1. Gas Laws
Chapters

2. Review Temperature Pressure Volume Average kinetic energy
Collisions of gas particles between each other and container walls
Volume
Amount of space

3. Ideal Gas
Don’t exist
Model to explain behavior of all gases

4. Kinetic Molecular Theory
The particles in a gas are constantly moving in rapid, random, straight-line motion.
Gas particles have no volume compared to the volume of the gas.
No attraction between particles
All collisions are completely elastic

5. Gas Laws Boyle’s Law Charles’s Law Amontons’s Law Combined Gas Law
Avogadro’s Law
Dalton’s Law of Partial Pressures
Ideal Gas Law

6. Boyle’s Law Relationship between pressure and volume
Constant Temperature
Mathematical relationships
As pressure is increasing, volume is decreasing
As pressure is decreasing, volume is increasing

7. Boyle’s Law V P

8. Boyle’s Law
PV = constant
Temperature remains constant

9. Example
A 40 L sample of gas at 1atm of pressure is compressed to 10 L. What is the new pressure of the gas?
P1V1 = P2V2
(1atm)*(40L) = P2*(10L)
P2 = 4 atm

10. Example
The pressure of a 25 L sample is changed from 2 atm to 0.4 atm. What is the new volume of the gas?
P1V1 = P2V2
(2atm)*(25L) = (0.4atm)*V2
V2 = 125 L

11. Real Life

13. Charles’s Law Relationship between volume and temperature
Constant Pressure
Mathematical relationships
As temperature is increasing, volume is increasing
As temperature is decreasing, volume is decreasing

14. Charles’s Law T V

15. Charles’s Law V/T = constant Temperature must be in Kelvin
Pressure remains constant
Temperature must be in Kelvin

16. Example
A 4L sample of gas at 300K is heated to 600K. What is the new volume?

17. Example
A gas occupying 45L at 27°C is cooled until its volume is 15L. What is the new temperature of the gas?

19. Amontons's Law
In the winter the tire sensors on my wife’s car beep, indicating that there is low pressure in the tires. Why?
What factor is changing with the weather?
What factor is responding to this change?
Which factor(s) remain constant?

20. Amontons's Law Mathematical relationships
As temperature increases, pressure increases
As temperature decreases, pressure decreases

21. Amontons's Law T P

22. Amontons's Law P/T = constant Temperature must be in Kelvin
Volume remains constant (rigid container)
Temperature must be in Kelvin

23. Example
In a pressure cooker, a sample of gas at 1 atm and 300K is heated to 400K. What is the pressure at this temperature?

24. Example
A sample of gas at kPa and 27°C is heated until its pressure is 3.5atm. What is the new temperature?

26. Combined Gas Law
Goal
Understands how to use the gas laws to predict the behavior of gases.
Pressure vs. volume (Boyle)
Volume vs. temperature (Charles)
Volume, temperature, and pressure (Combined)

27. Review
Boyle’s Law
Charles’s Law
Amontons's Law

28. Question
How often do only 2 properties of a gas change while the other remains constant?
Rarely
Need a gas law that incorporates all three properties (PTV) changing

29. Combined Gas Law
Combines Boyle’s, Charles’s, and Amontons's Laws together

30. Example

31. Example

32. Worksheet

33. Combined Gas Law
Goal
Understands how to use the gas laws to predict the behavior of gases.
Pressure vs. volume (Boyle)
Volume vs. temperature (Charles)
Volume, temperature, and pressure (Combined)

35. Review
1 mole of ANY gas occupies 22.4L of volume at STP

36. Avogadro’s Law
Relationship between the amount of gas and the volume of the gas
Mathematical relationships
As the amount of gas increases, volume increases
As the amount of gas decreases, volume decreases

37. Avogadro’s Law n V

38. Avogadro’s Law V/n = constant
Pressure and Temperature remains constant

39. Avogadro’s Law
Equal volumes of gas at the same Temperature and Pressure have the same number of particles
At the same temperature and pressure, which sample contains the same number of moles of particles as 1 liter of O2(g)?
A. 1 L Ne(g) B. 0.5 L SO2(g)
C. 2 L N2(g) D. 4 L H2O(g)

41. Dalton’s Law Demonstration
Assume each jelly bean represents 1 mole of gas
How many moles are in the flask?
What fraction is green?
Does color make a difference in pressure when shaken?

42. Dalton’s Law Mole Fraction (XA) Partial Pressure (PA)
Moles of one gas divided by total moles of gas
Partial Pressure (PA)
Pressure exerted by one gas in a sample of gas

43. Dalton’s Law of Partial Pressures
How does partial pressure relate to total pressure?
Sum of partial pressures equals total pressure
PT = PA + PB + PC…

44. Dalton’s Law of Partial Pressures
How can we relate mole fraction to partial pressure and total pressure?

45. Example
A container has 1 mol of hydrogen, 1 mol of nitrogen, and 1 mol of oxygen. What is the mole fraction of hydrogen?
Moles of Hydrogen
Total Moles

46. Example
A container has 1 mol of hydrogen, 1 mol of nitrogen, and 1 mol of oxygen. If the total pressure is 6 atm, what is the partial pressure of nitrogen?
Moles of Nitrogen
Total Moles

48. Review
Boyle’s Law
Charles’s Law
Amontons's Law
Avogadro’s Law

49. All Together Now Constant
If we add Avogadro’s Law into the Combined Gas Law:
Constant

50. Ideal Gas Law
PV = nRT
R = Universal Gas Constant
Ideal Gases follow assumptions of the Kinetic Molecular Theory

51. Kinetic Theory of Gases
The particles in a gas are constantly moving in rapid, random, straight-line motion.
Gas particles have no volume compared to the volume of the gas.
No attraction between particles
All collisions are completely elastic

52. Ideal Gases When do real gases act most like an ideal gas?
High Temperature
Low Pressure
When do real gases act least like an ideal gas?
Low Temperature
High Pressure

53. Gas Laws Boyle’s Law Charles’s Law Amontons's Law Combined Gas Law
Avogadro’s Law
Dalton’s Law of Partial Pressures
Ideal Gas Law