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The ChemCollective >> Stoichiometry Tutorials>> Empirical Formula from Molecular Formula

Stoichiometry Tutorials: Part 11 - Determining the Empirical Formula of a Compund from Its Molecular Formula (from a complete OLI stoichiometry course)

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.

 

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   Page Last Updated: 02.16.2011