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Percent Composition


    To find the percent composition of molar mass, simply take the total of each element. Example: take 117.3 g of Potassium, divide it by the overall total of molar mass (212.27 g), and then multiply it by 100. This is your percent composition of molar mass for whichever element you are solving for.

K  --->  3  •  39.00 = 117.30
P  --->  1  •  30.97 = 30.97             IN TOTAL  =  212.27 g.
O  --->  4  •  16.00 = 64.00

K  --->  117.30  ÷  212.27  •  100  =  55.26%
P  --->  30.97  ÷  212.27  •  100  =  14.59%
O  --->  64.00  ÷  212.27  •  100  =  30.15%

    Ensure that all percent totals for each element equal a combined number of 100, or a number close to 100.

Remember to round two places after the decimal, unless otherwise noted.