Unit 5: Gases and Atmospheric Chemistry
Chapter 11: The Gas State and Gas Laws
Section 11.1: States of Matter and the Kinetic Molecular Theory, pages 173–175
1. Answers may vary. Sample answer:
Figure 1
2. Solids are difficult to compress because of the attractive forces that keep molecules in solids close together.
In a solid, these forces prevent compression.
3. A skunk’s odour is essentially a gas that is being emitted from the skunk. Since gases take the shape of their
container (in this case the outdoors), the distances between gas molecules is great. This gas is spread over a
long distance, which is why you can smell it in your car for several miles.
4. (a) Brownian motion is the random movement of microscopic particles suspended in a liquid or gas.
(b) Kinetic molecular theory is the idea that all substances are comprised of molecules that are in constant
random motion.
5. b
6. Table 1 Properties of the Three Types of Motion
Type of Motion
Properties
translational motion
1. Movement through space along a straight line
2. Found in gases and liquids
rotational motion
1. The spinning of a molecule in place
2. Found in gases and liquids
vibrational motion
1. Back and forth vibration of molecules
2. Found in solids, liquids, and gases
7. False. Solids have vibrational motion only and the strongest strength of attraction between molecules.
8. When they are heated, the molecules in a gas move more rapidly and move farther apart.
9. (a) The substance is a solid. When a solid is heated its molecules vibrate faster but because of the strong
attractive forces the molecules of the solid do not move farther apart.
(b) The substance is a gas. Gases and liquids both experience an increase in vibrational, rotational, and
translational motion when they are heated. Gases can expand significantly, filling up the room.
10. c
11. As a substance is heated, its molecules move faster and become farther apart. When this occurs in a liquid,
the liquid may change into a gas. This is known as a change in state.
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Chapter 11: The Gas State and Gas Laws
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12. (a) The molecules in the solid begin to move faster and farther apart.
(b) As the ice warms, the kinetic energy in the molecules increases. This increase in kinetic energy allows the
molecules to overcome the attractive forces that keep the ice in its solid state. When this occurs, ice undergoes
a change of state and becomes a liquid.
Section 11.2: The Atmosphere and Its Components, pages 176–178
1. b
2. False. The mesosphere is less dense than the stratosphere.
3. The oxygen concentration is higher in the stratosphere. Air density and oxygen concentration decrease the
higher up you go in the atmosphere.
4. d
5. As altitude increases, the temperature of the stratosphere does not decrease because the stratosphere contains
ozone, which has the ability to capture ultraviolet radiation from the Sun. This trapped energy is released into
gas molecules, increasing the kinetic energy and temperature of the stratosphere.
6. Answers may vary. Sample answer:
Figure 1
7. Gas molecules in the thermosphere absorb solar radiation and become ionized. This ionization of gas
molecules results in the radiation of light. The light forms the auroras seen in the sky.
8. (a) This process is part of the nitrogen cycle.
(b) This process is important to sustaining human life on Earth because soluble nitrates are absorbed by plants
and used for food. Plants have a number of important uses for sustaining life. In addition to producing oxygen,
plants are used by humans for food. Nitrates are needed to grow the food we eat.
(c) When a plant decays, it releases nitrogen back into the atmosphere so that the nitrogen cycle can begin all
over again.
9. Ozone being depleted in the stratosphere is cause for alarm because ozone in the atmosphere absorbs
ultraviolet light from the Sun and provides a shield. This shield prevents excess UV light from reaching
Earth’s surface. Excess UV light can cause damage to DNA and increase the risk of cancer.
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Chapter 11: The Gas State and Gas Laws
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10. Carbon dioxide is extremely important to plants because it is used by them to produce glucose during
photosynthesis. Photosynthesis provides the plant with energy so that it can produce oxygen. Oxygen is vital to
human life.
11. Answers may vary. Sample answer: The atmosphere contains greenhouse gases that trap radiation from the
Sun. These gases vibrate at certain frequencies and send captured energy in all directions. Some of the energy
is sent back down to Earth’s surface where it warms the ground. Trapping radiation by greenhouse gases is
known as the greenhouse effect.
12. True
13. Answers may vary. Sample answer:
Table 1 Effects of Climate Change
Effect of climate change
Risk
sea levels rise
flooding in coastal areas
changes in mean temperature
could kill plant life
decrease in water level of the Great Lakes
loss of an important source of fresh water
14. Answers may vary. Sample answer:
Table 2 Common Types of Carbon Sequestration
Type of sequestration Example of a strategy
Major benefits or risks
biological
planting trees
• simple
• natural
geological
pumping liquid CO2 into
• expensive
depleted oil or gas reservoirs
• requires a lot of energy
• CO2 may leak back into the atmosphere or into
groundwater
• in groundwater, CO2 can combine with water to
form acids
Section 11.3: Chemistry Journal: The Road to Discovering Argon, page 179
1. Noble gases such as argon are inert substances. This means that they do not readily react with other
substances.
