`Chemistry 400
Miller
Chapter 3 Homework Problems
1. A compound has the following elemental analysis:
Element
C
H
O
% composition
79.95
9.395
10.65
Its molar mass is around 300 g/mol. What is its molecular formula? Use online resources to determine the most likely common name
for this chemical.
2. A compound has the following elemental analysis:
Element
C
H
O
% composition
58.8
9.87
31.3
Its molar mass is around 100 g/mol. What is its molecular formula? Use online resources to determine the most likely common name
for this chemical.
3. A compound has the following elemental analysis:
Element
C
H
O
% composition
40.00
6.72
53.28
Its molar mass is around 180 g/mol. What is its molecular formula? Use online resources to determine the most likely common name
for this chemical.
4. A 2.448g kidney stone was analyzed and found to contain 0.766 g Ca, 1.223 g O, and 0.459 g C. What is the empirical formula of
the compound? Use online resources to determine the most likely common name for this chemical. Please show your calculations for
full credit.
5. An ionic compound was analyzed and found to contain 13.5 g Ca, 10.8 g O, and 0.675 g H. What is the empirical formula of the
compound? What is the name of the compound?
6. An ionic solid of iron, oxygen and hydrogen was analyzed and found to contain 1.55 g Fe, 0.890 g O, and 0.0561 g H. What is the
empirical formula of the compound and its name?
7. An ionic solid of iron, oxygen and hydrogen was analyzed and found to contain 1.31 g Fe, 1.12 g O, and 0.0707 g H. What is the
empirical formula of the compound and its name?
8. A sample of a blue crystal was found at an industrial laundry facility outside of Albuquerque, NM. The only four elements possibly
in the compound were determined to be C, H, N and O. Complete combustion of a 0.775 g sample of the unknown crystal with excess
O2 produced 2.286 g of CO2, 0.702 g of H2O and 0.0728 g N2. The molar mass of the substance was found to be about 150 g/mol.
What is the molecular formula of the unknown crystal? Use online resources to determine the most likely common name for this
chemical. Please show your work for this problem to receive credit.
9. A sample of a powder was found at a crime scene. It is believed that the powder is cocaine. The only four elements in the
compound were determined to be C, H, N and O. Complete combustion of a 0.563 g sample of the unknown powder with excess O2
produced 1.18 g of CO2, 0.310 g of H2O and 0.176 g NO2. The molar mass of the substance was found to be about 300 g/mol. What is
the molecular formula of the unknown powder? Was the substance cocaine? If not, then look on the internet to determine what you
think the substance was.
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10. A sample of a powder was found at a crime scene. It is believed that the powder is cocaine. The only four elements in the
compound were determined to be C, H, N and O. Complete combustion of a 3.54 g sample of the unknown powder with excess O2
produced 8.49 g of CO2 and 2.14 g of H2O. A separate analysis of 2.35 g of the unknown powder produced 0.199 g of N. The molar
mass of the substance was found to be 165 g/mol. What is the molecular formula of the unknown powder? Was the substance cocaine?
If not, then look on the internet to determine what you think the substance was.
11. A sample of a powder was found at a crime scene. It is believed that the powder is cocaine. The only four elements in the
compound were determined to be C, H, N and O. Complete combustion of a 0.150 g sample of the unknown powder with excess O2
produced 0.377 g of CO2, 0.0900 g of H2O and 0.0219 g NO2. The molar mass of the substance was found to be about 300 g/mol.
What is the molecular formula of the unknown powder? Was the substance cocaine? If not, then look on the internet to determine
what you think the substance was.
12. The mineral dwornikite contains a hydrate of nickel (II) sulfate with an unknown number of waters of hydration, NiSO4•xH2O
where x is unknown. If a 0.250 g sample of dwornikite is heated to constant weight over a Bunsen burner, its mass decreases to 0.224
g. What is the value of x for this hydrate? Support your answer with calculations to receive full credit.
13. A hydrate of nickel(II) sulfate has the following formula: NiSO4•xH2O. The water in a 3.41 g sample of the hydrate was driven off
by heating. The remaining sample had a mass of 2.01 g. Find the number of waters of hydration (x) in the hydrate.
14. A hydrate of copper(II) chloride has the following formula: CuCl2•xH2O. The water in a 3.41 g sample of the hydrate was driven
off by heating. The remaining sample had a mass of 2.04 g. Find the number of waters of hydration (x) in the hydrate.
15. A hydrate of copper(II) chloride has the following formula: CuCl2•xH2O. The water in a 2.78 g sample of the hydrate was driven
off by heating. The remaining sample had a mass of 1.98 g. Find the number of waters of hydration (x) in the hydrate.
16. An unknown powder has been found at a crime scene. It is your job to identify the chemical formula for the substance and its
common or generic name. Preliminary tests reveal that the possible elements that can be in the material are carbon, hydrogen,
oxygen and nitrogen.
A combustion analysis using the apparatus schematically pictured below has the following results:
Sample Size, g g CO2 g H2O 1.212 2.593 0.869 A separate analysis to determine the amount of nitrogen in the compound as ammonia found:
Sample Size, g g NH3 0.444 0.0668 Finally, the molar mass of the compound was found to be:
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226 g 17. An organic compound was synthesized & a sample of it was analyzed & found to contain only C, H, N, O, & Cl. It was observed
that when a 0.150 g sample of the compound was burned, it produced 0.138 g CO2 & 0.0556 g H2O. All the nitrogen in a different
0.200 g sample of the compound was converted to NH3, which was found to weigh 0.0238 g. Finally, the chlorine in a 0.125 g sample
of the compound was converted to Cl- and by reacting it with AgNO3, all of the chlorine was recovered as the solid AgCl. The AgCl,
when dried was found to weigh 0.251 g. What is the empirical formula of this compound?
18. A good rule of thumb is that there are 20 drops in a mL. How many water molecules are there in one drop of water? Assume that
the density of water is 1.0 g/mL.
19. The elements X and Y form a compound that is 40% X by mass and 60% Y by mass. The atomic mass of X is twice that of Y.
What is the empirical formula of the compound?
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