Chapter 14 The Behavior of Gases - PBworksvalverdescience.pbworks.com/w/file/fetch/65204251/Chapter...
Transcript of Chapter 14 The Behavior of Gases - PBworksvalverdescience.pbworks.com/w/file/fetch/65204251/Chapter...
Chapter 14“The Behavior of Gases”
Pre-AP ChemistryCharles Page High School
Stephen L. CottonMonday, April 8, 13
Section 14.1The Properties of Gases
OBJECTIVES:Explain why gases are easier to compress than solids or liquids are.
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Section 14.1The Properties of Gases
OBJECTIVES:Describe the three factors that affect gas pressure.
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Compressibility
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CompressibilityGases can expand to fill its
container, unlike solids or liquids
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CompressibilityGases can expand to fill its
container, unlike solids or liquidsThe reverse is also true:
They are easily compressed, or squeezed into a smaller volume
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CompressibilityGases can expand to fill its
container, unlike solids or liquidsThe reverse is also true:
They are easily compressed, or squeezed into a smaller volume
Compressibility is a measure of how much the volume of matter decreases under pressure
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Compressibility
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CompressibilityThis is the idea behind placing “air
bags” in automobiles
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CompressibilityThis is the idea behind placing “air
bags” in automobilesIn an accident, the air compresses
more than the steering wheel or dash when you strike it
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CompressibilityThis is the idea behind placing “air
bags” in automobilesIn an accident, the air compresses
more than the steering wheel or dash when you strike it
The impact forces the gas particles closer together, because there is a lot of empty space between them
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Variables that describe a Gas
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Variables that describe a Gas The four variables and their common
units:
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Variables that describe a Gas The four variables and their common
units:1. pressure (P) in kilopascals
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Variables that describe a Gas The four variables and their common
units:1. pressure (P) in kilopascals2. volume (V) in Liters
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Variables that describe a Gas The four variables and their common
units:1. pressure (P) in kilopascals2. volume (V) in Liters3. temperature (T) in Kelvin
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Variables that describe a Gas The four variables and their common
units:1. pressure (P) in kilopascals2. volume (V) in Liters3. temperature (T) in Kelvin4. amount (n) in moles
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Variables that describe a Gas The four variables and their common
units:1. pressure (P) in kilopascals2. volume (V) in Liters3. temperature (T) in Kelvin4. amount (n) in moles
• The amount of gas, volume, and temperature are factors that affect gas pressure.
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1. Amount of Gas
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1. Amount of GasWhen we inflate a balloon, we are
adding gas molecules.
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1. Amount of GasWhen we inflate a balloon, we are
adding gas molecules. Increasing the number of gas
particles increases the number of collisionsthus, the pressure increases
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1. Amount of GasWhen we inflate a balloon, we are
adding gas molecules. Increasing the number of gas
particles increases the number of collisionsthus, the pressure increases
If temperature is constant, then doubling the number of particles doubles the pressure
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Pressure and the number of molecules are directly related
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Pressure and the number of molecules are directly related
More molecules means more collisions, and…
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Pressure and the number of molecules are directly related
More molecules means more collisions, and…
Fewer molecules means fewer collisions.
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Pressure and the number of molecules are directly related
More molecules means more collisions, and…
Fewer molecules means fewer collisions.
Gases naturally move from areas of high pressure to low pressure, because there is empty space to move into – a spray can is example.
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2. Volume of Gas
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2. Volume of Gas In a smaller container, the
molecules have less room to move.
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2. Volume of Gas In a smaller container, the
molecules have less room to move.
The particles hit the sides of the container more often.
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2. Volume of Gas In a smaller container, the
molecules have less room to move.
The particles hit the sides of the container more often.
As volume decreases, pressure increases. (think of a syringe)Thus, volume and pressure are
inversely related to each other
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3. Temperature of Gas
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3. Temperature of Gas Raising the temperature of a gas increases
the pressure, if the volume is held constant. (Temp. and Pres. are directly related)The molecules hit the walls harder, and
more frequently!
