2Empirical 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
3Example: Glucose Glucose has a molecular formula of: C6H12O6It has an empirical formula of:CH2O
4Formulas cont’dA molecular formula is always a multiple of empirical formulaA compound has ONE molecular formulaMany compounds have the same empirical formula
5Example0.18 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
6ExampleAn 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
7Find 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?