1. Empirical Formulas

2. Definition
Emperical formula – uses symbols form elements combined with subscripts showing the smallest whole number ratio of elements in a compound
Also called simplest formula

3. Example
A sample of a compound is determined to contain 26.56% of Potassium, 35.41% of chromium, and 38.03% oxygen. What is the simplest formula?
Step 1: Find the composition by mass of each element
26.56 g K g Cr g O

4. Step 2: Determine the composition in moles of each element

5. Step 3: Find the ratio of moles of elements by dividing through by the smallest number of moles

6. Example 2
Analysis of a g sample of a compound containing only P and O yields g of O. What is the simplest formula?

7. Example 3
What is the formula of a substance containing g iron and g of sulfur?