Combustion Reaction Calculator

Combustion reactions describe what happens when a fuel burns in oxygen — the Combustion Reaction Calculator balances the chemical equation for any hydrocarbon or alcohol fuel automatically. Enter a fuel formula (such as CH4, C3H8, or C2H5OH) and select your calculation mode to get the balanced equation, along with moles of oxygen needed, CO₂ produced, and H₂O produced. Optionally enter a fuel amount in moles to scale all outputs, or check Include Nitrogen to model air-based combustion.

Enter chemical formula like CH4, C3H8, or C2H5OH

mol

Amount of fuel for calculation (only used in amounts mode)

Include N₂ from air in the balanced equation

Results

Balanced Equation

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Oxygen Needed

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CO₂ Produced

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H₂O Produced

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Fuel Coefficient

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O₂ Coefficient

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Frequently Asked Questions

How do you balance combustion reactions?

To balance a combustion reaction, first identify the fuel (hydrocarbon) and write the general form: Fuel + O₂ → CO₂ + H₂O. Then balance carbon atoms first, hydrogen atoms second, and oxygen atoms last by adjusting coefficients.

What is a combustion reaction?

A combustion reaction is a chemical reaction where a fuel (usually containing carbon and hydrogen) reacts with oxygen to produce carbon dioxide and water, releasing energy in the form of heat and light.

What are common examples of combustion reactions?

Common examples include methane combustion (CH₄ + 2O₂ → CO₂ + 2H₂O), propane combustion (C₃H₈ + 5O₂ → 3CO₂ + 4H₂O), and ethanol combustion (C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O).

How do you calculate oxygen needed for complete combustion?

For a hydrocarbon CₐHᵦOᵧ, the oxygen coefficient is (2a + b/2 - γ)/2. This ensures complete combustion where all carbon becomes CO₂ and all hydrogen becomes H₂O.

What is the difference between complete and incomplete combustion?

Complete combustion occurs with sufficient oxygen, producing only CO₂ and H₂O. Incomplete combustion occurs with limited oxygen, producing carbon monoxide (CO), carbon (soot), and other partial oxidation products.

Why do we need to balance chemical equations?

Chemical equations must be balanced to obey the law of conservation of mass - atoms cannot be created or destroyed in a chemical reaction, so the same number of each type of atom must appear on both sides.

Can this calculator handle oxygen-containing fuels?

Yes, this calculator can balance combustion reactions for fuels containing carbon, hydrogen, and oxygen atoms, such as alcohols (C₂H₅OH) and organic acids. The oxygen in the fuel reduces the amount of O₂ needed.

What does the nitrogen option do?

When nitrogen is included, the calculator accounts for N₂ from air (air is ~79% N₂, 21% O₂). This gives a more realistic representation of combustion in air rather than pure oxygen.