Chapter 13: Gases
Gas Laws
Main Concepts:
Boyle's Law:
*objective: to understand how to relate pressure and volume of a gas.
*Scientist Robert Boyle
*J-shaped tube which was closed at one end.
*pressure increases and the volume of the gas that is trapped decreases
*using pv=pv you can see a better relationship of the pressure and volume in experiments
*For Boyle's Law to hold, the amount of gas (moles) must not be changed. The temperature must also be constant. *Boyle’s Law: pressure and volume are inversely proportional
*If one doubles, the other decreases by one-half
*PV = PV
equation: P1V1= P2V2
Charles's Law:
*objective: learn about absolute zero; learn about the relation between volume and temperature of a sample gas at constant moles and pressure
*Volume of a given amount of gas at constant pressure will increase w/ the temperature of the gas
*Temperature increases --> volume increases
*Temperature decreases --> volume decreases
*Volume cannot be 0 or negative
*V1 = V2
*T1 = T2
Combined Gas Law
*This law combines both Boyle’s Law and Charles’s Law
*P1V1 = P2V2/T2
*T1 = T2
*A 2.0 L sample of air is collected at 298 K and then cooled to 278 K. Pressure is held constant. How doe the new volume change.
** Volume decreases b/c temperature decreases
*A sample of gas at 15℃ has a volume of 2.58 L. The temperature is raised to 38℃. Pressure is held constant. How does the new volume change.
** Volume of gas increases
*pv/t=pv/t
Ideal Gas Law
*PV = nRT
*R = universal gas constant (0.08206 L * atm/(mol * K)
*Derived from observation of Boyle’s, Charles’s, and Avogadro’s Laws
*R= universal gas constant (0.08206 L atm/mol
*P= pressure
*V= volume
*n= moles
*T= temperature
*PV=nRT
Avogadro's Law:
*the relationship between the volume of a gas and the number of molecules present in the gas sample
*if the number of moles increases, then the volume should also increase
*temperature and pressure are constant
*v/n=v/n
Website:
http://www.chm.davidson.edu/vce/Gaslaws/index.html
*This website helps to determine between the different gas laws.
Activity:
http://quizlet.com/1901741/gas-laws-flash-cards/
*This activity helps to recognize the different gas laws.
Calculations:
1) How many moles of gas does it take to occupy 120 liters at a pressure of 2.3 atmospheres and a temperature of 340 K?
to solve the equation use: Pv=nRt because you are solving for moles and have one of each of the other variables to the equation:
p=2.3
v=120L
n=?
R= 0.08206
t= 340K
Pv=nRt...........PV/RT=N
(2.3) (120) = 276 = 10 mole
(0.08206)(340) 27.9
2) If I have a 50. Liter container that holds 45 moles of gas at a temperature of 200 degrees C, what is the pressure inside the container?
to solve the equation use: Pv=nRt
p=?
v= 50. L
n=45
R=0.08206
t= 200 degrees C (must change to K so, 273.15 + 200 = 473.15 K)
p=nrt/v
p= (45)(0.08206)(473.15) = 34.94= 35 ATM
50
Video:
http://www.youtube.com/watch?v=BxUS1K7xu30
*This video explains again what a gas is and then explains the ideal gas law, Boyle's Law, etc.
Assumptions of the gas laws:
Main Concepts
Boyle's :
1. Temperature is constant
2. Number of moles is constant
Charles's:
1. Pressure is held constant
2. Number of atoms/molecules stays constant
Combined:
number of moles is constant
Ideal:
gas is ideal
Avogradro's:
perfect ideal gas
Pressures:
Main Concepts:
*Atm: standart atmosphere pressure
*atmospheric pressure is measured by the barometer
*conversions:
- 1 atm = 760 torr
- 1 atm = 760 mm Hg
- 1 atm = 14.7 psi (pounds per square inch)
- 1 atm = 101,325 Pa (pascal): SI unit for pressure
Calculations:
1) If the pressure of a sample is 934509 Pa, what is the pressure in atm?
1atm= 101,325 Pa
934509 Pa x 1 atm = 9.22289 atm
101,352 Pa
*the Pa will divide out leaving you with atm and then you plug it in to your calculator to find the answer in atm.
2) What is the pressure of the gas tank in torr, if the pressure was 1, 532 mm Hg?