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3. Temperature of Gas Raising the temperature of a gas increases
the pressure, if the volume is held constant. (Temp. and Pres. are directly related)The molecules hit the walls harder, and
more frequently! Should you throw an aerosol can into a
fire? What could happen?
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3. Temperature of Gas Raising the temperature of a gas increases
the pressure, if the volume is held constant. (Temp. and Pres. are directly related)The molecules hit the walls harder, and
more frequently! Should you throw an aerosol can into a
fire? What could happen? When should your automobile tire pressure
be checked?
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Section 14.2The Gas Laws
OBJECTIVES:Describe the relationships among the temperature, pressure, and volume of a gas.
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Section 14.2The Gas Laws
OBJECTIVES:Use the combined gas law to solve problems.
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The Gas Laws are mathematical
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The Gas Laws are mathematicalThe gas laws will describe HOW
gases behave.Gas behavior can be predicted by
the theory.
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The Gas Laws are mathematicalThe gas laws will describe HOW
gases behave.Gas behavior can be predicted by
the theory.The amount of change can be
calculated with mathematical equations.
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The Gas Laws are mathematicalThe gas laws will describe HOW
gases behave.Gas behavior can be predicted by
the theory.The amount of change can be
calculated with mathematical equations.
You need to know both of these: the theory, and the math
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Robert Boyle(1627-1691)
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Robert Boyle(1627-1691)
• Boyle was born into an aristocratic Irish family
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Robert Boyle(1627-1691)
• Boyle was born into an aristocratic Irish family
• Became interested in medicine and the new science of Galileo and studied chemistry.
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Robert Boyle(1627-1691)
• Boyle was born into an aristocratic Irish family
• Became interested in medicine and the new science of Galileo and studied chemistry.
• A founder and an influential fellow of the Royal Society of London
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Robert Boyle(1627-1691)
• Boyle was born into an aristocratic Irish family
• Became interested in medicine and the new science of Galileo and studied chemistry.
• A founder and an influential fellow of the Royal Society of London
• Wrote extensively on science, philosophy, and theology.
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#1. Boyle’s Law - 1662
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#1. Boyle’s Law - 1662Gas pressure is inversely proportional to the volume, when temperature is held constant.
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#1. Boyle’s Law - 1662
Pressure x Volume = a constant
Gas pressure is inversely proportional to the volume, when temperature is held constant.
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#1. Boyle’s Law - 1662
Pressure x Volume = a constant Equation: P1V1 = P2V2 (T = constant)
Gas pressure is inversely proportional to the volume, when temperature is held constant.
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#1. Boyle’s Law - 1662
Pressure x Volume = a constant Equation: P1V1 = P2V2 (T = constant)
Gas pressure is inversely proportional to the volume, when temperature is held constant.
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Graph of Boyle’s Law – page 418
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Graph of Boyle’s Law – page 418Boyle’s Law says the pressure is inverse to the volume.
Note that when the volume goes up, the pressure goes down
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Jacques Charles (1746-1823)
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Jacques Charles (1746-1823)• French Physicist
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Jacques Charles (1746-1823)• French Physicist• Part of a scientific
balloon flight on Dec. 1, 1783 – was one of three passengers in the second balloon ascension that carried humans
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Jacques Charles (1746-1823)• French Physicist• Part of a scientific
balloon flight on Dec. 1, 1783 – was one of three passengers in the second balloon ascension that carried humans
• This is how his interest in gases started
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Jacques Charles (1746-1823)• French Physicist• Part of a scientific
balloon flight on Dec. 1, 1783 – was one of three passengers in the second balloon ascension that carried humans
• This is how his interest in gases started
• It was a hydrogen filled balloon – good thing they were careful!
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#2. Charles’s Law - 1787
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#2. Charles’s Law - 1787The volume of a fixed mass of gas is directly proportional to the Kelvin temperature, when pressure is held constant.
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#2. Charles’s Law - 1787The volume of a fixed mass of gas is directly proportional to the Kelvin temperature, when pressure is held constant.This extrapolates to zero volume at a temperature of zero Kelvin.
