CHM 1310 FS04 EXAM 4 0800 T/TH
Name: __________________________
Ganley
Date: _____________
Word Problem (20 points):
n-caproic acid is a monoprotic acid containing only carbon, hydrogen, and oxygen. It is
found in milk fats, coconut oil, and various palm and other oils. In spite of it's
characteristic goat-like odor, it is used in the food industry for the manufacture of
chemicals for artificial flavors. Caproic acid's composition by mass is:
C 62.04%, H 10.41%, O 27.55%
If a 10.00 g sample of caproic acid is dissolved in 1 L of water, 49.34 mL of 1.745 M
sodium hydroxide is required to titrate the solution. What is the molecular formula for
caprioc acid? You must show all work to receive any credit.
Page 1
1. The SO2 present in air is mainly responsible for the acid rain phenomenon. Its
concentration can be determined by titrating against a standard permanganate solution
as follows:
5SO2 + 2MnO4- + 2H2O  5SO42- + 2Mn2+ + 4H+
Calculate the number of grams of SO2 in a sample of air if 7.37 mL of 0.00800 M
KMnO4 solution are required for the titration.
A) 9.43  10–3 g
B) 5.89  10–5 g
C) 7.37  10–3 g
D) 2.24  10–4 g
2. A pressure that will support a column of Hg to a height of 256 mm would support a
column of water to what height? The density of mercury is 13.6 g/cm3; the density of
water is 1.00 g/cm3.
A) 348 cm
B) 1.00  102 ft
C) 18.8 mm
D) 33.8 ft
E) 76.0 cm
3. Why do astronauts have to wear protective suits when they are on the surface of the
moon?
A) The atmospheric pressure on the moon is too high, it would crush them.
B) The atmospheric pressure on the moon is too low, their cells would all rupture and
release gasses, killing them.
C) The temperatures are too cold, or too hot, to sustain life for long; and there is no
oxygen to breathe.
D) both b and c
4. Calculate the volume in mL of a 1.420 M NaOH solution required to titrate 25.00 mL of
a 4.500 M H2SO4 solution.
A) 56.25 mL
B) 158.5 mL
C) 112.5 mL
D) 225.0 mL
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5. A sample of gas has a volume of 47.0 L at 70.8C. The gas is heated to 83.8C at
constant pressure. What is the final volume of this gas?
A) 48.8 L
B) 45.3 L
C) 55.6 L
D) 2.21e–2 L
E) 2.52e–2 L
6. A sample of air occupies 3.8 L when the pressure is 1.2 atm. What pressure is required
in order to compress it to 0.075 L? (The temperature is kept constant.)
A) 42 atm
B) 0.24 atm
C) 24 atm
D) 61 atm
7. A sample of gas occupies 1.00e3 mL at 25C and 680 mmHg. What volume will it
occupy at the same temperature and 810 mmHg?
A) 5.5e8 mL
B) 1.2e3 mL
C) 5.5e2 mL
D) 8.4e2 mL
E) 1.2e–3 mL
8. A 50.0 mL sample of 0.436 M NH4NO3 is diluted with water to a total volume of 250.0
mL. What is the ammonium nitrate concentration in the resulting solution?
A) 21.8 M
B) 0.459 M
C) 2.18  102 M
D) 8.72  102 M
E) 0.109 M
9. The concentration of a hydrogen peroxide solution can be conveniently determined by
titration against a standardized potassium permanganate solution in an acidic medium
according to the following equation:
2MnO4– + 5H2O2 + 6H+  5O2 + 2Mn2+ + 8H2O
If 36.44 mL of a 0.01652 M KMnO4 solution are required to completely oxidize 25.00
mL of a H2O2 solution, calculate the molarity of the H2O2 solution.
A) 1.518 × 10–3 M
B) 6.023 × 10–4 M
C) 0.06020 M
D) 0.02012 M
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10. A 0.9182 g sample of CaBr2 is dissolved in enough water to give 500. mL of solution.
What is the calcium ion concentration in this solution?
