1. Gas Laws

2. Variables influencing gases
Pressure (P)
Three units (mm Hg, atm, kPa)
Volume (V)
Units (L or mL)
Temperature (T)
Units (K)
Moles (n)
mol = n

3. Pressure Conversion 760 mm Hg = 1 atm = 101.3kPa
Also called standard pressure
Example: The atmospheric pressure in MI is around 750mm Hg. Determine the pressure in atmospheres and kPa.
750 mm Hg = atm = 100 kPa

4. Temperature Conversion
°C = Kelvin
Standard temperature is at 273 K
Example: If the temperature is 47°C, what is the temperature in Kelvin?
47°C = 320K

5. Boyle’s Law
Robert Boyle described the relationship between pressure (P) and volume (V) of a gas.
As V ↓, P ↑. As V ↑, P ↓.
This is an inversely proportional relationship. When one variable goes up, the other goes down.

7. Boyle’s Law
P1V1 = P2V2
Boyle Visual

8. Boyle’s Law - Example
The gas in a balloon has a volume of 7.5L at 100kPa. The balloon is released into the atmosphere, and the gas expands to a volume of 11L. Assuming temperature is constant, what is the new pressure?
Answer: 68 kPa

9. Charles’ Law
Jacques Charles observed the relationship between volume (V) and temperature (T).
As T ↑, V also ↑. As T ↓, V ↓.
This is a directly proportional relationship. When one variable goes up, the other goes up too.

10. Charles’s Law

11. Charles’s Law
V1/T1 = V2/T2
Charles Visual

12. Charles’s Law - Example
A gas sample occupies 2.5L at 300.0K. What volume will the gas occupy at 80.0K?
Answer: 0.67L

13. Guy-Lussac’s Law
Joseph Guy-Lussac studied the relationship between pressure (P) and temperature (T).
As T ↑, P also ↑. As T ↓, so did P.
This is a directly proportional relationship. As one variable goes one way, so does the other.

14. Guy-Lussac’s Law
P1/T1 = P2/T2

15. Guy-Lussac’s Law - Example
A gas has a pressure of 6.58kPa at 539K. If the temperature is decreased to 211K at a constant volume, what will the resulting pressure be?
Answer: 2.58 kPa

16. Sources http://www.nasa.gov/images/content/122625main_k_sun2.jpg

17. Combined Gas Law
Putting them together

18. Combined Gas Law
Often volume, temperature, and pressure all change at the same time.
Deals with a fixed amount of gas.
T represents temperature in Kelvin
Units must match on both sides

19. Example
A gas at 155 kPa and 25°C occupies a container with initial volume of 1.00 L. By changing the volume, the pressure of the gas increases to 605 kPa and the temperature is raised to 125°C. What is the new volume?
Answer: L

20. STP Standard pressure is at 1atm Standard temperature is 273 K
STP stands for standard temperature and pressure.

21. Sources

24. Partial Pressures

25. Dalton’s Law of Partial Pressures
The total pressure of a gas mixture is the sum of the partial pressures of the component gases.
Ptotal = P1+P2+P3+P4+…

26. Example
A gas mixture containing oxygen, nitrogen, and carbon dioxide has a total pressure of 32.9 kPa. If PO2=6.6 kPa and PN2=23.0 kPa, what is PCO2?
Answer: 3.3 kPa

27. Sources http://www.kinneybrothers.com/FLASH%20CARDS/confused.jpg

28. Ideal Gas Law
The Culmination

29. R
R is the ideal gas constant
Its value depends on the units used for pressure.
If P is in atm:

30. Ideal Gas Law
PV=nRT

31. Example
You fill a rigid steel container (volume = 20.0 L) with nitrogen gas to a final pressure of 2.00 * 104 kPa at 28°C. How many moles of nitrogen gas does the cylinder contain?
Answer: 1.60 * 102 mol N2(g)

32. Example – Round Two
What pressure will be exerted by mol of a gas at 25°C if it is contained in a L vessel?
Answer: 16.9atm

33. Ideal Gas Law Practice 

34. There are 8g H2 gas in a balloon
There are 8g H2 gas in a balloon. What is the volume at 25°C and 758mmHg?

35. If the total air pressure is 0.99atm, the partial pressure of CO2 is 0.05atm, and the partial pressure of hydrogen sulfide is 0.02atm, what is the partial pressure of the remaining air?

36. 30g of a gas occupy a volume of 82. 0mL at 3. 00atm and 27°C
0.30g of a gas occupy a volume of 82.0mL at 3.00atm and 27°C. Calculate the molar mass of the gas.

37. 2H2(g) + O2(g)  2H2O(g)
How many liters of water can be made from 55g of O2(g) at 12.4atm and 85°C?

38. At what pressure would 0.150mol N2(g) at 23.0°C occupy 8.90L?

39. How many grams of carbon dioxide gas are present in a closed 3
How many grams of carbon dioxide gas are present in a closed 3.0L container if the gas is exerting a pressure of kPa at 28°C?

40. Graham’s Law of Effusion

41. Diffusion
Movement of particles from areas of higher concentration to lower concentration

42. Kinetic Energy
The average kinetic energy of molecules in a gas depends only on temperature.
KE = 1/2mv2
The velocity of the gas depends on its mass.

43. Effusion
The process where molecules of a gas in a container randomly pass through a hole in the container.

44. Graham’s Law Equation

45. Larger GFM = slower rate of effusion.
Graham’s Law
Larger GFM = slower rate of effusion.

46. Answer: CO2 effuses 0.9X as fast as HCl.
Example
Compare the rate of effusion of carbon dioxide with that of hydrogen chloride at the same temperature and pressure.
Answer: CO2 effuses 0.9X as fast as HCl.

47. Example - Again
If a molecule of neon gas travels at an average of 400m/s at a given temp., estimate the average speed of a molecule of butane gas, C4H10, at the same temp.
Answer: 235m/s

48. Sources http://www.coletechnologies.us/files/effusion_box.JPG