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CHAPTER
CHEMISTRY
Table Of Contents
13
Matter and Change
Chapter 13: Gases
SECTION
13.1
The Gas Laws
Section 13.1
The Gas Laws
Section 13.2
The Ideal Gas Law
Section 13.3
Gas Stoichiometry
SECTION
The Gas Laws
13.1
Boyle’s law
• State the relationships among pressure, temperature,
and volume of a constant amount of gas.
• Apply the gas laws to problems involving the
pressure, temperature, and volume of a constant
amount of gas.
scientific law: describes a relationship in nature that
is supported by many experiments
absolute zero
Charles’s law
Gay-Lussac’s law
combined gas law
For a fixed amount of gas, a change in
one variable—pressure, temperature,
or volume—affects the other two.
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SECTION
The Gas Laws
13.1
Boyle's Law
SECTION
13.1
The Gas Laws
Charles's Law
• Boyle’s law states that the volume of a fixed
amount of gas held at a constant temperature
varies inversely with the pressure.
• As temperature increases, so does the volume of
gas when the amount of gas and pressure do not
change.
• Kinetic-molecular theory explains this property.
P1V1 = P2V2 where P = pressure and V = volume
SECTION
13.1
The Gas Laws
Charles's Law (cont.)
SECTION
13.1
The Gas Laws
Charles's Law (cont.)
• Absolute zero is zero on the Kelvin scale.
• Charles’s law states that the volume of a given
amount of gas is directly proportional to its kelvin
temperature at constant pressure.
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SECTION
SECTION
13.1
13.1
The Gas Laws
Gay-Lussac's Law
The Gas Laws
Gay-Lussac's Law (cont.)
• Gay-Lussac’s law states that the pressure
of a fixed amount of gas varies directly with
the kelvin temperature when the volume
remains constant.
SECTION
SECTION
13.1
13.1
The Gas Laws
The Combined Gas Law
The Gas Laws
The Combined Gas Law (cont.)
• The combined gas law states the
relationship among pressure, temperature,
and volume of a fixed amount of gas.
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SECTION
13.1
Section Check
SECTION
Section Check
13.1
Boyle’s Law explains which relationship
of properties in gases?
Atoms are in their lowest energy state at
what temperature?
A. pressure and volume
A. 0°Celsius
B. amount and pressure
B. 0°Fahrenheit
C. temperature and volume
C. –100°Celsius
D. volume and temperature
D. 0 kelvin
SECTION
13.2
The Ideal Gas Law
• Relate number of particles and volume using
Avogadro’s principle.
• Relate the amount of gas present to its pressure,
temperature, and volume using the ideal gas law.
• Compare the properties of real and ideal gases.
mole: an SI base unit used to measure the amount of
a substance; the amount of a pure substance that
contains 6.02 × 1023 representative particles
SECTION
The Ideal Gas Law
13.2
Avogadro’s principle
molar volume
ideal gas constant (R)
ideal gas law
The ideal gas law relates the number of
particles to pressure, temperature, and
volume.
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SECTION
SECTION
13.2
13.2
The Ideal Gas Law
Avogadro's Principle
• Avogadro’s principle states that equal volumes
of gases at the same temperature and pressure
contain equal numbers of particles.
The Ideal Gas Law
Avogadro's Principle (cont.)
• The molar volume of a gas is the volume
1 mol occupies at 0.00°C and 1.00 atm of
pressure.
• 0.00°C and 1.00 atm are called standard
temperature and pressure (STP).
• At STP, 1 mol of gas occupies 22.4 L.
SECTION
SECTION
13.2
13.2
The Ideal Gas Law
The Ideal Gas Law
The Ideal Gas Law
The Ideal Gas Law (cont.)
• Ideal gas particles occupy a negligible volume
and are far enough apart to exert minimal
attractive or repulsive forces on each other.
• The ideal gas constant is represented by R and
is 0.0821 L•atm/mol•K when pressure is in
atmospheres.
• Combined gas law to ideal gas law
• The ideal gas law describes the physical
behavior of an ideal gas in terms of pressure,
volume, temperature, and amount.
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SECTION
SECTION
13.2
13.2
The Ideal Gas Law
The Ideal Gas Law (cont.)
The Ideal Gas Law
The Ideal Gas Law—Molar Mass and Density
• Molar mass and the ideal gas law
SECTION
SECTION
13.2
13.2
The Ideal Gas Law
The Ideal Gas Law—Molar Mass and Density
The Ideal Gas Law
Real Versus Ideal Gases
• Ideal gases follow the assumptions of the kineticmolecular theory.
• Density and the ideal gas law
• Characteristics of ideal gases:
– There are no intermolecular attractive or repulsive
forces between particles or with their containers.
– The particles are in constant random motion.
– Collisions are perfectly elastic.
– No gas is truly ideal, but most behave as ideal gases
at a wide range of temperatures and pressures.
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SECTION
SECTION
13.2
13.2
The Ideal Gas Law
Real Versus Ideal Gases (cont.)
• Real gases deviate most from ideal gases at
high pressures and low temperatures.
• Polar molecules have larger attractive forces
between particles.
• Polar gases do not behave as ideal gases.
• Large nonpolar gas particles occupy more space
and deviate more from ideal gases.
SECTION
13.2
Section Check
3.00 mol of O2 at STP occupies how
much volume?
A. 30.0 L
B. 22.4 L
C. 25.4 L
D. 67.2 L
Section Check
Which of the following is NOT one of the
related physical properties described in
the ideal gas law?
