Combustion Reaction Products Calculator

Combustion Reaction Products Calculator: Full Molar Breakdown of Combustion Gases

Beyond simply balancing the reaction, this calculator determines the actual molar quantities of every major combustion product, including excess oxygen and the accompanying nitrogen, when a hydrocarbon fuel is burned with a specified excess air margin.

The Formula

CO2 = x, H2O = y/2, Excess O2 = (x + y/4) × Excess Air% / 100, N2 = Actual O2 × (79/21)

Worked Example

Methane (x=1, y=4) burned with 15% excess air:

CO2 = 1 mol, H2O = 2 mol, Excess O2 = 2 × 0.15 = 0.3 mol, N2 = 2.3 × (79/21) = 8.65 mol

How to Use This Calculator

1. Enter the carbon and hydrogen atom counts for the fuel formula CxHy.
2. Optionally enter the excess air percentage (0 for exact stoichiometric).
3. Click Calculate to get the full molar breakdown of combustion products.

Related Calculations

Use with the Exhaust Gas Composition Calculator to convert these molar quantities into mass percentages.