Combustion analysis is commonly used to determine the percent composition of carbon and hydrogen in a sample of a pure compound. Oxygen can not be determined by combustion analysis, and is usually estimated by difference. Other elements such as nitrogen, chlorine and sulfur can be measured directly in other ways.
An empirical formula is derived from the elemental composition of a compound. It represents the simplest whole number ratio of the different kinds of atoms that make up a molecule of a given compound. The molecular formula of a compound gives the actual number of the different atoms in a molecule. To convert an empirical formula into a molecular formula a molecular weight measurement is needed.
The elemental order in such formulas is: CHOZ, where Z = other elements. Do not try to subscript numbers. For question VI enter two or more letters or X for none.