. Subscripts define the compound. Only coefficients in front of complete formulas can be changed.

Why use whole-number coefficients?

Smallest whole numbers express the relative particle or mole counts conventionally. Fractional intermediate coefficients can be scaled at the end.

Does balancing predict products?

No. Supply the products or explain the reaction conditions. Conservation of atoms alone does not determine which reaction occurs.

What about ionic or redox equations?

Include charges and the reaction medium. Both atom counts and total charge must match, and half-reaction methods may be needed.

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