Chemistry

Percent Composition, Empirical and Molecular Formula



1. Turquiose has the following formula : CuAl 6(PO4)4(OH)8 .4H2O . Calculate the mass percent of each
element in turquoise.
Cu = 1 x 64 = 64 % Cu = 64/ 814 x 100 % = 7.9 %

Al = 6 x 27 = 162 % Al = 162/814 x 100 % = 19.9 %

P = 4 X 31 = 124 % P = 124 /814 x 100 % = 15.2%

O = 28 X 16 = 448 % O = 448/814 x 100 % = 55.0 %

H = 16 X 1 = 16 % H = 16/814 x 100 % = 2.0 %

814 100 %

2. Diazepam is the addictive tranquilizer also known as Valium. Its simplest formula is C 16H13N2OCl.
Calculate the mass percent of each element in this compound.


C = 16 X 12 = 192 % C = 192/284.5 X 100% = 67.5 %

H = 13 X 1 = 13 % H = 13/284.5 X 100% = 4 .6 %

N = 2 X 14 = 28 % N = 28/284.5 X 100% = 9.8 %

O = 1 X 16 = 16 % O = 16/284.5 X 100% = 5.6 %

Cl = 1 x 35.5 = 35.5 % Cl = 35.5/284.5 X 100% = 12.5 %

284.5 100%

3. A tablet of Tylenol has a mass of 0.611 g. It contains 251 mg of this active ingredient ,

acetaminophen C8H9NO2
a. What is the mass percent of acetaminophen in a tablet of Tylenol?
0.251 𝑔
x 100% = 41.1 %
0.611 𝑔




b. Assume that all the nitrogen in the tablet is in the acetaminophen . How many grams of nitrogen
are present in the tablet Tylenol?
C8H9NO2