1532 mm Hg x 1 atm x 760 torr = 1532 torr
760 mm Hg 1 atm
*the mm Hg and the atm divide out leaving you left with torr and the ability to plug it in and get your answer.
Activity:
http://quizlet.com/21917939/chemistry-gas-conversions-and-constants-flash-cards/
*This quizlet helps to identify each gas conversion with the correct number that goes along with the conversion factor.
Video:
http://www.youtube.com/watch?v=CX0__XRqrcg
*This video goes over STP which will be discussed further down as well as the conversions with pressure
Absolute Zero:
Main Concepts:
* Absolute zero is the bottom temperature where it can no longer get any colder. This is seen when volume decreases and temperature decreases as well. Because of absolute zero, an object can never have negative or zero volume. It is impossible.
Website:
http://www.colorado.edu/physics/2000/bec/temperature.html
*This is a fun, helpful website to help you better understand the concept of absolute zero.
Video:
http://www.youtube.com/watch?v=JHXxPnmyDbk
*This video again re-enforces the concept of absolute zero and why it is such a thing.
Dalton's Law of Partial Pressure:
Main Concepts:
*the relationship between the partial and total pressure of gas mixture in calculations
*Studies have shown that each component of a gas mixture behaves independently
*John Dalton was one of the first scientist to study it
*The partial pressure of a gas is the pressure that the gas would exert if it were alone in the container
*The total pressure is the total of all the pressures present in the container
*Ptotal = P1 + P2 + P3
Calculation:
Ptotal = P1 + P2 + P3
1) A sample of Oxygen gas is saturated with water vapor at 27 degrees C. The total pressure of the mixture was 772 torr and the water vapor pressure is 267 at 27 degrees C. What is the partial pressure of the Oxygen gas?
Ptotal= P1 + P2 ......... Ptotal - P1 = P2
772 torr - 267 torr = P2
P2= 505 torr
Activity:
http://quizlet.com/5876954/ap-ii-quiz-4-flash-cards/
*This is an activity about the partial pressure law by Dalton.
Video:
http://www.youtube.com/watch?v=RqffPYOoxd8
*This video explains how to apply Dalton's Law of Partia Pressure
The Kinetic Molecular Theory of Gases:
Main Concept:
*understand the term temperature
*qualitative relationships between the KM theory and the properties of gases
*the temperature of a gas reflects how rapidly, on average, its individual gas particles are moving
*At high temps the particles move very fast and hit the walls of the container frequently
* At low temps the particles motion is more sluggish and they collide with the walls of the container much less often
*temperature is a measure of the motion of the gas particles
*pressure is due to the collision with the walls of the container so therefor as the temperature increases the pressure will increase
Website:
http://www.chm.davidson.edu/vce/kineticmoleculartheory/basicconcepts.html
*This website explains the postulates and behave of gases that are present in this law.
Video:
http://www.youtube.com/watch?v=8jelON52wMw
*This video explains the Kinetic Molecular Theory of Gases with a model and labels it and show what happens to make this law true
Gas Stoichiometry and STP:
Main Concept:
*understand the molar volume of an ideal gas
*molar volume= 22.4 L
*always deals with stoichiometry problems involving gases
* this is so because it is under certain conditions that make it at STP.
*definition of STP
*standard temperature pressure
*0 degrees C and 1 atm
*properties of gases are usually given under these conditions
*molar volume of ideal gas at STP is 22.4 L
*Ideal Gas equation
*pv=nrt
Website:
http://www.chemtutor.com/gases.htm
*This website covers the gas law stoichiometry along with the other laws that were previously discussed within the chapter.
Activity:
http://quizlet.com/1656417/gas-laws-stoichiometry-flash-cards/
*This quizlet helps to identify STP and the stoichiometry process.
http://www.allbookez.com/ideal-gas-law-and-stoichiometry-answer-key/
*This website has a bunch of gas law stoichiometry worksheets to practice with along with answers so you can see if you are completing them right.
Video:
http://www.youtube.com/watch?v=XrrKXzghxAQ
*This video discusses how to solve gas law stoichiometry with problems not at STP.
http://www.youtube.com/watch?v=08TkB_eBQS8
*This video highlights gases that are at STP during stoichiometry.
