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Empirical and Molecular Formulas Unit 7 - 2009. Empirical and Molecular Formulas An empirical formula shows the simplest whole number ratio of atoms of.

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Presentation on theme: "Empirical and Molecular Formulas Unit 7 - 2009. Empirical and Molecular Formulas An empirical formula shows the simplest whole number ratio of atoms of."— Presentation transcript:

1 Empirical and Molecular Formulas Unit

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 contd 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 0.18 grams of magnesium react with 0.12 grams of oxygen to form magnesium oxide 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

6 Example An oxide of aluminum is formed with g of Aluminum and g of Oxygen. 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

7 Find 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 g/mol. What is the molecular formula for this compound?


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