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Saturday, September 13, 2014

Empirical and Molecular Formula Problems

Category: Chemical Engineering Math

"Published in Vacaville, California, USA"

Percent composition data for the chlorofluorocarbon Freon-12 by mass are: 9.933% carbon, 58.63% chlorine, and 31.44% fluorine. Based on these data, what is the empirical formula of Freon-12?

Solution:

Basis: 100 grams of sample 

Weight of each components:

      Weight of carbon is


      Weight of chlorine is


      Weight of fluorine is


Moles of each components:

      Moles of carbon is 


      Moles of chlorine is


      Moles of fluorine is


From the number of moles of each component, we need to divide all of them by their least number of moles which is carbon in order to get the number of atoms in a sample.

      Number of carbon in a sample is


      Number of chlorine in a sample is


      Number of fluorine in a sample is


Therefore, the empirical formula for Freon-12 is