Question
Madeline Christine Lowry – CHEM 107 – Dr. Bro
Problem Set #3
1
/res/tamu/lsbrown/Set3/Set3.page
Set 3 header
Problem Set #3 is due Tuesday night, October 1, at
11:59 PM.
5. A gas-filled weather balloon with a volume of 40.1 L is released at sea-level, where the prevailing conditions are 753.0
torr and 21.9◦ C. The balloon can expand to a maximum volume of 900 L. If the balloon rises to an altitude at which the
temperature is -9.2◦ C and the pressure is 0.069 atm, what
will the volume of the balloon be?
Here is a link to some additional hints for these problems.
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Problem 1
Due date: Tue Oct 1 11:59:59 pm 2013 (CDT)
1. What pressure is needed to confine an ideal gas to 195.0
L after it has expanded from 15.0 L and 2.3 atm at constant
temperature?
Problem 6
6.Use the drop down choices to mark each as either true or
false. You must get all five correct at the same time.
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You are correct. Your receipt no. is 160-7559
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Problems 2 & 3
2. A 280.0 L sample of gas of the upper atmosphere at a
pressure of 14.2 torr is compressed into a 215.0 mL container
at the same temperature. What is the new pressure?
You are correct. Your receipt no. is 160-4309
3. To what volume would the original sample have had to be
compressed to reach a pressure of 14.0 atm?
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Choices: True, False.
If a sample of gas is heated from 100◦ C to 200◦ C ,
volume will double.
If a sample of gas is heated from 473◦ C to 1219◦ C,
volume will increase by a factor of two.
If a sample of gas is heated from 0◦ C to 273◦ C,
volume will double.
If a sample of gas is cooled from 1000◦ C to 200◦ C,
volume will decrease by a factor of five.
If a sample of gas is cooled from 1273◦ C to 500◦ C,
volume will be halved.
the
the
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the
the
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Problem 7
7. At a height of 309 km above the Earth’s surface, an astronaut finds that the atmospheric pressure is about 1.20E-8
mmHg and the temperature is 551 K. How many molecules
of gas are there per milliliter at this altitude? (Enter the
number of molecules, with no units.)
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Incorrect.
Problem 4
4. A sample of sulfur hexafluoride gas occupies a volume of
5.37 L at 113.2◦ C. Assuming the pressure is constant, what
temperature (in ◦ C) is needed to reduce the volume to 2.48
L? (Use an uppercase C for the unit here, with no degree
sign.)
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Problem 8
8. Two gases, helium (18.4 grams) and ammonia (6.8 grams),
are confined in a container at a pressure of 1040.0 torr. Calculate the partial pressure of ammonia in torr. (You may
need to look up the formula for one or both of your gases.)
Incorrect.
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Problem 5
Problem 9
Madeline Christine Lowry – CHEM 107 – Dr. Bro
Problem Set #3
3
9. Liquid helium at 4.2 K has a density of 0.147 g/mL. Suppose that a 1.50-L metal bottle that contains air at 101K and
2.5 atm pressure is sealed off. If we inject 100.0 mL of liquid
helium and allow the entire system to warm to room temperature (25◦ C), what is the pressure inside the bottle?
13. Analysis of a volatile liquid shows that it contains 24.79
percent carbon, 2.04 percent hydrogen, and 73.17 percent
chlorine by mass. At 104.0◦ C and 4.2 atm, 477.0 mL of the
vapor has a mass of 6.270 g. What is the molar mass of the
compound?
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Problem 10
10. A mouse is placed in a sealed chamber with air at 751.0
torr. This chamber is equipped with enough solid KOH to
absorb any CO2 and H2O produced by the mouse. The gas
volume in this chamber is measured to be exactly 1.90 L, and
the temperature is held constant at 309K. After two hours
the pressure inside the chamber falls to 729.8 torr. What
mass of oxygen has the mouse consumed?
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Problem 11
11. Consider the following statements related to the kinetic
theory of gases. Use the drop down choices to mark each as
either true or false. You must get all five correct at the same
time.
Choices: True, False.
• The average speed of helium atoms at room temperature is less than the average speed of argon atoms at
room temperature.
• Gases behave most ideally at high temperatures.
• Temperature is a measure of the average kinetic energy
of the molecules in a gas.
• At a given temperature, all gases have the same average
kinetic energy.
• Gases behave most ideally at low pressures.
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Problem 12
12. An analysis is performed on an organic liquid with a
fishy odor. Vaporization of 240.0 mg of the compound in a
110-mL bulb at 170◦ C gives a pressure of 405.0 torr. What
is the molar mass of this compound?
14. For the compound above, determine the molecular formula. Enter your formula as plain text, with carbon first,
then hydrogen, the chlorine. So if the formula were C10H21Cl,
you would enter C10H21Cl.
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Problem 15
15. “Air” bags for automobiles are inflated during a collision
by the explosion of sodium azide, NaN3. The equation for
the decomposition is
2NaN3(s) → 2Na(s) + 3N2(g). What mass of sodium azide
would be needed to inflate a 15.7-L bag to a pressure of 1.6
atm at 25◦ C?
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Problem 16
16. Calculate the volume of nitrogen dioxide produced at
730.2 torr and 28.4◦ C by the reaction of 6.45 cm3 copper
(density = 8.95 g/cm3) with 200.1 mL of concentrated nitric
acid if the acid has a density of 1.42 g/cm3 and contains 68.0%
HNO3 by mass).
Cu(s) + 4HNO3(aq) → Cu(NO3)2(aq) + 2NO2(g) + 2H2O(l)
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Problem 17
17. A mixture of helium and neon gases has a density of
0.5632 g/L at 25◦ C and 790 torr. What is the mole fraction
of neon in this mixture?
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Problems 13 & 14
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