1. Empirical and Molecular Formulas 2011

2. Empirical and Molecular Formulas An empirical formula shows the simplest whole number ratio of atoms of each element in a compound A molecular formula shows the actual number of atoms of each element in a compound

3. Example: Glucose Glucose has a molecular formula of: – C 6 H 12 O 6 It has an empirical formula of: – CH 2 O

4. Formulas cont’d A molecular formula is always a multiple of empirical formula A compound has ONE molecular formula Many compounds have the same empirical formula

5. Example An compound contains 28.4g of copper and 71.6g of bromine. Calculate the empirical formula of the compound: 1.Convert all grams to moles 2.Divide all numbers of moles by the smallest # present (do a ratio!) 3.Multiply all numbers by the smallest # that will make them WHOLE NUMBERS

6. Example What is the empirical formula for a compound that contains: 77.3% Silver, 7.4% phosphorous and 15.3% O? Convert all grams to moles Divide all numbers of moles by the smallest # present (do a ratio!) Multiply all numbers by the smallest # that will make them WHOLE NUMBERS

7. Example What is the empirical formula for a compound that contains 5.51 g of cobalt and 4.49 g of sulfur? Convert all grams to moles Divide all numbers of moles by the smallest # present (do a ratio!) Multiply all numbers by the smallest # that will make them WHOLE NUMBERS

8. Molecular formulas from empirical formulas A white powder is analyzed and found to have an empirical formula of P 2 O 5. It has a molar mass of 283.88 g/mol. What is the molecular formula for this compound?