empirical and molecular formulas - edl · empirical formula calculations reverse of percent...
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Empirical and Molecular FormulasTextbook Section 7.4
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Today’s Learning Target
1. Determine the empirical formula given percent data.
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Empirical Formula
Definition: Formula with the lowest whole-number ratio between the elements
Examples:
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Empirical Formula Calculations
Reverse of Percent Composition:
1. Change percent signs to grams.2. Using PT, convert grams to moles.3. Divide by the smallest number of moles.4. Will give you the lowest ratio between the elements.
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Empirical Formula Examples
1. Determine the empirical formula of the compound that contains 17.15% carbon, 1.44% hydrogen and 81.41% fluorine.
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Empirical Formula Examples
2. Determine the empirical formula for the compound that is 40.00% C, 6.72% H, and 53.29% O.
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HOMEWORK
Worksheet Questions 1-4, 10
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Today’s Learning Target
1. Determine the molecular formula given the molar mass and empirical formula.
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Molecular Formula
Definition: Formula showing the actual number of each element present in the compound.
To Calculate, need two things:
1. empirical formula2. molar mass of compound [given in problem]
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Molecular Formula Examples
1. Determine the molecular formula of a compound with an empirical formula of NH2 and a molar mass of 32.06 g/mol.
2. The empirical formula of hexane is C3H7. It’s molar mass is 86.2 g/mol. What is the molecular formula?
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Combining the Two
Caffeine is 49.5% C, 5.15% H, 16.5% O and 28.9% N by mass. From this data calculate the empirical formula. The molar mass of the compound is known to be 194.2 g/mol; determine the molecular formula for caffeine.
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HOMEWORK
FINISH WORKSHEET