Name ____________________________________________ Date _________________________ Period
HOMEWORK and TEST GRADE RECOVER
for Chapter 7: Chemical Quantities
7.5 Molecular Formulas (Read pgs. 210 - 213 in the chemistry textbook)
1. What is the difference between the molar mass of the molecular formula and the molar mass of the empirical
formula?
2. List the steps for calculating a Molecular Formula from an Empirical Formula.
3. The insecticide lindane has a percent composition of 24.78 % C, 2.08 % H, and 73.14 % Cl. If its molar
mass is about 291 g/ mol, what is the molecular formula? Follow ALL math work rules!
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4. Write the empirical formula of each of the following substances:
(a) C6H6O3, pyrolallol, a developer in photography
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(b) C6H12O6, galactose, a carbohydrate
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(c) C8H6O4, terephthalic acid, used in the manufacture of plastic bottles
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(d) C6Cl16, hexachlorobenzene, a fungicide
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(e) C24H16O12, laccaic acid, a crimson dye
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5. Caffeine has an empirical formula of C4H5N2O. If it has a molar mass of about 194 g, what is the molecular
formula of caffeine? Follow ALL math work rules!
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6. Glyoxyl, used in textiles; maleic acid, used to retard oxidation of fats and oils; and acontic acid, a platicizer,
all have the same empirical formula, CHO. What are the molecular formulas of each if: Follow ALL math
work rules!
(a) glyoxyl molar mass ≈ 58 g/ mol
(b) maleic acid molar mass ≈ 117 g/ mol
(c) acontic acid molar mass ≈ 174 g/ mol
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7. Chloral hydrate, a sedative, contains 14.523 % C, 1.828 % H, 64.303 % Cl, and 19.346 % O. If it has a of
about 165 g, what is the molecular formula of chloral hydrate? Follow ALL math work rules!
8. Lactic acid, the substance that builds up in muscles during exercise, has a molar mass of about 90 g and a
composition of 40.0 % C, 6.71 % H, and the rest is oxygen. What is the molecular formula of lactic acid?
Follow ALL math work rules!
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9. Adenine is a nitrogen-containing compound found in DNA and RNA. If adenine has a composition of
44.5 % C, 3.70 % H, and 51.8 % N, and a molar mass of about 135 g, what is the molecular formula of
adenine? Follow ALL math work rules!
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