Combustion Analysis Calculator

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Choose C/H if the compound contains no oxygen or nitrogen. Choose C/H/O to derive oxygen by mass difference. Choose C/H/O/N if you also collected the NO2 combustion product.
Mass of the organic compound burned. Required for C/H/O and C/H/O/N modes.
g
Mass gain of the CO₂ absorption trap (ascarite or NaOH).
g
Mass gain of the water absorption trap (magnesium perchlorate or CaCl₂).
g
Known molar mass from mass spectrometry or colligative methods. If provided, the molecular formula is also calculated.
g/mol
Empirical formula
CH2O

Smallest whole-number atomic ratio

Molecular formulaC3H6O3
Empirical formula mass30.026g/mol
Molecular/empirical ratio (n)3
Carbon mass5.1697g
Hydrogen mass0.8672g
Oxygen mass6.8782g
% Carbon0.4%
% Hydrogen0.07%
% Oxygen0.53%
Carbon (g)5.1697
Hydrogen (g)0.8672
Oxygen (g)6.8782
Nitrogen (g)-

Empirical formula: CH2O, molecular formula: C3H6O3.

  • The empirical formula mass is 30.026 g/mol.
  • The molecular formula C3H6O3 is 3 times the empirical unit.
  • Percent composition: C: 40.0%, H: 6.7%, O: 53.3%.
  • Combustion analysis identifies empirical composition only; isomers with the same formula require additional spectroscopic data.

Next stepConfirm the molecular formula with mass spectrometry (EI or ESI-MS) or use colligative properties to measure the molar mass independently.

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