2 Answers may vary. Sample answer:.
(a) Helium and neon are examples of two other noble gases.
(b) Noble gases are important because they have little reactivity and can be used in numerous applications such
as lighting, lasers, and medicine. These elements can also be used as cryogenic refrigerants because of their
low boiling and melting points.
3. Before Rayleigh discovered argon, he did not know that argon was present in the air. He assumed air was
comprised of oxygen and nitrogen. As a result, Rayleigh also assumed that by removing the oxygen from air,
he would be left only with nitrogen.
4. Ramsey finally solved the mystery of the unknown gas in the atmosphere by using an approach similar to
that of Rayleigh’s. Ramsey assumed that air was comprised of oxygen, nitrogen, and a mystery gas. By
removing both the oxygen and the nitrogen from the air, Ramsey was able to isolate the mystery gas and
finally identify it.
5. The discovery of argon was a challenge to chemists because by the time Ramsey discovered argon, chemists
had developed a periodic table that had a formal structure. Argon was a unique element that did not “fit” into
the existing periodic table. In order to make it fit, Ramsey had to suggest that a new column be added. Many
chemists were not happy about this change.
6. Once argon was discovered and the periodic table was changed, scientists were able to explore the
possibility that there were other noble gases that could be included in the table. Within five years of the
discovery of argon, all of the remaining noble gases had been discovered.
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Chapter 11: The Gas State and Gas Laws
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Section 11.4: Air Quality, pages 180–181
1. Table 1 Photochemical Smog
definition
a complex mixture of air pollutants that is produced by human activity
composition
ground level ozone gases and particulate matter
where it comes from
results from a combination of vehicle and factory emissions with sunlight
appearance
often appears as a brown haze over a city
impact on human health eye and throat irritation, aggravates respiratory diseases such as asthma,
increases healthcare costs and contributes to absenteeism, contributes to
premature death
2. Particulate matter is a mixture of solid and liquid particles found in the atmosphere.
3. Answers may vary. Sample answers: Contributors to the release of particulate matter into the environment
include the burning of gasoline by car engines, coal-powered electric plants, the burning of trash, and heating a
home with coal.
4. Table 2 Sulfur Dioxide
balanced equation for the burning of sulfur in oxygen
S8 + 8 O2 → 8 SO2
physical properties
colourless gas, strong choking odour
impact on environment
contributes to the development of acid rain
5. The concentration of carbon monoxide is higher in urban areas because they typically have more cars,
traffic, and industrial operations—activities that release carbon dioxide. Since these activities are concentrated
in a specific area, this will increase the amount of carbon dioxide in the atmosphere.
6. Carbon monoxide is produced during incomplete combustion.
7. False. Volatile organic compounds (VOCs) include carbon-containing compounds that vaporize readily.
8. (a) Ground level ozone is produced from the reaction of nitrogen oxides and volatile organic compounds in
the presence of sunlight.
(b) The concentration of ground level ozone is highest on sunny days because it is formed when nitrogen
dioxide decomposes to release an oxygen atom that combines with an oxygen molecule to form ozone using
energy of the sunlight. When it is sunny, more of these reactions can occur. This will result in higher ozone
production.
(c) Cars use gasoline, which is a volatile organic compound. If more people use public transportation, this will
reduce the amount of VOCs in the air and reduce the amount of ground level ozone that will be produced.
9. Answers may vary. Sample answer: Since an AQHI of 8 represents high health risks, particularly to people
with cardiovascular or respiratory problems. I would probably not play that day, or I might ask my coach if I
could play shorter shifts or take longer rests between shifts.
Section 11.5: Indoor Air Quality, pages 182–183
1. (i) printers and copiers in home offices
(ii) combustion in fireplaces
(iii) lit candles and cigarettes
2. Off-gassing is the release of gases from a substance at room temperature.
3. False. Off-gassed chemicals are usually volatile organic compounds (VOCs) that evaporate into the air at
room temperature.
4. Paint smell dissipates over time because paint contains volatile organic compounds that off-gas. As time
passes, the level of VOCs decrease as they evaporate from the paint. When the VOCs are gone, the smell is
gone, too.
