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Date ____________________
6 Problems Worksheet – Empirical and Molecular Formulas
1. What is the empirical formula for a compound which contains 53.73 % Fe
and
46.27 % S?
2. What is the empirical formula of a compound which contains 15.77 %
aluminum,
28.11 % sulfur, and 56.12 % oxygen?
3. An organic compound is found to contain 92.25 % carbon and 7.75 %
hydrogen. If the molecular mass is 78 g/mol, what are its empirical and
molecular formulas?
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4. The molecular mass of a compound is 92 g/mol. Analysis of this compound
shows that there are 0.608 g of nitrogen and 1.388 g of oxygen. What are its
empirical and molecular formulas?
5. There are two oxides of phosphorus. Both oxides can exist in different forms
depending on the temperature and pressure. Calculate the empirical and
molecular formulas from the data:
(a) P: 56.4 %
O: 43.7 %
molecular mass: 220 g/mol
(b) P:
43.6 %
O:
56.4%
molecular mass:
284 g/mol
6. A fat is composed of long chains of carbon and hydrogen atoms. In a
reaction with a strong base, a fat forms a soap and glycerol. What is the
empirical formula of a fat containing 77.60 % carbon, 11.45 % oxygen, and
10.95 % hydrogen? What is its molecular formula if its molecular mass is
1253 g/mol?
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7. Magnesium chloride forms a hydrated salt. When a sample of magnesium
chloride is analyzed, it is found to contain 53.20 % water. Calculate the
formula of this hydrate.
8. A hydrated sodium salt containing 39.7 % water is analyzed as follows: Na
16.9 %;
C 17.7 %; H 6.67 %; and O 58.8 %. What is the formula of this salt?