Percent Composition is the how much an element is to that of the compound it’s in. When given a compound, let’s say we want to know the percentage of Potassium in K2C2O7, which would be Potassium Dicarbonate. You would take the weight of the element from the Periodic Table and add them together. Potassium weights 39.09 amu, Carbon weights 12.01 amu, Oxygen weighs 16.00 amu. Now just add them up to get the sum of the compound. 2(39.0 amu)+2(12.01amu)+7(16.00amu)= 214.18 amu. Now divide the total amount of weight by the weight of Potassium (in the compound). 78.18/214.18= .365 or %36.5. Using percent composition in Chemistry can help us with the amount of a component in a compound.