How this calculator works
Assume all carbon is recovered as CO2 and all hydrogen as H2O. Their known mass fractions give carbon and hydrogen in the original sample. For a CHO sample, oxygen is the mass left over. For a CH sample, recovered masses must close within 0.5%. The formula search uses the same small-ratio tolerance as the empirical formula tool.
Formula
mC = mCO2 x 12.011/44.009; mH = mH2O x 2.016/18.015; mO = msample - mC - mH.
Worked example
A 30.026 g CHO sample giving 44.009 g CO2 and 18.015 g water contains 12.011 g C, 2.016 g H and 15.999 g O, hence CH2O.
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Frequently asked questions
Why is product mass greater than sample mass?
Oxygen supplied during combustion contributes to the collected CO2 and water.
Can the sample contain nitrogen?
No. Oxygen by difference is valid here only for a sample known to contain C, H and O.
Does this determine isomers?
No. Combustion composition gives formulas, not atom connectivity.