Empirical Formulas formaldehyde CH2O (toxic preservative) acetic acid C2H4O2 (vinegar) glucose C6H12O6 (simple sugar) all have the same basic empirical formula CH2O

empirical formula: smallest whole-number ratio of the atoms in a compound. Examples: CH2 OH PbO2 C2H6N Non-Examples: C6H12 H2O2 Pb2O4 C6H18N3

Acetylene (C2H2) is a gas used in welder’s torches. These two compounds of carbon both have the same empirical formula (CH) but different molecular formulas. Styrene (C8H8) is used in making polystyrene.

% composition  empirical formula From To % composition  empirical formula Percent to Mass Mass to Mole Divide by Small Times ‘til Whole assume 100 g g  mol using molar mass to get ratio of atoms no fractions of an atom

What is the empirical formula of a compound that is analyzed and found to contain 25.9% N and 74.1% O? ÷ by Small % to Mass Mass to Mole times ‘til whole 25.9 g N 74.1 g O x 1 mol N 14.01 g N x 1 mol O 16.00 g O = 1.85 mol N = 4.63 mol O ________ 1.85 = 1 N = 2.5 O x 2 = 2 N x 2 = 5 O N2O5

1,6-diaminohexane is used to make nylon 1,6-diaminohexane is used to make nylon. What is the empirical formula if it is 62.1% C, 13.8% H, and 24.1% N? ÷ by Small % to Mass Mass to Mole C3H8N 62.1 g C 13.8 g H 24.1 g N x 1 mol C 12.01 g C x 1 mol H 1.01 g H x 1 mol N 14.01 g N = 5.17 mol C = 13.7 mol H = 1.72 mol N ________ 1.72 _________ = 3 C = 8 H = 1 N

Quick Quiz! 1. An empirical formula shows the __________ of atoms in a compound. lowest common number highest whole number ratio lowest whole number ratio average ratio

Quick Quiz. 2. Which of the following is NOT an empirical formula? CH3 H2N CH C3H6