Combustion Analysis Calculator
Determine the empirical formula of a C, H, O compound from combustion data. Enter the masses of sample, CO₂ produced, and H₂O produced.
Mass of the unknown organic compound sample
Mass of carbon dioxide produced from combustion
Mass of water produced from combustion
Mass of oxygen consumed (if compound contains oxygen)
What is combustion analysis?
Combustion analysis (elemental analysis) burns an organic compound in excess oxygen to produce CO₂, H₂O, and possibly N₂. By measuring the masses of CO₂ and H₂O produced, we can determine the empirical formula: mass of C = mass(CO₂) × (12.01/44.01), mass of H = mass(H₂O) × (2.016/18.015).
How do you determine if oxygen is present?
Sum the masses of C and H found. If this is less than the original sample mass, the difference is oxygen: mass(O) = mass(sample) - mass(C) - mass(H). If the sum equals the sample mass, the compound contains only C, H (and possibly N, which requires separate analysis).
How do you find the empirical formula?
1) Calculate masses of C, H, O from combustion data, 2) Convert to moles (÷ atomic mass), 3) Divide all by the smallest mole value, 4) Multiply to get whole numbers. Example: C=4.36mg→0.363mmol, H=0.73mg→0.73mmol, ratio C:H = 1:2 → CH₂.
What is the difference between empirical and molecular formula?
Empirical formula is the simplest whole-number ratio of atoms (e.g., CH₂O for glucose). Molecular formula is the actual number of atoms (C₆H₁₂O₆ for glucose). To get molecular formula, divide the molar mass by the empirical formula mass: n = Molar Mass / Empirical Mass.