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#2. Charles’s Law - 1787The volume of a fixed mass of gas is directly proportional to the Kelvin temperature, when pressure is held constant.This extrapolates to zero volume at a temperature of zero Kelvin.
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Converting Celsius to Kelvin
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Converting Celsius to Kelvin•Gas law problems involving temperature will always require that the temperature be in Kelvin. (Remember that no degree sign is shown with the kelvin scale.)
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Converting Celsius to Kelvin•Gas law problems involving temperature will always require that the temperature be in Kelvin. (Remember that no degree sign is shown with the kelvin scale.)
•Reason? There will never be a zero volume, since we have never reached absolute zero.
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Converting Celsius to Kelvin•Gas law problems involving temperature will always require that the temperature be in Kelvin. (Remember that no degree sign is shown with the kelvin scale.)
•Reason? There will never be a zero volume, since we have never reached absolute zero.
Kelvin = °C + 273Monday, April 8, 13
Converting Celsius to Kelvin•Gas law problems involving temperature will always require that the temperature be in Kelvin. (Remember that no degree sign is shown with the kelvin scale.)
•Reason? There will never be a zero volume, since we have never reached absolute zero.
Kelvin = °C + 273 and
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Converting Celsius to Kelvin•Gas law problems involving temperature will always require that the temperature be in Kelvin. (Remember that no degree sign is shown with the kelvin scale.)
•Reason? There will never be a zero volume, since we have never reached absolute zero.
Kelvin = °C + 273 °C = Kelvin - 273and
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- Page 421
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Joseph Louis Gay-Lussac (1778 – 1850)
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Joseph Louis Gay-Lussac (1778 – 1850) French chemist and physicist
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Joseph Louis Gay-Lussac (1778 – 1850) French chemist and physicist Known for his studies on the physical properties of gases.
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Joseph Louis Gay-Lussac (1778 – 1850) French chemist and physicist Known for his studies on the physical properties of gases. In 1804 he made balloon ascensions to study magnetic forces and to observe the composition and temperature of the air at different altitudes.
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#3. Gay-Lussac’s Law - 1802
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#3. Gay-Lussac’s Law - 1802•The pressure and Kelvin temperature of a gas are directly proportional, provided that the volume remains constant.
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#3. Gay-Lussac’s Law - 1802•The pressure and Kelvin temperature of a gas are directly proportional, provided that the volume remains constant.
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#3. Gay-Lussac’s Law - 1802•The pressure and Kelvin temperature of a gas are directly proportional, provided that the volume remains constant.
•How does a pressure cooker affect the time needed to cook food? (Note page 422)
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#3. Gay-Lussac’s Law - 1802•The pressure and Kelvin temperature of a gas are directly proportional, provided that the volume remains constant.
•How does a pressure cooker affect the time needed to cook food? (Note page 422)
•Sample Problem 14.3, page 423Monday, April 8, 13
#4. The Combined Gas Law
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#4. The Combined Gas LawThe combined gas law expresses the relationship between pressure, volume and temperature of a fixed amount of gas.
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#4. The Combined Gas LawThe combined gas law expresses the relationship between pressure, volume and temperature of a fixed amount of gas.
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#4. The Combined Gas LawThe combined gas law expresses the relationship between pressure, volume and temperature of a fixed amount of gas.
Sample Problem 14.4, page 424
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The combined gas law contains all the other gas laws!
If the temperature remains constant...
P1 V1
T1
x=
P2 V2
T2
x
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The combined gas law contains all the other gas laws!
If the temperature remains constant...
P1 V1
T1
x=
P2 V2
T2
x
Monday, April 8, 13
The combined gas law contains all the other gas laws!
If the temperature remains constant...
P1 V1
T1
x=
P2 V2
T2
x
Monday, April 8, 13
The combined gas law contains all the other gas laws!
If the temperature remains constant...
P1 V1
T1
x=
P2 V2
T2
x
Boyle’s Law
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The combined gas law contains all the other gas laws!
If the pressure remains constant...
P1 V1
T1
x=
P2 V2
T2
x
Monday, April 8, 13
The combined gas law contains all the other gas laws!