Calculations:
Main Concepts:
Boyle's Law:
*objective: to understand how to relate pressure and volume of a gas.
*Scientist Robert Boyle
*J-shaped tube which was closed at one end.
*pressure increases and the volume of the gas that is trapped decreases
*using pv=pv you can see a better relationship of the pressure and volume in experiments
*For Boyle's Law to hold, the amount of gas (moles) must not be changed. The temperature must also be constant. *Boyle’s Law: pressure and volume are inversely proportional
*If one doubles, the other decreases by one-half
*PV = PV
equation: P1V1= P2V2
Charles's Law:
*objective: learn about absolute zero; learn about the relation between volume and temperature of a sample gas at constant moles and pressure
*Volume of a given amount of gas at constant pressure will increase w/ the temperature of the gas
*Temperature increases --> volume increases
*Temperature decreases --> volume decreases
*Volume cannot be 0 or negative
*V1 = V2
*T1 = T2
Combined Gas Law
*This law combines both Boyle’s Law and Charles’s Law
*P1V1 = P2V2/T2
*T1 = T2
*A 2.0 L sample of air is collected at 298 K and then cooled to 278 K. Pressure is held constant. How doe the new volume change.
** Volume decreases b/c temperature decreases
*A sample of gas at 15℃ has a volume of 2.58 L. The temperature is raised to 38℃. Pressure is held constant. How does the new volume change.
** Volume of gas increases
*pv/t=pv/t
Ideal Gas Law
*PV = nRT
*R = universal gas constant (0.08206 L * atm/(mol * K)
*Derived from observation of Boyle’s, Charles’s, and Avogadro’s Laws
*R= universal gas constant (0.08206 L atm/mol
*P= pressure
*V= volume
*n= moles
*T= temperature
*PV=nRT
Avogadro's Law:
*the relationship between the volume of a gas and the number of molecules present in the gas sample
*if the number of moles increases, then the volume should also increase
*temperature and pressure are constant
*v/n=v/n
Website:
http://www.chm.davidson.edu/vce/Gaslaws/index.html
*This website helps to determine between the different gas laws.
Activity:
http://quizlet.com/1901741/gas-laws-flash-cards/
*This activity helps to recognize the different gas laws.
Calculations:
1) How many moles of gas does it take to occupy 120 liters at a pressure of 2.3 atmospheres and a temperature of 340 K?
to solve the equation use: Pv=nRt because you are solving for moles and have one of each of the other variables to the equation:
p=2.3
v=120L
n=?
R= 0.08206
t= 340K
Pv=nRt...........PV/RT=N
(2.3) (120) = 276 = 10 mole
(0.08206)(340) 27.9
2) If I have a 50. Liter container that holds 45 moles of gas at a temperature of 200 degrees C, what is the pressure inside the container?
to solve the equation use: Pv=nRt
p=?
v= 50. L
n=45
R=0.08206
t= 200 degrees C (must change to K so, 273.15 + 200 = 473.15 K)
p=nrt/v
p= (45)(0.08206)(473.15) = 34.94= 35 ATM
50
Video:
http://www.youtube.com/watch?v=BxUS1K7xu30
*This video explains again what a gas is and then explains the ideal gas law, Boyle's Law, etc.
Assumptions of the gas laws:
Main Concepts
Boyle's :
1. Temperature is constant
2. Number of moles is constant
Charles's:
1. Pressure is held constant
2. Number of atoms/molecules stays constant
Combined:
number of moles is constant
Ideal:
gas is ideal
Avogradro's:
perfect ideal gas
Pressures:
Main Concepts:
*Atm: standart atmosphere pressure
*atmospheric pressure is measured by the barometer
*conversions:
- 1 atm = 760 torr
- 1 atm = 760 mm Hg
- 1 atm = 14.7 psi (pounds per square inch)
- 1 atm = 101,325 Pa (pascal): SI unit for pressure
Calculations:
1) If the pressure of a sample is 934509 Pa, what is the pressure in atm?
1atm= 101,325 Pa
934509 Pa x 1 atm = 9.22289 atm
101,352 Pa
*the Pa will divide out leaving you with atm and then you plug it in to your calculator to find the answer in atm.
2) What is the pressure of the gas tank in torr, if the pressure was 1, 532 mm Hg?
