Computing Empirical Formulas

We are given a percent composition of 20.0% carbon, 2.2% hydrogen, and 77.8% chlorine. Determine the empirical formula of the compound.

Begin by assuming we have 100 g of the compound. Enter the grams of each element in the table below. Compute the moles of each element by dividing the grams of each element by its molar mass in g/mol. (C is 12.01 g/mol; H is 1.008 g/mol; Cl is 35.45 g/mol)

Elements Grams Moles Divide by Smallest Smallest Integers
C 20.0 g 1.67 mol 1.00 3
H 2.2 g 2.2 mol 1.3 4
Cl 77.8 g 2.19 mol 1.31 4
So the empirical formula is C3H4Cl4