Elemental analysis is a useful qualitative analysis technique since it allows us to check if a sample is consistent with a given molecular formula. For instance, suppose we believe our sample is benzene (C₆H₆). We can compare the following:

The empirical formula (CH) obtained from the molecular formula of benzene (C₆H₆)
The empirical formula obtained from a elemental analysis of the sample

If the two empirical formulae do not agree, then the sample is not benzene. If the formulae agree, then our sample may be benzene. (Remember that more than one molecule can have the sample empirical formula. For instance, both benzene (C₆H₆) and acetylene (C₂H₂) have the empirical formula CH, so a sample whose elemental analysis yields CH as an empirical formula could be benzene, acetylene, or some other molecule with a 1:1 ratio between C and H.)

On this page, we consider the first of the above two bullets: how to determine the empirical formula from the molecular formula. The second bullet is discussed in the next tutorial.

Text version of this movie.

These tutorials are part of a set of equilibrium materials developed with the Open Learning Initiative at Carnegie Mellon University. To access the entire course, please see http://www.cmu.edu/oli/courses/enter_chemistry.html.

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