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 35.41g Cr 38.03g 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 10.150 g sample of a compound containing only P and O yields 5.717 g of O. What is the simplest formula?

7. Example 3 What is the formula of a substance containing 63.52 g iron and 36.48 g of sulfur?

8. Percent Composition Percent of each element in a compound % = Mass of element x 100 Mass of compound

9. What of the % of Cu in Cu(NO 3 ) 2 ?