If the pressure remains constant...
P1 V1
T1
x=
P2 V2
T2
x
Monday, April 8, 13
The combined gas law contains all the other gas laws!
If the pressure remains constant...
P1 V1
T1
x=
P2 V2
T2
x
Monday, April 8, 13
The combined gas law contains all the other gas laws!
If the pressure remains constant...
P1 V1
T1
x=
P2 V2
T2
x
Charles’s Law
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u The combined gas law contains all the other gas laws!
u If the volume remains constant...
P1 V1
T1
x=
P2 V2
T2
x
Monday, April 8, 13
u The combined gas law contains all the other gas laws!
u If the volume remains constant...
P1 V1
T1
x=
P2 V2
T2
x
Monday, April 8, 13
u The combined gas law contains all the other gas laws!
u If the volume remains constant...
P1 V1
T1
x=
P2 V2
T2
x
Monday, April 8, 13
u The combined gas law contains all the other gas laws!
u If the volume remains constant...
P1 V1
T1
x=
P2 V2
T2
x
Gay-Lussac’s Law
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Section 14.3Ideal Gases
OBJECTIVES:Compute the value of an unknown using the ideal gas law.
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Section 14.3Ideal Gases
OBJECTIVES:Compare and contrast real an ideal gases.
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5. The Ideal Gas Law #1
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5. The Ideal Gas Law #1 Equation: P x V = n x R x T
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5. The Ideal Gas Law #1 Equation: P x V = n x R x T Pressure times Volume equals the
number of moles (n) times the Ideal Gas Constant (R) times the Temperature in Kelvin.
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5. The Ideal Gas Law #1 Equation: P x V = n x R x T Pressure times Volume equals the
number of moles (n) times the Ideal Gas Constant (R) times the Temperature in Kelvin.
R = 8.31 (L x kPa) / (mol x K)
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5. The Ideal Gas Law #1 Equation: P x V = n x R x T Pressure times Volume equals the
number of moles (n) times the Ideal Gas Constant (R) times the Temperature in Kelvin.
R = 8.31 (L x kPa) / (mol x K) The other units must match the value of
the constant, in order to cancel out.
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5. The Ideal Gas Law #1 Equation: P x V = n x R x T Pressure times Volume equals the
number of moles (n) times the Ideal Gas Constant (R) times the Temperature in Kelvin.
R = 8.31 (L x kPa) / (mol x K) The other units must match the value of
the constant, in order to cancel out. The value of R could change, if other
units of measurement are used for the other values (namely pressure changes)
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The Ideal Gas Law
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We now have a new way to count moles (the amount of matter), by measuring T, P, and V. We aren’t restricted to only STP conditions:
The Ideal Gas Law
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We now have a new way to count moles (the amount of matter), by measuring T, P, and V. We aren’t restricted to only STP conditions:
P x V R x T
The Ideal Gas Law
n =
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Ideal Gases
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Ideal Gases We are going to assume the gases
behave “ideally”- in other words, they obey the Gas Laws under all conditions of temperature and pressure
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Ideal Gases We are going to assume the gases
behave “ideally”- in other words, they obey the Gas Laws under all conditions of temperature and pressure
An ideal gas does not really exist, but it makes the math easier and is a close approximation.
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Ideal Gases We are going to assume the gases
behave “ideally”- in other words, they obey the Gas Laws under all conditions of temperature and pressure
An ideal gas does not really exist, but it makes the math easier and is a close approximation.
Particles have no volume? Wrong!
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Ideal Gases We are going to assume the gases
behave “ideally”- in other words, they obey the Gas Laws under all conditions of temperature and pressure
An ideal gas does not really exist, but it makes the math easier and is a close approximation.
Particles have no volume? Wrong! No attractive forces? Wrong!
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Ideal Gases
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Ideal GasesThere are no gases for which this
is true (acting “ideal”); however,
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Ideal GasesThere are no gases for which this
is true (acting “ideal”); however,Real gases behave this way at
a) high temperature, and b) low pressure.
