Hoffman/Paustian 2010 Chem- Gas laws
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Hoffman/Paustian 2010 Chem- Gas laws
Overall Objective: Understand and apply the properties of gases
and the gas laws.
Iowa Model Core standards addressed:
o Understands and applies knowledge of the structure and properties of matter
o Designs and conducts scientific investigations
o Uses technology and mathematics to improve investigations and communications
o Apply critical literacy/thinking skills related to personal, family and community
wellness.
o Apply digital tools to gather, evaluate, and use information.
Key Concepts:
1. Explain why gases are easier to compress than solids or liquids are. (14.1.1)
2. Describe the three factors that affect gas pressure. (14.1.2)
3. Describe the relationships among the temperature, pressure, and volume of a gas.
(14.2.1)
4. Use the combined gas law to solve problems. (14.2.2)
5. Compute the value of an unknown using the ideal gas law. (14.3.1)
6. Compare and contrast real and ideal gases. (14.3.2)
7. Understand the effects of CO2 on the atmosphere and its impact on climate change.
Page 2 of 19
Hoffman/Paustian 2010 Chem- Gas laws
Atmospheric Pressure Practice
The values for standard atmospheric pressure in different units are as follows:
Units of Gas Presure
Units
Atmosphere
Inches of mercury
cm of mercury
mm of mercury
torr
pounds per square inch
kilopascal
Standard Pressure
1 atm (exactly)
29.9 in. Hg
76 cm Hg (exactly)
760 mm Hg (exactly)
760 torr (exactly
14.7 psi
101 kPa
If oxygen gas in a steel cylinder is at a pressure of 5.25 atm, what is the pressure in each of
the following units?
A) mm Hg
B) torr
C) cm Hg
D) inches Hg
If an automobile piston compresses a fuel-air mixture to a pressure of 7555 torr, what is the
pressure expressed in each of the following units?
A) psi
B) kPa
An American newscast states that the barometer reads 28.8 inches of Hg. Express the
atmospheric pressure in each of the following units:
A) atm
B) mm Hg
C) cm Hg
D) torr
Page 3 of 19
Hoffman/Paustian 2010 Chem- Gas laws
Ideal Gas Behavior
State the five characteristics of an ideal gas according to the kinetic theory.
At what Celsius temperature does a gas possess zero kinetic energy?
Temperature Conversions
Convert the following temperatures to the unit asked for:
1) 273K to oC
2) 0oC to oF
3) 0K to oC
4) 23oC to oF
5) The boiling points of five liquids are provided in either Celsius or Kelvin
temperatures. List the liquids in order from the one with the lowest boiling point
to the one with the highest boiling point.
Acetone (C3H6O)
329K
Heptane (C7H16)
98oC
Nitromethane (CH3NO2) 374K
Benzene (C6H6)
80oC
318K
Sulfur Trioxide (SO3)
Page 4 of 19
Hoffman/Paustian 2010 Chem- Gas laws
Boyle’s Law Practice
P1V1 = P2V2
Sketch a graph of pressure versus volume, assuming temperature is constant. Label the
vertical axis V, and the horizontal axis P.
A sample of air at 0.750atm is expanded from 250.0mL to 655.0mL. If the temperature
remains constant, what is the final pressure in atm?
What is the final volume of argon gas if 2.50L at 750 torr is compressed to a pressure of 150
torr? Assume the temperature remains constant.
A 1.50 L sample of methane gas exerts a pressure of 1650 mm Hg. Calculate the final
pressure if the volume changes to 7.00 L. Assume temperature remains constant.
A 50 mL sample of carbon monoxide gas at 25oC has a pressure of 15.0 psi. If the final
volume is 44.0 mL at 25oC, what is the final pressure in psi.
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Hoffman/Paustian 2010 Chem- Gas laws
Page 6 of 19
Hoffman/Paustian 2010 Chem- Gas laws
Charles’ Law Practice
V1/T1 = V2/T2
Sketch a graph of volume versus Kelvin temperature, assuming pressure is constant. Label
the vertical axis V, and the horizontal axis T(K).
A 335-mL sample of oxygen at 25oC is heated to 50oC. If the pressure remains constant,
what is the final volume in milliliters?
What is the final Celsius temperature if 4.50 L of nitric oxide gas at 35oC is cooled until the
volume reaches 1.00 L? Assume the pressure remains constant.
A 275 L helium balloon is heated from 20oC to 40oC. Calculate the final volume assuming the
pressure remains constant.
A krypton balloon has a volume of 555 mL at 21oC. If the balloon is cooled and the volume
decreases to 475 mL, what is the final temperature? Assume the pressure remains constant.
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Hoffman/Paustian 2010 Chem- Gas laws
Page 8 of 19
Hoffman/Paustian 2010 Chem- Gas laws
Gay-Lussac’s Law Practice
P1/T1 = P2/T2
Sketch a graph of pressure versus Kelvin temperature, assuming volume is constant. Label
the vertical axis P, and the horizontal axis T(K).
A sample of ammonia gas at 760 torr is heated from 20o to 200oC. If the volume remains
constant, what is the final pressure in torr?
A sample of xenon gas at 20oC and 0.570 atm is cooled to a pressure of 0.100 atm. If the
volume remains constant, what is the final Celsius temperature.
A 1.00-L sample of neon gas at 0oC has a pressure of 76.0 cm Hg. If the gas is heated to
100oC, what is the final pressure in cm Hg if the volume remains constant?
Page 9 of 19
Hoffman/Paustian 2010 Chem- Gas laws
Page 10 of 19
Hoffman/Paustian 2010 Chem- Gas laws
Combined Gas Law
P1V1 = P2V2
T1
T2
A 100.0-mL sample of hydrogen gas is collected at 772 mm Hg and 21oC. Calculate the
volume of hydrogen at STP.
A 5.00-L sample of nitrogen dioxide gas is collected at 5.00 atm and 500oC. What is the
volume of nitrogen dioxide under standard conditions?
If a sample of air occupies 2.00 L at STP, what is the volume at 75oC and 365 torr?
A sample of hydrogen fluoride gas has a volume of 1250 mL at STP. What is the pressure in
torr if the volume is 255 mL at 300oC?
A sample of air occupies 0.750 L at standard conditions. What is the pressure in atm if the
volume is 100.0 mL at 25oC?
A sample of krypton gas has a volume of 500.0 mL at 225 mm Hg and -125oC. Calculate the
pressure in mm Hg if the gas occupies 220.0 mL at 100oC.
Page 11 of 19
Hoffman/Paustian 2010 Chem- Gas laws
Page 12 of 19
Hoffman/Paustian 2010 Chem- Gas laws
Ideal Gas Law Practice
PV=nRT
R=0.0821 atm*L/mol*K
If 5.00 mol of hydrogen gas occupies 50.0 mL at 25oC, what is the pressure in atmospheres?
If 1.25 mol of oxygen gas exerts a pressure of 1200 mm Hg at 25oC, what is the volume in
liters?
If 10.0 L of nitrous oxide exerts a pressure of 125 psi at 373 K, what is the number of moles?
If 0.100 mol of argon gas occupies 2.15 L at 725 torr, what is the temperature in degrees
Celsius?
A sample of unknown gas weighs 1.95 g and occupies 3.00 L at 1.25 atm and 20oC. What is
the molar mass of the unknown gas?
A sample of chlorine gas occupies 1550 mL at 0.945 atm and 50oC. What is the mass of the
sample?
Page 13 of 19
Hoffman/Paustian 2010 Chem- Gas laws
Page 14 of 19
Hoffman/Paustian 2010 Chem- Gas laws
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