Percent Composition

What is Percentage Composition? 

The percent composition (percentage composition) of a compound is a relative measure of the mass of each different element present in the compound. 

How to Solve for Percentage Composition? 

To calculate the percentage composition of a compound:
1) Calculate the molecular mass of the compound
2) Calculate the total mass of each element present in the formula of the compound
3) Calculate the percentage composition: 

    % by weight (mass) of element = (total mass of element present ÷ molecular mass) x 100 

Example One: 

Find the percentage composition of a compound that contains 17.6 g of iron and 10.3 g of sulphur. The total mass of the compound is 27.9 g 

         Iron: (17.6 g/ 27.9 g) = 63.1%

         Sulfur: (10.3 g/ 27.9 g) = 36.9% 

         Fe = 63.1 %

           S = 36.1 %

                100.0% 

Example Two: 

Find the percentage composition of a compound that contains 30.2 g of bromine and 4.9 g of magnesium.  

         32.0g 

      +   4.9g

         36.9g (The total mass of the compound) 

         Bromine: (32.0 g/ 36.9 g) = 86.7%

         Magnesium: (4.9 g/ 36.9 g) = 13.3% 

         Br = 86.7 %

        Mg =13.3 %

                100.0% 

For a more insightful look into the world of percentage composition, feel free to watch the video below.

 

-Simon Sierra