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Ideal GasesThere are no gases for which this
is true (acting “ideal”); however,Real gases behave this way at
a) high temperature, and b) low pressure.Because at these conditions, a gas will stay a gas!
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35
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36
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40
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#6. Ideal Gas Law 2
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#6. Ideal Gas Law 2 P x V = m x R x T
M
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#6. Ideal Gas Law 2 P x V = m x R x T
M Allows LOTS of calculations, and
some new items are:
Monday, April 8, 13
#6. Ideal Gas Law 2 P x V = m x R x T
M Allows LOTS of calculations, and
some new items are: m = mass, in grams
Monday, April 8, 13
#6. Ideal Gas Law 2 P x V = m x R x T
M Allows LOTS of calculations, and
some new items are: m = mass, in grams M = molar mass, in g/mol
Monday, April 8, 13
#6. Ideal Gas Law 2 P x V = m x R x T
M Allows LOTS of calculations, and
some new items are: m = mass, in grams M = molar mass, in g/mol
Molar mass = m R T P V
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42
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Tro's Introductory Chemistry, Chapter 11
111
Molar Mass of a Gas
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Tro's Introductory Chemistry, Chapter 11
111
Molar Mass of a Gas
• One of the methods chemists use to determine the molar mass of an unknown substance is to heat a weighed sample until it becomes a gas, measure the temperature, pressure, and volume, and use the ideal gas law.
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Tro's Introductory Chemistry, Chapter 11
111
Molar Mass of a Gas
• One of the methods chemists use to determine the molar mass of an unknown substance is to heat a weighed sample until it becomes a gas, measure the temperature, pressure, and volume, and use the ideal gas law.
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Density
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Density Density is mass divided by volume
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Density Density is mass divided by volume
mD =
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Density Density is mass divided by volume
m VD =
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Density Density is mass divided by volume
m Vso, m M P V R T
D =
D = =
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Tro's Introductory Chemistry, Chapter 11
84
Avogadro’s Law
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Tro's Introductory Chemistry, Chapter 11
84
Avogadro’s Law• Volume is directly proportional to
the number of gas molecules.V = constant x n.Constant P and T.More gas molecules = larger
volume.
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Tro's Introductory Chemistry, Chapter 11
84
Avogadro’s Law• Volume is directly proportional to
the number of gas molecules.V = constant x n.Constant P and T.More gas molecules = larger
volume.• Count number of gas molecules
by moles, n.
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Tro's Introductory Chemistry, Chapter 11
84
Avogadro’s Law• Volume is directly proportional to
the number of gas molecules.V = constant x n.Constant P and T.More gas molecules = larger
volume.• Count number of gas molecules
by moles, n.• Equal volumes of gases contain
equal numbers of molecules.The gas doesn’t matter.
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Tro's Introductory Chemistry, Chapter 11
84
Avogadro’s Law• Volume is directly proportional to
the number of gas molecules.V = constant x n.Constant P and T.More gas molecules = larger
volume.• Count number of gas molecules
by moles, n.• Equal volumes of gases contain
equal numbers of molecules.The gas doesn’t matter.
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Tro's Introductory Chemistry, Chapter 11
85
Avogadro’s Law, Continued
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Example 11.5—A 0.22 Mol Sample of He Has a Volume of 4.8 L. How Many Moles Must Be Added to Give 6.4 L?
Check:
Solution:
Solution Map:
Relationships:
Given:
Find:
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Example 11.5—A 0.22 Mol Sample of He Has a Volume of 4.8 L. How Many Moles Must Be Added to Give 6.4 L?
V1 =4.8 L, V2 = 6.4 L, n1 = 0.22 mol
Check:
Solution:
Solution Map:
Relationships:
Given:
Find:
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Example 11.5—A 0.22 Mol Sample of He Has a Volume of 4.8 L. How Many Moles Must Be Added to Give 6.4 L?
V1 =4.8 L, V2 = 6.4 L, n1 = 0.22 mol
n2, and added moles
Check:
Solution:
Solution Map:
Relationships:
Given:
Find:
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Example 11.5—A 0.22 Mol Sample of He Has a Volume of 4.8 L. How Many Moles Must Be Added to Give 6.4 L?
