How to Use Combustion Analysis Calculator
The Combustion Analysis Calculator converts combustion product masses into element percentages and an empirical formula. Enter the known masses and tick whether the compound contains oxygen.
- Sample mass – The mass of the organic compound burned, in grams.
- Mass of CO₂ produced – The mass of carbon dioxide collected from the combustion, in grams.
- Mass of H₂O produced – The mass of water collected from the combustion, in grams.
- Sample contains oxygen – Enable this option to calculate the oxygen content by mass difference.
- Review the result – The Combustion Analysis Calculator displays the mole calculations, percentages, mole ratios, and empirical formula for C, H, and (optionally) O.
Formula & Theory - Combustion Analysis Calculator
The Combustion Analysis Calculator uses this core formula or rule set from the stoichiometric relationships between combustion products and elements:
n(C) = m(CO₂) / M(CO₂) [since each CO₂ contains one C]
n(H) = 2 × m(H₂O) / M(H₂O) [since each H₂O contains two H]
m(O) = m(sample) − m(C) − m(H) [by mass balance, if O is present]
n(O) = m(O) / M(O)| Symbol | Meaning | Value |
|---|---|---|
| M(CO₂) | Molar mass of CO₂ | 44.01 g/mol |
| M(H₂O) | Molar mass of H₂O | 18.015 g/mol |
| M(C) | Molar mass of C | 12.011 g/mol |
| M(H) | Molar mass of H | 1.008 g/mol |
| M(O) | Molar mass of O | 15.999 g/mol |
After computing moles of each element, divide all values by the smallest to obtain normalised ratios, then multiply through to reach the nearest whole integers — this is the empirical formula.
Assumptions and Limits
- Complete combustion is assumed: all carbon converts to CO₂ and all hydrogen converts to H₂O.
- Elements other than C, H, and O (e.g., N, S, halogens) are not accounted for in this version.
- The mass balance for oxygen is only valid if C and H account for all the discrepancy; otherwise result should be interpreted with caution.
Use Cases for Combustion Analysis Calculator
The Combustion Analysis Calculator is an essential tool for organic chemistry. Common uses include:
- Organic chemistry coursework – Solving combustion analysis problems and checking manual calculations.
- Unknown compound identification – Narrowing down possible structures by establishing the empirical formula.
- Laboratory data processing – Converting measured CO₂ and H₂O masses to elemental percentages.
- Molecular formula derivation – Using the empirical formula as the first step toward finding the full molecular formula with a known molar mass.
The Combustion Analysis Calculator reduces the manual arithmetic and makes the step-by-step reasoning transparent, helping students verify each part of their work.