Chem CatalystCalculate the percent composition of ibuprofen (C13H18O2)

Today’s Agenda:1. Catalyst2. Finish Notes- Empirical Formula3. Practice Problems4. HW: p. 312 #45-46

Chemical Formulas:Empirical formula: the lowest whole-

number ratio of the atoms of elements in a compound

Molecular formula: the exact number of atoms of elements in a compound

For example, styrene (C2H2), and acetylene (C8H8) have different molecular formulas but the same empirical formula (CH)

Finding Empirical Formulas:Determining the MOLE RATIO of elements

in a compound.1. Find percent composition (if not given)2. Divide percent composition by molar

mass of element to get mole ratios3. Simplify to whole numbers by dividing all

mole ratios by the smallest one4. Write the formula with the subscripts

Empirical Formula: ExampleA compound contains 25.9% nitrogen, and 74.1%

oxygen. What is the empirical formula of this compound?

Empirical Formula: ExampleCalculate the empirical of these compounds:

1) 94.1% O, 5.9% H

2) 67.6% Hg, 10.8% S, 21.6% O

Molecular Formula: ExampleA compound has an empirical formula CH

and a molar mass of 104.2 g/mol. What is its molecular formula?

1. Divide the molar mass of the empirical formula by molar mass of the molecular formula.

2. Multiply all subscripts by that value.

Molecular Formula: ExampleA compound has an empirical formula CH

and a molar mass of 104.2 g/mol. What is its molecular formula?

Empirical Formula: ExampleCalculate the empirical formula of these

compounds:3) 36.1% Ca, 63.9% Cl

2) 40.0% C, 6.7% H, 53.3% O