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Chemistry 1201 Section 4
Spring 1999
Professor Russo
Exam #10
Type of exam: Take-home. You can work with anyone on this exam, including me! You should know how to
do these problems, though. You will probably see similar problems again.
Due: Tuesday, April 27, after the help session (5:00 pm Choppin 100)
80 points. After this exam, you will have had 930 total points. If you have more than 700, you can even
stop taking exams (except the final, of course!). However, I advise you that the kinds of problems shown
here ARE ON THE FINAL EXAM!!!
Show your work neatly. We will not grade papers that just show an answer, nor can we assign partial
credit if we don't see the work. If you find these problems hard, try working some of the easier assigned
problems first.
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Question #1. (BLB 3.103) HCN is a poisonous gas. The lethal dose is approximately 300 mg
HCN per kilogram of air when inhaled. Calculate the amount of HCN that gives the lethal
dose in a small laboratory room measuring 12 x 15 x 8 ft. The density of air at 26oC is
0.00118 g/cm3.
Worth 5 points
_________________________
grams of HCN to be lethal
Question #1. (BLB 3.103 continued) If the HCN is formed by reaction of NaCN with
H2SO4, what mass of NaCN gives the lethal dose in the room? See your book for the balanced
reaction, or figure it out: it is a standard acid-base reaction to produce salt & water.
Worth 5 points
_________________________
grams of NaCN required to kill
Chem 1201 Sec. 4
Exam #10
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Question #3. (BLB 10.26) The Hindenburg was a famous gas-filled dirigible, the pride of
National Socialism until it, like our Challenger space shuttle, exploded. Nazi Germany lacked
Helium in great quantities, so the Hindenburg instead flew inflated with highly explosive
hydrogen gas, H2. It was supposed to pick up safe, unreactive Helium in the USA on its illfated trip. Since H2 is lighter than air, it provides considerable lift, so that a giant baloon can
float effortlessly…unless the hydrogen should somehow explode. Suppose the Hindenburg
held 2.0 x 105 m3 of H2 at 27oC and 1.0 atm. What is the mass of hydrogen in grams? What
mass of water was produced when the H2 exploded? Relax…it's a simple stoichiometry
problem with a twist of ideal gas thrown in at the beginning.
Worth 5 points
_________________________
mass of H2 in grams
_________________________
mass of H2O in grams
Question #4. (based BLB 10.41) Ammonium sulfate, an important fertilizer, can be prepared
by the reaction of ammonia with sulfuric acid. The unbalanced reaction is:
NH3(g) + H2SO4(aq)  (NH4)2SO4(aq)
At 28oC and 33.0 atm, what volume of NH3(g) is needed to react with 825 kg of H2SO4?
Worth 5 points
Chem 1201 Sec. 4
Exam #10
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volume of ammonia
Question #5. (based on BLB 10.42) Glucose, C6H12O6, "burns" in our bodies using oxygen
to produce CO2 and H2O. Balance the reaction and calculate the volume of CO2 produced at
body temperature of 98.6oF and pressure of 1.00 atm when 5.00 glucose is metabolized. You
can assume all water vapor is removed from the CO2 prior to measurement (i.e., we want the
"dry volume" of CO2).
Worth 10 points
___________________________
volume of CO2
Chem 1201 Sec. 4
Exam #10
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Question #6. (similar to BLB 10.92 or 10.91) This problem uses what we know about
determining molecular formulae given percent composition. However, in this case we are not
given the molar mass. Instead, we use the ideal gas law to determine it. Here goes. A
particular gas is composed of 85.7 % C and 14.3 % H by mass. If 3.52 g of the gas has a
volume of 2.00 liter at 748 torr and 50.0oC, what is the molecular formula of the gas?
Worth 10 points
____________
molecular formula for the gas
Chem 1201 Sec. 4
Exam #10
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Question 7. (like BLB 4.8b) Compute the molarity of a solution that contains 0.0843 g
Na2SO4 in enough water to form 750.0 mL of total solution. Express your answer in three
separate ways: molarity of Na2SO4, molarity of Na+, and molarity of SO42-.
Worth 5 points
_______________
Molarity of Na2SO4
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Molarity of Na+
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Molarity of SO42-
Question 8. (based on BLB 4.8) How many grams of solute are present in 35.0 mL of 2.33
M Co(NO3)2? How many grams of Co? How many grams of N?
Worth 5 points
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g of Co(NO3)2
Chem 1201 Sec. 4
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g of Co
Exam #10
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g of N
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Problem 9 (BLB 4.52) How many mL of 0.155 M HCl are needed to neutralize completely
35.0 mL of 0.101 M Ba(OH)2? Begin by writing and balancing the reaction between HCl and
Ba(OH)2 to form a salt plus water. You can solve the problem either by "lining it out" or by
the famous titration equation: NaVa = NbVb where N is the "normality", equal to some integer
multiple of the molarity. The subscripts A and B stand for "Acid" and "Base". For example,
Normality = 2(Molarity) for Ba(OH)2 because it contains two hydroxide groups, while
Normality = Molarity for HCl.
Worth 10 points
______________________
mL of 0.155 M HCl required
Chem 1201 Sec. 4
Exam #10
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Problem 10 (BLB 13.22) A sulfuric acid solution containing 571.6 g of H2SO4 per liter of
solution has a density of 1.329 g/cm3. Calculate the mass percentage, mole fraction, molality
and molarity of H2SO4 in this solution.
Worth 10 points
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mass % H2SO4
Chem 1201 Sec. 4
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mole fraction, XH2SO4
Exam #10
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Molality, mH2SO4
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Molarity, MH2SO4
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Problem 11 (Based on BLB 13.56) Assuming full dissociation of the following compounds,
which has the lower freezing point?
a) 1.0 molal solution of H2SO4
b) 2.0 molal solution of HCl
c) 1.5 molal solution of NaNO3
d) 1.25 molal solution of Ca(NO3)2
e) 0.75 molal solution of FeCl3
Worth 5 points
Circle the correct answer, but you must JUSTIFY YOUR REASONING IN THE BOX
PROVIDED!
Problem 12 (Based on BLB 13.52) Lauryl alcohol is used in making soap. A solution of 5.00
g of lauryl alcohol in 0.100 kg of benzene freezes at 4.1oC. What is the molecular weight of
lauryl alcohol?
Worth 5 points
Chem 1201 Sec. 4
Exam #10
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