V1 =4.8 L, V2 = 6.4 L, n1 = 0.22 mol
n2, and added moles
Check:
Solution:
Solution Map:
Relationships:
Given:
Find:
V1, V2, n1 n2
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mol added = n2 – n1,
Example 11.5—A 0.22 Mol Sample of He Has a Volume of 4.8 L. How Many Moles Must Be Added to Give 6.4 L?
V1 =4.8 L, V2 = 6.4 L, n1 = 0.22 mol
n2, and added moles
Check:
Solution:
Solution Map:
Relationships:
Given:
Find:
V1, V2, n1 n2
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mol added = n2 – n1,
Example 11.5—A 0.22 Mol Sample of He Has a Volume of 4.8 L. How Many Moles Must Be Added to Give 6.4 L?
V1 =4.8 L, V2 = 6.4 L, n1 = 0.22 mol
n2, and added moles
Check:
Solution:
Solution Map:
Relationships:
Given:
Find:
V1, V2, n1 n2
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mol added = n2 – n1,
Example 11.5—A 0.22 Mol Sample of He Has a Volume of 4.8 L. How Many Moles Must Be Added to Give 6.4 L?
V1 =4.8 L, V2 = 6.4 L, n1 = 0.22 mol
n2, and added moles
Check:
Solution:
Solution Map:
Relationships:
Given:
Find:
V1, V2, n1 n2
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mol added = n2 – n1,
Example 11.5—A 0.22 Mol Sample of He Has a Volume of 4.8 L. How Many Moles Must Be Added to Give 6.4 L?
V1 =4.8 L, V2 = 6.4 L, n1 = 0.22 mol
n2, and added moles
Check:
Solution:
Solution Map:
Relationships:
Given:
Find:
V1, V2, n1 n2
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mol added = n2 – n1,
Example 11.5—A 0.22 Mol Sample of He Has a Volume of 4.8 L. How Many Moles Must Be Added to Give 6.4 L?
V1 =4.8 L, V2 = 6.4 L, n1 = 0.22 mol
n2, and added moles
Check:
Solution:
Solution Map:
Relationships:
Given:
Find:
V1, V2, n1 n2
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mol added = n2 – n1,
Example 11.5—A 0.22 Mol Sample of He Has a Volume of 4.8 L. How Many Moles Must Be Added to Give 6.4 L?
Since n and V are directly proportional, when the volume increases, the moles should increase, and it does.
V1 =4.8 L, V2 = 6.4 L, n1 = 0.22 mol
n2, and added moles
Check:
Solution:
Solution Map:
Relationships:
Given:
Find:
V1, V2, n1 n2
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Tro's Introductory Chemistry, Chapter 11
95
Practice—If 1.00 Mole of a Gas Occupies 22.4 L at STP, What Volume Would 0.750 Moles Occupy?
