Download chemistry - Illini West

CHEMISTRY
CHAPTER
Table Of Contents
13
Matter and Change
Chapter 13: Gases
Section 13.1
The Gas Laws
Section 13.2
The Ideal Gas Law
Section 13.3
Gas Stoichiometry
Click a hyperlink to view the corresponding slides.
SECTION
13.1
The Gas Laws
• 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.
SECTION
Exit
The Gas Laws
13.1
Boyle’s law
absolute zero
Charles’s law
Gay-Lussac’s law
combined gas law
scientific law: describes a relationship in nature that
is supported by many experiments
For a fixed amount of gas, a change in
one variable—pressure, temperature,
or volume—affects the other two.
1
SECTION
The Gas Laws
13.1
SECTION
13.1
The Gas Laws
Charles's Law
Boyle'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
SECTION
13.1
The Gas Laws
Charles's Law (cont.)
Gay-Lussac's Law
• Absolute zero is zero on the Kelvin scale.
• 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.
• Charles’s law states that the volume of a given
amount of gas is directly proportional to its kelvin
temperature at constant pressure.
2
SECTION
The Gas Laws
13.1
SECTION
13.2
The Ideal Gas Law
The Combined Gas Law
• The combined gas law states the
relationship among pressure, temperature,
and volume of a fixed amount of gas.
• 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
SECTION
13.2
The Ideal Gas Law
Avogadro's Principle
Avogadro’s principle
molar volume
ideal gas constant (R)
• Avogadro’s principle states that equal volumes
of gases at the same temperature and pressure
contain equal numbers of particles.
ideal gas law
The ideal gas law relates the number of
particles to pressure, temperature, and
volume.
3
SECTION
13.2
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).
SECTION
13.2
The Ideal Gas Law
The Ideal Gas Law
• Ideal gas particles occupy a negligible volume
and are far enough apart to exert minimal
attractive or repulsive forces on each other.
• Combined gas law to ideal gas law
• At STP, 1 mol of gas occupies 22.4 L.
SECTION
13.2
The Ideal Gas Law
The Ideal Gas Law (cont.)
• The ideal gas constant is represented by R and
is 0.0821 L•atm/mol•K when pressure is in
atmospheres.
• The ideal gas law describes the physical
behavior of an ideal gas in terms of pressure,
volume, temperature, and amount.
SECTION
13.2
The Ideal Gas Law
The Ideal Gas Law—Molar Mass and
Density
• Molar mass and the ideal gas law
4
SECTION
13.2
The Ideal Gas Law
The Ideal Gas Law—Molar Mass and
Density (cont.)
• Density and the ideal gas law
SECTION
13.2
The Ideal Gas Law
Real Versus Ideal Gases
• Ideal gases follow the assumptions of the kineticmolecular theory.
• 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.
SECTION
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
13.3
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.
5
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
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.
6