Empirical Formulas

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

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

Step 2: Determine the composition in moles of each element

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

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?

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