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Chapter 11: The Gas State and Gas Laws
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5. Answers may vary. Sample answer:
Table 1 Methanal
products from which
pressed wood, paints, coatings, cosmetics, wallpaper, cardboard,
methanal can be off-gassed fabrics, draperies
health risks
cancer; eye, nose, and throat irritation; allergic sensitivity;
respiratory problems
ways to minimize exposure • do not smoke inside or near your home
to methanal at home
• do not idle cars or gas-powered equipment near open windows or
doors
• ensure fireplaces and wood stoves are clean and in working order
• avoid bringing products with methanal into the home
• air out products containing methanal before bringing them into the
home
6. Figure 1
7. mild symptoms: shortness of breath, nausea, headaches
moderate symptoms: headaches, dizziness, nausea, light-headedness
severe symptoms: unconsciousness, death
8. 2 CH4(g) + 3 O2(g) → 2 CO(g) + 4 H2O(l)
9. Radon is the leading cause of lung cancer among non-smokers.
10. Indoor pollution includes biological agents such as skin cells. Since pets shed skin cells, they are a natural
source of biological pollution in the home.
11. Biological contaminants thrive in conditions of high humidity.
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Chapter 11: The Gas State and Gas Laws
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Section 11.6: Explore an Issue in Atmospheric Chemistry: Car Idling, page 184
1. Answers may vary. Sample answer: Toxic airborne chemicals that are produced from car exhaust include
carbon monoxide, nitrogen oxides, VOCs, and particulate matter.
2. Answers may vary. Sample answer:
Figure 1
3. The engine of an idling car produces a much larger amount of pollutants than a car running at 60 km/h
because it operates at a lower temperature. The combustion of fuel is not as efficient at a lower temperature,
resulting in incomplete combustion. Incomplete combustion produces more waste products. More complete
combustion of fuel occurs in a car travelling at 60 km/h, which results in the production of less waste.
4. Children are at a higher risk for developing health problems related to poor air quality because they breathe
more frequently than adults and consume more air. In doing so, children may inhale more pollutants than
adults.
Section 11.7: Atmospheric Pressure, pages 185–186
1. b
2. False. Pressure is directly related to the force applied.
3. If the same force is applied to a small area and a large area, the small area will have the largest pressure.
Force applied to a smaller area will be more concentrated, producing more pressure.
4. (a) Standard air pressure is about 101 kPa.
(b) Standard air pressure is also measured in atmospheres.
5. Standard temperature and pressure refers to conditions at 0 °C and 101.325 kPa. Standard ambient
temperature and pressure refers to conditions at 25 °C and 100 kPa.
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Chapter 11: The Gas State and Gas Laws
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6. Given: P = 0.875 atm
Required: pressure in mm Hg, P
Analysis: 1 atm = 760 mm Hg
Solution:
P = 0.875 atm !
760 mmHg
1 atm
P = 665 mmHg
Statement: 0.875 atm is equivalent to 665 mm Hg.
7. As the altitude increases, air density decreases. Air that is less dense has less oxygen. In the higher
elevations of Mt. Everest, climbers may not be able to acquire enough oxygen from the atmosphere and
therefore require oxygen tanks.
8. False. The density of atmospheric gases is greatest at sea level.
9. (a) The cylinder does not collapse because the gas inside the tank exerts a pressure on the inside of the tank,
balancing the pressure on the outside of the tank.
(b) Increased external air pressure on the tank would eventually cause it to collapse. When the outward
pressure exerted on the inside of the tank is less than the pressure outside of the tank, the tank would be
crushed.
(c) If the pressure inside the tank increased above that of the external atmospheric pressure, the tank would
explode.
10. In high altitude training, low levels of oxygen in the atmosphere at high altitudes force the body to produce
more red blood cells. When the athlete competes at a normal altitude, the body can absorb more oxygen from
the air, increasing the body’s ability to use oxygen.
Section 11.8: The Gas Laws—Absolute Temperature and Charles’ Law, pages
187–188
1. When the volume of a gas reaches zero, it approaches absolute zero or –273.15 degrees Celsius.
2. False. At absolute zero, there is no kinetic energy in the gas and therefore no thermal energy.
3. Given: t = 50 °C
Required: T
Analysis: T = t + 273
Solution:
T = t + 273
= 50 + 273
T = 323
Statement: A temperature of 50 °C is equivalent to 323 K.
4. (a) According to Charles’ Law, if absolute temperature is doubled, the volume of the gas will double.
(b) No, if the Celsius scale is used, the same result will not occur. Doubling temperature in Celsius will not
double the volume of a gas.
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Chapter 11: The Gas State and Gas Laws
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5. Answers may vary: Sample answer:
Figure 1
6. Answers may vary. Sample answer:
Figure 2
7. Given: t1 = 45 °C; t2 = 75 °C; V1 = 0.410 L
Required: volume of gas at 75 °C, V2
Analysis:
V1
T1
=
V2
T2
Solution:
Step 1: Convert temperature values to kelvins.