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Practice—If 1.00 Mole of a Gas Occupies 22.4 L at STP, What Volume Would 0.750 Moles Occupy?, Continued
Check:
Solution:
Solution Map:
Relationships:
Given:
Find:
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Practice—If 1.00 Mole of a Gas Occupies 22.4 L at STP, What Volume Would 0.750 Moles Occupy?, Continued
V1 =22.4 L, n1 = 1.00 mol, n2 = 0.750 mol
Check:
Solution:
Solution Map:
Relationships:
Given:
Find:
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Practice—If 1.00 Mole of a Gas Occupies 22.4 L at STP, What Volume Would 0.750 Moles Occupy?, Continued
V1 =22.4 L, n1 = 1.00 mol, n2 = 0.750 mol
V2
Check:
Solution:
Solution Map:
Relationships:
Given:
Find:
Monday, April 8, 13
Practice—If 1.00 Mole of a Gas Occupies 22.4 L at STP, What Volume Would 0.750 Moles Occupy?, Continued
V1 =22.4 L, n1 = 1.00 mol, n2 = 0.750 mol
V2
Check:
Solution:
Solution Map:
Relationships:
Given:
Find:
V1, n1, n2 V2
Monday, April 8, 13
Practice—If 1.00 Mole of a Gas Occupies 22.4 L at STP, What Volume Would 0.750 Moles Occupy?, Continued
V1 =22.4 L, n1 = 1.00 mol, n2 = 0.750 mol
V2
Check:
Solution:
Solution Map:
Relationships:
Given:
Find:
V1, n1, n2 V2
Monday, April 8, 13
Practice—If 1.00 Mole of a Gas Occupies 22.4 L at STP, What Volume Would 0.750 Moles Occupy?, Continued
V1 =22.4 L, n1 = 1.00 mol, n2 = 0.750 mol
V2
Check:
Solution:
Solution Map:
Relationships:
Given:
Find:
V1, n1, n2 V2
Monday, April 8, 13
Practice—If 1.00 Mole of a Gas Occupies 22.4 L at STP, What Volume Would 0.750 Moles Occupy?, Continued
V1 =22.4 L, n1 = 1.00 mol, n2 = 0.750 mol
V2
Check:
Solution:
Solution Map:
Relationships:
Given:
Find:
V1, n1, n2 V2
Monday, April 8, 13
Practice—If 1.00 Mole of a Gas Occupies 22.4 L at STP, What Volume Would 0.750 Moles Occupy?, Continued
V1 =22.4 L, n1 = 1.00 mol, n2 = 0.750 mol
V2
Check:
Solution:
Solution Map:
Relationships:
Given:
Find:
V1, n1, n2 V2
Monday, April 8, 13
Practice—If 1.00 Mole of a Gas Occupies 22.4 L at STP, What Volume Would 0.750 Moles Occupy?, Continued
Since n and V are directly proportional, when the moles decreases, the volume should decrease, and it does.
V1 =22.4 L, n1 = 1.00 mol, n2 = 0.750 mol
V2
Check:
Solution:
Solution Map:
Relationships:
Given:
Find:
V1, n1, n2 V2
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Real Gasesand
Ideal Gases
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Ideal Gases don’t exist, because:
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Ideal Gases don’t exist, because:
1. Molecules do take up space
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Ideal Gases don’t exist, because:
1. Molecules do take up space2. There are attractive forces between
particles- otherwise there would be no liquids formed
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Real Gases behave like Ideal Gases...
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Real Gases behave like Ideal Gases...
When the molecules are far apart.
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Real Gases behave like Ideal Gases...
When the molecules are far apart.
The molecules do not take up as big a percentage of the space We can ignore the particle
volume.
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Real Gases behave like Ideal Gases...
When the molecules are far apart.
The molecules do not take up as big a percentage of the space We can ignore the particle
volume. This is at low pressure
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Real Gases behave like Ideal Gases…
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Real Gases behave like Ideal Gases…
When molecules are moving fast
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Real Gases behave like Ideal Gases…
When molecules are moving fastThis is at high temperature
Monday, April 8, 13
Real Gases behave like Ideal Gases…
When molecules are moving fastThis is at high temperature
Collisions are harder and faster.
Monday, April 8, 13
Real Gases behave like Ideal Gases…
When molecules are moving fastThis is at high temperature
Collisions are harder and faster.Molecules are not next to each
other very long.
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Real Gases behave like Ideal Gases…
When molecules are moving fastThis is at high temperature
Collisions are harder and faster.Molecules are not next to each
other very long.Attractive forces can’t play a role.
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Section 14.4Gases: Mixtures and Movements OBJECTIVES:
Relate the total pressure of a mixture of gases to the partial pressures of the component gases.
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Section 14.4Gases: Mixtures and Movements OBJECTIVES:
Explain how the molar mass of a gas affects the rate at which the gas diffuses and effuses.
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#7 Dalton’s Law of Partial Pressures
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#7 Dalton’s Law of Partial Pressures
For a mixture of gases in a container,
PTotal = P1 + P2 + P3 + . . .
