Science & Lab Tools
Combustion Analysis Calculator
Calculate the molecular composition and empirical formula of organic compounds using combustion analysis data.
Reviewed by the calculator.uk.com Team · Last reviewed 3 July 2026 · Our methodology
Enter the mass values to calculate composition
Related to Combustion Analysis Calculator
The Combustion Analysis Calculator determines the empirical formula and elemental composition of organic compounds containing carbon, hydrogen, and oxygen. The calculation process involves analyzing the products of complete combustion (CO₂ and H₂O) and using stoichiometric relationships to determine the original composition.
Calculation Process
1. Carbon content is calculated from CO₂ mass using the ratio of atomic masses (12.01/44.01)
2. Hydrogen content is determined from H₂O mass using the ratio (2.016/18.015)
3. Oxygen content is calculated by subtracting C and H percentages from 100%
4. The empirical formula is derived by converting mass percentages to molar ratios
Key Assumptions
- Complete combustion of the sample
- Only C, H, and O are present in the compound
- All carbon converts to CO₂
- All hydrogen converts to H₂O
The calculator provides both the percentage composition of each element and the empirical formula of the compound. Understanding these results helps in determining the compound's identity and chemical properties.
Percentage Composition
The percentages show the mass contribution of each element to the total compound mass. These values should sum to 100% and provide insight into the compound's composition and potential chemical properties.
Empirical Formula
The empirical formula represents the simplest whole-number ratio of atoms in the compound. For example, CH₂O indicates one carbon atom, two hydrogen atoms, and one oxygen atom in the simplest ratio.
1. What is combustion analysis used for?
Combustion analysis is a fundamental technique in organic chemistry used to determine the elemental composition of unknown organic compounds. It helps identify compounds, verify synthesis products, and ensure material purity.
2. Why might my percentages not add up to exactly 100%?
Small variations from 100% can occur due to experimental error, measurement precision, or the presence of trace elements. Generally, variations within ±1% are considered acceptable in practical applications.
3. What's the difference between empirical and molecular formula?
The empirical formula shows the simplest whole-number ratio of atoms, while the molecular formula shows the actual number of atoms in one molecule. For example, glucose has an empirical formula of CH₂O but a molecular formula of C₆H₁₂O₆.
4. How accurate is combustion analysis?
Modern combustion analysis can be highly accurate, typically achieving precision within ±0.3% for each element. However, accuracy depends on proper sample preparation, complete combustion, and precise measurement of combustion products.
5. What is the scientific source for this calculator?
Determining empirical formulas from combustion data is classic quantitative analytical chemistry - converting measured masses of CO2 and H2O produced during combustion back into moles of carbon and hydrogen in the original sample. The approach is standard material in analytical and organic chemistry references such as Harris's Quantitative Chemical Analysis. Atomic mass values used in the conversion follow IUPAC's standard atomic weights.