A) 9.19  103 M
B) 2.30  103 M
C) 2.72  103 M
D) 4.59  103 M
E) 1.25  103 M
11. Which of the following is a correct half-reaction for the reaction: 2Sr + O2  2SrO
A) Sr  Sr+ + e–
B) Sr + 2e–  Sr2–
C) Sr  Sr2+ + 2e–
D) Sr + e–  Sr–
12. Calcium oxalate (CaC2O4) is insoluble in water. For this reason it can be used to
determine the amount of Ca2+ ions in fluids such as blood. The calcium oxalate isolated
from blood is dissolved in acid and titrated against a standardized KMnO4 solution by
the equation 2MnO4– + 16H+ + 5C2O42-  2Mn2+ + 10CO2 + 8H2O. In one test it is
found that the calcium oxalate isolated from a 10.0-mL sample of blood requires 24.2
mL of 9.56  10–4 M KMnO4 for titration. Calculate the number of milligrams of
calcium per milliliter of blood.
A) 0.231 mg/mL
B) 0.542 mg/mL
C) 2.96 mg/mL
D) 2.31 mg/mL
13. How many moles of MgCl2 are present in 60.0 mL of 0.100 M MgCl2 solution?
A) 60.0 moles
B) 0.572 moles
C) 6.00 × 10–3 moles
D) 6.00 moles
14. Oxygen (O2) and carbon dioxide (CO2) are colorless and odorless gases. What chemical
test would allow you to distinguish between these two gases?
A) Attempt to dissolve each gas in water; oxygen will dissolve, while carbon dioxide
will not
B) Attempt a combustion reaction, which will work in an atmosphere of oxygen, but
not carbon dioxide
C) Place gold in the presence of each; gold will oxidize in the presence of oxygen, but
not carbon dioxide
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15. A 3.664-g sample of a monoprotic acid was dissolved in water. It took 20.27 mL of a
0.1578 M NaOH solution to neutralize the acid. Calculate the molar mass of the acid.
A) 1145 g/mol
B) 3198 g/mol
C) 578.2 g/mol
D) 2121 g/mol
16. When excess AgNO3 is added to 50.0 mL of a solution of MgCl2, an AgCl precipitate
forms immediately. The precipitate is then filtered from the solution, dried, and
weighed. If the recovered AgCl is found to have a mass of 0.1183 g, what was the
concentration of magnesium ions in the original MgCl2 solution?
A) 0.300 M
B) 8.25  103 M
C) 1.65  102 M
D) 2.06  105 M
E) 4.13  103 M
17. Iodate ion, IO3-, oxidizes SO32- in acidic solution. The half-reaction for the oxidation is
SO32– + H2O  SO42– + 2H+ + 2e–
A 100.0-mL sample of solution containing 1.390 g of KIO3 reacts with 32.5 mL of
0.500 M Na2SO3. What is the final oxidation state of the iodine after the reaction has
occurred?
A) +7
B) +1
C) 0
D) –1
18. What volume of a 0.500 M HCl solution is needed to completely neutralize 10.0 mL of a
0.200 M Ba(OH)2 solution?
A) 10.0 mL
B) 0.200 mL
C) 2.00 mL
D) 8.00 mL
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19. A sample of a gas occupies 1.40  103 mL at 25ºC and 760 mmHg. What volume will it
occupy at the same temperature and 380 mmHg?
A) 2,800 mL
B) 2,100 mL
C) 1,400 mL
D) 1,050 mL
E) 700 mL
20. A sample of nitrogen gas has a volume of 32.4 L at 20ºC. The gas is heated to 220ºC at
constant pressure. What is the final volume of nitrogen?
A) 2.94 L
B) 19.3 L
C) 31.4 L
D) 54.5 L
E) 356 L
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Answer Key
Word problem:
Calculate the molecular mass of caproic acid:
1.745 mol NaOH 1L NaOH 1 mol caproic


 0.08609 mol caproic
1L NaOH
1000 mL 1 mol NaOH
Since the sample of caproic acid is 10.00 g:
49.34 mL NaOH 
molecular mass =
grams
10.00 g

 116.16 g/mol
mol
0.08609mol
If mw = 116.16 and the compound is 62.04% carbon, each molecule must have:
116.16g acid/mol acid×0.6204g C/g acid
=6 mol C/mol acid
12.01 g C/mol C
and:
116.16 g acid/mol acid  0.1041g H/g acid
 12 mol H/mol acid
1.008 g H/mol H
and:
116.16 g acid/mol acid  0.2755 g O/g acid
 2 mol O/mol acid
16.00 g O/mol O
and the molecular formula is C6H12O2
1.
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A
A
D
B
A
D
D
D
C
A
C
A
C
B
A
B
C
D
A
D
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