2 Empirical and Molecular Formulas An empirical formula shows the simplest whole number ratio of atoms of each element in a compoundA molecular formula shows the actual number of atoms of each element in a compound
3 Example: Glucose Glucose has a molecular formula of: C6H12O6It has an empirical formula of:CH2O
4 Formulas cont’dA molecular formula is always a multiple of empirical formulaA compound has ONE molecular formulaMany compounds have the same empirical formula
5 Example0.18 grams of magnesium react with 0.12 grams of oxygen to form magnesium oxideConvert all grams to molesDivide all numbers of moles by the smallest # present (do a ratio!)Multiply all numbers by the smallest # that will make them WHOLE NUMBERS
6 ExampleAn oxide of aluminum is formed with g of Aluminum and g of Oxygen. Calculate the empirical formula of the compound:Convert all grams to molesDivide all numbers of moles by the smallest # present (do a ratio!)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 P2O5. It has a molar mass of g/mol. What is the molecular formula for this compound?