Monday, April 8, 13
#7 Dalton’s Law of Partial Pressures
For a mixture of gases in a container,
PTotal = P1 + P2 + P3 + . . .
•P1 represents the “partial pressure”, or the contribution by that gas.
Monday, April 8, 13
#7 Dalton’s Law of Partial Pressures
For a mixture of gases in a container,
PTotal = P1 + P2 + P3 + . . .
•P1 represents the “partial pressure”, or the contribution by that gas.•Dalton’s Law is particularly useful in calculating the pressure of gases collected over water.
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Collecting a gas over water – one of the experiments in Chapter 14 involves this.
Connected to gas generator
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If the first three containers are all put into the fourth, we can find the pressure in that container by adding up the pressure in the first 3:
1 2 3 4
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If the first three containers are all put into the fourth, we can find the pressure in that container by adding up the pressure in the first 3:
2 atm + 1 atm + 3 atm
1 2 3 4
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If the first three containers are all put into the fourth, we can find the pressure in that container by adding up the pressure in the first 3:
2 atm + 1 atm + 3 atm = 6 atm
1 2 3 4
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If the first three containers are all put into the fourth, we can find the pressure in that container by adding up the pressure in the first 3:
2 atm + 1 atm + 3 atm = 6 atm
Sample Problem 14.6, page 434
1 2 3 4
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Diffusion is:
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Diffusion is:u Molecules moving from areas of high
concentration to low concentration.
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Diffusion is:u Molecules moving from areas of high
concentration to low concentration.uExample: perfume molecules spreading across the room.
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Diffusion is:
Effusion: Gas escaping through a tiny hole in a container.
u Molecules moving from areas of high concentration to low concentration.uExample: perfume molecules spreading across the room.
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Diffusion is:
Effusion: Gas escaping through a tiny hole in a container.
Both of these depend on the molar mass of the particle, which determines the speed.
u Molecules moving from areas of high concentration to low concentration.uExample: perfume molecules spreading across the room.
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Monday, April 8, 13
•Diffusion: describes the mixing of gases. The rate of diffusion is the rate of gas mixing.
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•Diffusion: describes the mixing of gases. The rate of diffusion is the rate of gas mixing.
•Molecules move from areas of high concentration to low concentration.
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•Diffusion: describes the mixing of gases. The rate of diffusion is the rate of gas mixing.
•Molecules move from areas of high concentration to low concentration.
•Fig. 14.18, p. 435Monday, April 8, 13
Monday, April 8, 13
Effusion: a gas escapes through a tiny hole in its container
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Effusion: a gas escapes through a tiny hole in its container
Diffusion and effusion are explained by the next gas law: Graham’s
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8. Graham’s LawRateA √ MassB
RateB √ MassA
=
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8. Graham’s Law
The rate of effusion and diffusion is inversely proportional to the square root of the molar mass of the molecules.
RateA √ MassB
RateB √ MassA
=
Monday, April 8, 13
8. Graham’s Law
The rate of effusion and diffusion is inversely proportional to the square root of the molar mass of the molecules.
Derived from: Kinetic energy = 1/2 mv2
RateA √ MassB
RateB √ MassA
=
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8. Graham’s Law
The rate of effusion and diffusion is inversely proportional to the square root of the molar mass of the molecules.
Derived from: Kinetic energy = 1/2 mv2
m = the molar mass, and v = the velocity.
RateA √ MassB
RateB √ MassA
=
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Graham’s Law
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Sample: compare rates of effusion of Helium with Nitrogen – done on p. 436
Graham’s Law
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Sample: compare rates of effusion of Helium with Nitrogen – done on p. 436
With effusion and diffusion, the type of particle is important: Gases of lower molar mass diffuse and
effuse faster than gases of higher molar mass.
Graham’s Law
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Sample: compare rates of effusion of Helium with Nitrogen – done on p. 436
With effusion and diffusion, the type of particle is important: Gases of lower molar mass diffuse and
effuse faster than gases of higher molar mass.
Helium effuses and diffuses faster than nitrogen – thus, helium escapes from a balloon quicker than many other gases!
Graham’s Law
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End of Chapter 14
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