How to find the Percent Composition of a
Substance!
Example 1:
To find the percent composition of red M&M’s in a bag of 200 M&M’s,
if there are 26 red, you would use this formula.
Mass of Sample x 100 = Percent Composition
Total mass in the sample
So, in the M&M’s problem:
26 red x 100 = 13%
200 total
Example 2:
Find the percent composition of copper (Cu) in CuBr2.
Mass of Cu in the compound x 100 = Percent Composition
Total Mass of CuBr2 Compound
63.546 grams x 100 = 28.4%
223.354 grams
Percent Composition Practice
Find the percent compositions of all of the elements in the following compounds:
1) CuBr2
Cu: ___________
Br: ___________
2) NaOH
Na: ___________
