To calculate the molecular mass of a compound, find its chemical formula. Using the chemical formula of the compound, determine the weight of each atom present and add up all of the atomic weights. The sum is the molecular mass of the compound under investigation.Continue Reading
First, look up the chemical formula for the compound under investigation. The chemical formula provides you information about which elements and how much of each element makes up the compound. For example, the chemical formula for water is H2O. This means that water is made of two hydrogen atoms and one oxygen atom.
Using the periodic table of elements, find the atomic weight of the elements that make up the compound. Multiply the atomic weight of each element by the number of atoms in the compound. For example, water is made up of two hydrogen atoms and one oxygen atom. The atomic weight of hydrogen is approximately 1, and the atomic weight of oxygen is about 16. After multiplying the number of atoms present in water, the value of hydrogen is 2 and the value of oxygen remains at 16.
Lastly, add the values element found in step two. The sum of these numbers gives you the molecular mass of the compound. Continuing with the example for water, 2 (hydrogen) + 16 (oxygen) = 18.