A. pressure
B. volume
C. density
D. temperature
SECTION
13.3
Gas Stoichiometry
• Determine volume ratios for gaseous reactants and
products by using coefficients from chemical equations.
• Apply gas laws to calculate amounts of gaseous reactants
and products in a chemical reaction.
coefficient: the number written in front of a reactant or
product in a chemical equation, which tells the smallest
number of particles of the substance involved in the reaction
When gases react, the coefficients in the
balanced chemical equation represent both
molar amounts and relative volumes.
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SECTION
13.3
Gas Stoichiometry
SECTION
13.3
Gas Stoichiometry
Stoichiometry of Reactions Involving Gases
Stoichiometry and Volume-Volume Problems
• The gas laws can be applied to calculate the
stoichiometry of reactions in which gases are
reactants or products.
• Coefficients in a balanced equation represent
volume ratios for gases.
2H2(g) + O2(g) → 2H2O(g)
• 2 mol H2 reacts with 1 mol O2 to produce
2 mol water vapor.
SECTION
13.3
Gas Stoichiometry
SECTION
13.3
Section Check
Stoichiometry and Volume-Mass Problems
• A balanced chemical equation allows you to find
ratios for only moles and gas volumes, not for
masses.
• All masses given must be converted to moles or
volumes before being used as part of a ratio.
How many mol of hydrogen gas are
required to react with 1.50 mol oxygen
gas in the following reaction?
2H2(g) + O2(g) → 2H2O(g)
A. 1.00
B. 2.00
C. 3.00
D. 4.00
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SECTION
Section Check
13.3
SECTION
The Gas Laws
13.1
Study Guide
How many liters of hydrogen gas are
required to react with 3.25 liters of
oxygen gas in the following reaction?
2H2(g) + O2(g) → 2H2O(g)
A. 2.00
Key Concepts
• Boyle’s law states that the volume of a fixed amount of
gas is inversely proportional to its pressure at constant
temperature.
P1V1 = P2V2
• Charles’s law states that the volume of a fixed amount of
gas is directly proportional to its kelvin temperature at
constant pressure.
B. 3.25
C. 4.00
D. 6.50
SECTION
The Gas Laws
13.1
Study Guide
SECTION
The Ideal Gas Law
13.2
Study Guide
Key Concepts
Key Concepts
• Gay-Lussac’s law states that the pressure of a fixed
amount of gas is directly proportional to its kelvin
temperature at constant volume.
• Avogadro’s principle states that equal volumes of gases
at the same pressure and temperature contain equal
numbers of particles.
• The ideal gas law relates the amount of a gas present
to its pressure, temperature, and volume.
• The combined gas law relates pressure, temperature, and
volume in a single statement.
PV = nRT
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SECTION
The Ideal Gas Law
13.2
SECTION
Gas Stoichiometry
13.3
Study Guide
Study Guide
Key Concepts
Key Concepts
• The ideal gas law can be used to find molar mass if the
mass of the gas is known, or the density of the gas if its
molar mass is known.
• The coefficients in a balanced chemical equation specify
volume ratios for gaseous reactants and products.
• The gas laws can be used along with balanced chemical
equations to calculate the amount of a gaseous reactant
or product in a reaction.
• At very high pressures and very low temperatures, real
gases behave differently than ideal gases.
CHAPTER
13
Gases
CHAPTER
13
Gases
Chapter Assessment
Chapter Assessment
What does the combined gas law relate?
A. pressure and temperature
According to Charles’s law, if pressure
and amount of a gas are fixed, what will
happen as temperature is increased?
B. volume and pressure
A. Volume will decrease.
C. pressure, temperature, and volume
B. Volume will increase.
D. pressure, temperature, volume, and amount
C. Mass will increase.
D. Mass will decrease.
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CHAPTER
13
Gases
CHAPTER
13
Gases
Chapter Assessment
Chapter Assessment
Equal volumes of gases at the same
temperature and pressure contain equal
numbers of particles is stated by:
What is the volume of 1.00 mol of chlorine
gas at standard temperature and
pressure?
A. Law of conservation of mass
A. 1.00 L
B. Boyle’s law
B. 18.0 L
C. Avogadro’s principle
C. 22.4 L
D. Ideal gas law
D. 44.8 L
CHAPTER
13
Gases
CHAPTER
13
Gases
Chapter Assessment
Chapter Assessment
When do real gases behave differently
than ideal gases?
If two variables are directly proportional,
what happens to the value of one as the
other decreases?
A. high temperature or low pressure
B. high temperature or high pressure
C. low temperature or low pressure
D. low temperature or high pressure
A. increases
B. decreases
C. remains constant
D. none of the above
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CHAPTER
13
Gases
CHAPTER
13
Gases
Chapter Assessment
Chapter Assessment
What conditions represent standard
temperature and pressure?
One mole of gas occupies how much
volume at STP?
A. 0.00°C and 0.00atm
A. 1.00 L
B. 1.00°C and 1.00atm
B. 2.20 L
C. 0.00°F and 1.00atm
C. 22.4 L
D. 0.00°C and 1.00atm
D. 33.7 L
CHAPTER
13
Gases
CHAPTER
13
Gases
Chapter Assessment
Chapter Assessment
Which of the following would deviate the most
from an ideal gas?
What volume will 3.50 mol of Xe gas
occupy at STP?
A. gas in a hot-air balloon
A. 78.4 L
B. water vapor from the reaction of gaseous
hydrogen and oxygen
B. 22.4 L
C. upper atmospheric gases
C. 25.9 L
D. 54.4 L
D. gases near absolute zero
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