1532 mm Hg x 1 atm x 760 torr = 1532 torr
760 mm Hg 1 atm
*the mm Hg and the atm divide out leaving you left with torr and the ability to plug it in and get your answer.
Activity:
http://quizlet.com/21917939/chemistry-gas-conversions-and-constants-flash-cards/
*This quizlet helps to identify each gas conversion with the correct number that goes along with the conversion factor.
Video:
http://www.youtube.com/watch?v=CX0__XRqrcg
*This video goes over STP which will be discussed further down as well as the conversions with pressure
Absolute Zero:
Main Concepts:
* Absolute zero is the bottom temperature where it can no longer get any colder. This is seen when volume decreases and temperature decreases as well. Because of absolute zero, an object can never have negative or zero volume. It is impossible.
Website:
http://www.colorado.edu/physics/2000/bec/temperature.html
*This is a fun, helpful website to help you better understand the concept of absolute zero.
Video:
http://www.youtube.com/watch?v=JHXxPnmyDbk
*This video again re-enforces the concept of absolute zero and why it is such a thing.
Dalton's Law of Partial Pressure:
Main Concepts:
*the relationship between the partial and total pressure of gas mixture in calculations
*Studies have shown that each component of a gas mixture behaves independently
*John Dalton was one of the first scientist to study it
*The partial pressure of a gas is the pressure that the gas would exert if it were alone in the container
*The total pressure is the total of all the pressures present in the container
*Ptotal = P1 + P2 + P3
Calculation:
Ptotal = P1 + P2 + P3
1) A sample of Oxygen gas is saturated with water vapor at 27 degrees C. The total pressure of the mixture was 772 torr and the water vapor pressure is 267 at 27 degrees C. What is the partial pressure of the Oxygen gas?
Ptotal= P1 + P2 ......... Ptotal - P1 = P2
772 torr - 267 torr = P2
P2= 505 torr
Activity:
http://quizlet.com/5876954/ap-ii-quiz-4-flash-cards/
*This is an activity about the partial pressure law by Dalton.
Video:
http://www.youtube.com/watch?v=RqffPYOoxd8
*This video explains how to apply Dalton's Law of Partia Pressure
The Kinetic Molecular Theory of Gases:
Main Concept:
*understand the term temperature
*qualitative relationships between the KM theory and the properties of gases
*the temperature of a gas reflects how rapidly, on average, its individual gas particles are moving
*At high temps the particles move very fast and hit the walls of the container frequently
* At low temps the particles motion is more sluggish and they collide with the walls of the container much less often
*temperature is a measure of the motion of the gas particles
*pressure is due to the collision with the walls of the container so therefor as the temperature increases the pressure will increase
Website:
http://www.chm.davidson.edu/vce/kineticmoleculartheory/basicconcepts.html
*This website explains the postulates and behave of gases that are present in this law.
Video:
http://www.youtube.com/watch?v=8jelON52wMw
*This video explains the Kinetic Molecular Theory of Gases with a model and labels it and show what happens to make this law true
Gas Stoichiometry and STP:
Main Concept:
*understand the molar volume of an ideal gas
*molar volume= 22.4 L
*always deals with stoichiometry problems involving gases
* this is so because it is under certain conditions that make it at STP.
*definition of STP
*standard temperature pressure
*0 degrees C and 1 atm
*properties of gases are usually given under these conditions
*molar volume of ideal gas at STP is 22.4 L
*Ideal Gas equation
*pv=nrt
Website:
http://www.chemtutor.com/gases.htm
*This website covers the gas law stoichiometry along with the other laws that were previously discussed within the chapter.
Activity:
http://quizlet.com/1656417/gas-laws-stoichiometry-flash-cards/
*This quizlet helps to identify STP and the stoichiometry process.
http://www.allbookez.com/ideal-gas-law-and-stoichiometry-answer-key/
*This website has a bunch of gas law stoichiometry worksheets to practice with along with answers so you can see if you are completing them right.
Video:
http://www.youtube.com/watch?v=XrrKXzghxAQ
*This video discusses how to solve gas law stoichiometry with problems not at STP.
http://www.youtube.com/watch?v=08TkB_eBQS8
*This video highlights gases that are at STP during stoichiometry.
Calculations: