Empirical Formulas formaldehyde CH 2 O (toxic preservative) acetic acid C 2 H 4 O 2 (vinegar) glucose C 6 H 12 O 6 (simple sugar) all have the same basic or “empirical” formula CH 2 O

empirical formula: smallest whole-number ratio of the atoms in a compound. Examples: CH 2 HOPbO 2 C 2 H 6 N Non-Examples: C 6 H 12 H 2 O 2 Pb 2 O 4 C 6 H 18 N 3

Acetylene (C 2 H 2 ) 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 (C 8 H 8 ) is used in making polystyrene.

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

= 1.85 mol N = 4.63 mol O ________ 1.85 ________ 1.85 What is the empirical formula of a compound that is analyzed and found to contain 25.9% N and 74.1% O? 25.9 g N 74.1 g O x 1 mol N g N x 1 mol O g O = 1 N = 2.5 O x 2 = 2 N x 2 = 5 O N2O5N2O5 % to MassMass to Mole times ‘til whole

62.1 g C 13.8 g H 24.1 g N x 1 mol C g C x 1 mol H 1.01 g H x 1 mol N g N = 5.17 mol C = mol H = 1.72 mol N ________ 1.72 _________ 1.72 ________ 1.72 = 3 C = 8 H = 1 N C3H8NC3H8N 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? % to MassMass to Mole

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

2. Which of the following is NOT an empirical formula? A.CH 3 B.H 2 N C.CH D.C 3 H 6 Quick Quiz.