T = t + 273
T1 = t1 + 273
= 45 + 273
T1 = 318 K
T2 = t2 + 273
= 75 + 273
T2 = 348 K
Step 2: Rearrange the Charles’ law equation to isolate V2.
V2 =
V1T2
T1
Step 3: Substitute values into the equation and solve.
V2 =
0.410 L ! 348 K
318 K
V2 = 0.45 L
Statement: The sample of argon gas will occupy a volume of 0.45 L at 75 °C.
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Chapter 11: The Gas State and Gas Laws
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Section 11.9: The Gas Laws—Boyle’s Law, Gay-Lussac’s Law, and the Combined
Gas Law, pages 189–191
1. When you inhale, the volume of your lungs increases. When the volume of your lungs increases, the
pressure in your lungs decreases.
2. a
3. False. When helium gas is released from a tank into a balloon, the volume of the balloon increases. This
means that the pressure of the helium decreases.
4. The molecules in the gas will be pushed closer together, increasing their vibrational, translational, and
rotational motion, causing more collisions.
5. Given: P1 = 1.0 kPa; V1 = 0.55 L; V2 = 1.0 L
Required: P2
Analysis: P1 V1 = P2 V2
Solution:
Step 1: Rearrange the equation to isolate P2.
P2 =
PV
1 1
V2
Step 2: Substitute values into the equation and solve.
V2 =
1.0 kPa ! 0.55 L
4.0 L
V2 = 0.14 kPa
Statement: If the volume of the gas is increased to 4.0 L, the pressure of the gas will be 0.14 kPa.
6. The balloon shrinks because as the temperature decreases from the warm house to the cold outdoors, the
volume of the gas inside the balloon decreases. This causes the balloon to deflate.
7. c
8. False. When the temperature of a gas increases, its pressure will increase.
9. An increase in the temperature of a gas will increase its kinetic energy.
10. Given: t1 = 25 °C; P1 = 1.0 Pa; t2 = 75 °C
Required: P2
Analysis:
P1
T1
=
P2
T2
Solution:
Step 1: Convert the temperatures in kelvins.
T1 = t1 + 273
= 25 + 273
T1 = 298 K
T2 = t2 + 273
= 75 + 273
T2 = 348 K
Step 2: Rearrange the equation to isolate P2.
P2 =
PT
1 2
T1
Step 3: Substitute values into the equation and solve.
P2 =
1.0 Pa ! 348 K
298 K
P2 = 1.2 Pa
Statement: If the temperature is increased to 348 K, the final pressure of the gas will be 1.2 Pa.
11. c
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Chapter 11: The Gas State and Gas Laws
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12. Given: P1 = 33.3 kPa; V1 = 0.345 L; t1 = 25 °C; P2 = 40 kPa; V2 = 0.50 L
Required: T2
Analysis:
PV
1 1
T1
=
PV
2 2
T2
Solution:
Step 1: Convert the temperature to kelvins.
T1 = t1 + 273
= 25 + 273
T1 = 298 K
Step 2: Rearrange the equation to solve isolate T2.
T2 =
PV
2 2T1
PV
1 1
Step 3: Substitute values into the equation and solve.
T2 =
40 kPa ! 0.50 L ! 298 K
33.3 kPa ! 0.345 L
T2 = 518.8 K (two extra digits carried)
Step 4: Convert the temperature to the required unit.
T2 = t2 + 273
t2 = T2 ! 273
= 518.8 ! 273
t2 = 250 °C
Statement: When the pressure of the gas is increased to 40 kPa and the volume is increased to 0.50 L, the
temperature of the gas increases to 250 °C.
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Chapter 11: The Gas State and Gas Laws
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Chapter 11 Questions, pages 193–194
1. b
2. d
3. (a) False. Kinetic molecular theory states that entities in solids, liquids, and gases are in constant random
motion.
(b) True
4. The atmosphere is comprised of four layers: the troposphere, the stratosphere, the mesosphere, and the
thermosphere.
5. When a gas cools, the molecules in the gas begin to move more slowly and become less spread apart. This
can be seen in a balloon that is cooled. As the gas cools, the molecules move closer together and the balloon
deflates.
6. Answers may vary. Sample answer:
Figure 1
7. A. Solar radiation is falling to Earth and warming Earth’s surface.
B. Infrared radiation captured by Earth’s surface is being released into the atmosphere.
C. Greenhouse gases are capturing the infrared energy and re-emitting it back to Earth’s surface. This warms
Earth’s surface.
8. (a) Boyle’s law is being illustrated in Figure 3.
(b) When the volume is decreased, the gas molecules exert a greater pressure on the container.
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Chapter 11: The Gas State and Gas Laws
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