Name: ______________________________ Period: ______ Date: _____________
Empirical Formulas HW
1. Determine the simplest (empirical) formula for compounds that have the following analyses. The data
may not be exact.
a. 36.2% Al
63.8% S
b. 93.5% Nb
6.50% O
c. 66.0% Ba
34.0% Cl
d. 60.9% As
39.1% S
e. 76.89% Re
23.12% O
f. 57.6% Sr
13.8% P
28.6% O
g. 28.5% Fe
48.6% O
22.9% S
Empirical Formulas HW
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Name: ______________________________ Period: ______ Date: _____________
h. 80.38% Bi
18.46% O
1.16% H
i. 12.67% Al
19.73% N
67.60% O
j. 5.04% H
35.00% N
59.96% O
k. 24.3% Fe
33.9% Cr
41.8% O
l. 54.03% C
37.81% N
8.16% H
m. 55.81% C
3.90% H
29.43% F
10.85% N
n. 35.64% Zn
26.18% C
34.88% O
3.30% H
o. 8.09% C
0.34% H
10.78% O
80.78% Br
p. 2.8% H
9.8% N
20.5% Ni
44.5% O
22.4% S
2. Sometimes, instead of percentage composition, you will have the composition of a sample by mass.
Use the same method shown in Sample Problem 1, but use the actual mass of the sample instead of
assuming a 100 g sample. Determine the empirical formula for compounds that have the following
analyses:
a. a 0.858 g sample of a substance composed of 0.537 g of Cu and 0.321 g of F
b. a 13.07 g sample of a substance composed of 9.48 g of Ba, 1.66 g of C, and 1.93 g of N
Empirical Formulas HW
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Name: ______________________________ Period: ______ Date: _____________
c. a 0.025g sample of a substance composed of 0.0091 g Mn, 0.0106 g O, and 0.0053 g S
d. a 0.0082 g sample contains 0.0015 g of Ni and 0.0067 g of I
e. a 0.470 g sample contains 0.144 g of Mn, 0.074 g of N, and 0.252 g of O
f. a 3.880 g sample contains 0.691 g of Mg, 1.824 g of S, and 1.365 g of O
g. a 46.25 g sample contains 14.77 g of K, 9.06 g of O, and 22.42 g of Sn
h. a 0.400 g sample of a substance composed of 0.141 g of K, 0.115 g of S, and 0.144 g of O
i. a 10.64 g sample of a substance composed of 9.65 g of Pb and 0.99 g of O.
3. Determine the molecular formula of each of the following unknown substances:
a. CH2, experimental molar mass 28 g/mol
b. B2H5, experimental molar mass 54 g/mol
c. C2HCl, experimental molar mass 179 g/mol
d. C6H8O, experimental molar mass 290 g/mol
e. C3H2O, experimental molar mass 216 g/mol
Empirical Formulas HW
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Name: ______________________________ Period: ______ Date: _____________
f. C2H4S; experimental molar mass 179 g/mol
g. C2H4O; experimental molar mass 176 g/mol
h. C2H3O2; experimental molar mass 119 g/mol
i. C2H2O, experimental molar mass 254 g/mol
4. Find the empirical formula, then use the experimental molar mass to determine the molecular
formula for compounds having the following analyses:
a. 41.39% C, 3.47% H, and 55.14% O; experimental molar mass 116.07
b. 54.53% C, 9.15% H, and 36.32% O; experimental molar mass 88
c. 64.27% C, 7.19% H, and 28.54% O; experimental molar mass 168.19
d. A 2.65 g sample of a salmon-colored powder contains 0.70 g of Cr, 0.65 g of S, and 1.30 g of O.
The molar mass is 392.2. What is the formula of the compound?
e. A sample of histamine having a mass of 385 mg is composed of 208 mg of C, 31 mg of H, and
146 mg of N. The molar mass of histamine is 111 g/mol. What is the molecular formula for
histamine?
Empirical Formulas HW
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