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Skills Worksheet
Concept Review
Section: Formulas and Percentage Composition
Solve the following problems, and write your answer in the space provided.
1. The mineral greenockite is a yellow sulfide of cadmium that is 78.0% cadmium
and 22.0% sulfur. Determine the empirical formula of greenockite.
2. What is the empirical formula for a compound of aluminum and fluorine that
is 32% aluminum and 68% fluorine?
3. What is the empirical formula for a compound that is 26.56% potassium,
35.41% chromium, and 38.03% oxygen?
4. What is the empirical formula for a compound that is 33.36% calcium, 26.69%
sulfur, and 40.00% oxygen?
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Holt Chemistry
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The Mole and Chemical Composition
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Concept Review continued
5. What is the empirical formula for a compound that is 29.44% calcium, 23.55%
sulfur, and 47.01% oxygen? This compound is a common ingredient in plaster.
6. The empirical formula of a compound is CH. The experimental molar mass is
78.12 g/mol. Determine the molecular formula of the compound.
7. The empirical formula of a compound is CH2O. The experimental molar mass
is 60.06 g/mol. Determine the molecular formula of the compound.
8. The empirical formula of a substance is P2O5. The experimental molar mass is
283.89 g/mol. Determine the molecular formula of the compound.
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Holt Chemistry
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The Mole and Chemical Composition
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Concept Review continued
9. The empirical formula of a substance is BH3. The experimental molar mass is
27.67 g/mol. Determine the molecular formula of the compound.
10. The empirical formula of a compound is CH. The experimental molar mass is
26.04 g/mol. Determine the molecular formula of the compound.
11. Quartz has the chemical formula SiO2. What is the percentage composition of
this compound?
12. Urea, a component in fertilizer, has the chemical formula, CO(NH2)2. What is
the percentage composition of this compound?
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The Mole and Chemical Composition
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Concept Review continued
13. Fructose, a sweetener in soft drinks, has the chemical formula C6H12O6. What
is the percentage composition of this compound?
14. Which of two common ingredients in garden fertilizers, ammonium sulfate,
(NH4)2SO4, or ammonium phosphate, (NH4)3PO4, has a greater percentage of
nitrogen?
15. Which compound has the greater percentage of zinc—smithsonite, ZnCO3, or
sphalerite, ZnS?
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Holt Chemistry
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The Mole and Chemical Composition
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TEACHER RESOURCE PAGE
Answer Key
Concept Review:
Avogadro’s Number and
Molar Conversions
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
FOUR STEPS FOR SOLVING
QUANTITATIVE PROBLEMS
1.
2.
3.
4.
5.
6.
2.41 1024 atoms Al
9.33 1023 atoms Na
44.0 mol F
70.7 mol H2
291 mol K
877 g Sb
119 g U
167 g Fr
0.7239 mol Pb
2.54 x 105 mol Au
Concept Review: Relative
Atomic Mass and Chemical
Formulas
1.
2.
3.
4.
5.
6.
7.
8.
Additional Problems
85.47 amu
35.45 amu
310.18 g/mol
79.88 g/mol
84.01 g/mol
94.12 g/mol
26.04 g/mol
18.02 g/mol
7.
8.
9.
10.
11.
12.
13.
14.
15.
0.026 mm
3.21 L
0.80 g/cm3
21.4 g/cm3
30 boxes
a. 1.73 L
0.120 m 0.120 m 0.120 m
b. 9.2 g; 5.0 cm3
c. 60.4 kg; 1.88 104 dm3
d. 0.94 g/cm3; 5.3 104 m3
e. 2.5 103 kg; 2.7 106 cm3
2.8 g/cm3
a. 0.72 m
b. 2.5 103 atoms
1300 L/min
1.3 106 cal/h
5.44 g/ cm3
2.24 104 cm3
32 000 uses
2500 L
9.5 L/min
MOLE CONCEPT
1. a.
b.
c.
d.
e.
f.
2. a.
b.
c.
d.
e.
f.
3. a.
b.
c.
d.
e.
f.
Concept Review: Formulas
and Percentage Composition
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
CdS
AlF3
K2Cr2O7
CaSO3
CaSO4
C6H6
C2H4O2
P4O10
B2H6
C2H2
Si 46.75%, O 53.25%
19.99% C, 26.64% O, 46.65% N, 6.73% H
39.99% C, 6.73% H, 53.28%
(NH4)3PO4 has the greater percentage
of nitrogen.
15. Sphalerite, ZnS, has the greater percentage of zinc.
3.7 104 mol Pd
150 mol Fe
0.040 mol Ta
5.38 105 mol Sb
41.1 mol Ba
3.51 108 mol Mo
52.10 g Cr
1.5 104 g or 15 kg Al
8.23 107 g Ne
3 102 g or 0.3 kg Ti
1.1 g Xe
2.28 105 g or 228 kg Li
1.02 1025 atoms Ge
3.700 1023 atoms Cu
1.82 1024 atoms Sn
1.2 1030 atoms C
1.1 1021 atoms Zr
1.943 1014 atoms K
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Holt Chemistry
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The Mole and Chemical Composition