Gas Laws

1. Gas Laws • Boyle’s Law • Charle’s law • Gay-Lussac’s Law • Avogadro’s Law • Dalton’s Law • Henry’s Law

2. What is Pressure? • Gas molecules cause pressure

3. The pressure of the gas in the container on the right would be ______ the pressure of the gas in the container on the left. • higher than • lower than • the same as

4. The pressure of the gas in the container on the right would be ______ as the pressure of the gas in the container on the left. • higher • lower • the same as Less particles will hit the sides of the container less often, causing less pressure.

5. The pressure of the gas in the container on the right would be ______ the pressure of the gas in the container on the left. • higher than • lower than • the same as

6. The pressure of the gas in the container on the right would be ______ as the pressure of the gas in the container on the left. • higher • lower • the same As counterintuitive as this may be, the size and mass of the gas particles do not affect the pressure, only the number of moles of particles affect the pressure. (more on this later….)

7. The pressure of the gas in the container on the right would be ______ the pressure of the gas in the container on the left. • higher than • lower than • the same as 10ºC 50ºC

8. The pressure of the gas in the container on the right would be ______ as the pressure of the gas in the container on the left. • higher • lower • the same as Particles moving faster will hit the sides of the container more often, AND hit with more force causing greater pressure. 10ºC 50ºC

9. Air Pressure • Air molecules cause air pressure • The weight of all the air on top of us causes the pressure. • Since air is a fluid, it pushes “all around,” not just from the top. • you will study fluid dynamics when you go to physics 1&2

10. BarometerMeasuring Air Pressure • Standard air pressure • 760 mm of Hg • 760 torr • 29.92 inches of Hg • 1 atm • 101.3 kPa

11. Manometermeasuring pressure in a closed container • Open-end and closed-end height height

12. A B C D Volume Volume Volume Volume moles moles moles moles Which graph below best represent the relationship between moles of gas (n) and volume (V) of container? (holding pressure and temperature constant.)

13. A B C D Volume Volume Volume Volume moles moles moles moles Which graph below best represent the relationship between moles of gas and volume of container? (holding pressure and temperature constant.)

14. number of molecules and volume • moles and volume • n & V • increase the number of moles, (while pressure & temp remain constant) and the volume will increase. • This is a direct relationship • n is proportional to V k = a constant

15. ? A B C There is gas in the flask, and more gas is added with the syringe. What would the pressure gauge read in the second picture? 5 5 8 2

16. ? A B C There is gas in the flask, and more gas is added with the syringe. What would the pressure gauge read in the second picture? 5 5 8 2

17. number of molecules and pressure • moles and pressure • n & P • increase the number of moles (while maintaining constant volume and temp) and the pressure increases. • this is a direct relationship • n is proportional to P k = a constant

18. The height of the piston in the container on the right would be ______ the height of the gas in the container on the left. ?? • higher than • lower than • the same as

19. The height of the piston in the container on the right would be ______ the height of the gas in the container on the left. • higher than • lower than • the same as

20. temperature and volume • T & V • increase the temperature (while pressure remains constant) and the volume increases. • this is a direct relationship • V is proportional to T k = a constant

21. The pressure of the gas in the container on the right would be ______ the pressure of the gas in the container on the left. (Temperature and moles remain constant.) ?? • higher than • lower than • the same as

22. The pressure of the gas in the container on the right would be ______ as the pressure of the gas in the container on the left. • higher • lower • the same as

23. pressure and volume • P & V • increase the volume (while temp and number of moles remains constant) and the pressure decreases. • this is an inverse relationship • P is inversely proportional to V k = a constant

24. The pressure of the gas in the container on the right would be ______ the pressure of the gas in the container on the left. (volume and moles remain constant) • higher than • lower than • the same as

25. The pressure of the gas in the container on the right would be ______ as the pressure of the gas in the container on the left. • higher • lower • the same

26. atm pressure and temperature • P & T • increase the temperature (while volume and moles remains constant) and the pressure increases. • this is an direct relationship • P is directly proportional to T k = a constant

27. P P V V V P = = k k = = = k k k n T n T Gas Relationships Together • All the k’s are different • Squish the k’s all together, let’s call kcombined, R • and since R = R • The Combined Gas Law

28. P1 V1 n1 T1 P1 V1 n1 T1 P2 V2 n2 T2 P2 V2 n2T2 = = The Combined Gas LawThe “Before and After” Gas Law • Consider 0.5 L of gas in sealed syringe in a 50ºC water bath with a pressure of 200 mmHg. The syringe is compressed to 0.1 L held at 50ºC, what will be the new pressure? • 2 L of oxygen gas in a sealed, rigid metal cylinder is at 0.80 atm at 25ºC. To what temperature, in Celsius should the gas be changed to reduce the pressure to 0.20 atm?

29. P1 V1 n1 T1 P1 V1 n1 T1 P2 V2 n2 T2 P2 V2 n2T2 = = The Combined Gas LawThe “Before and After” Gas Law • Consider 0.5 L of gas in sealed syringe in a 50ºC water bath with a pressure of 200 mmHg. The syringe is compressed to 0.1 L held at 50ºC, what will be the new pressure? • 2 L of oxygen gas in a sealed, rigid metal cylinder is at 0.80 atm at 25ºC. To what temperature, in Celsius should the gas be changed to reduce the pressure to 0.20 atm?

30. 1 atm pressure and temperature...again • Double the temp, does not double the pressure as you might expect. • The pressure only reaches 1.2 atm, why? ≠ 2 atm = 1.2 atm

31. We could graph the following data • Quickly sketch a graph of the following pressure and temp data collected for a tank of helium. • For reasons that might not make sense yet, set the range of your x-axis from -300ºC to 100ºC • hold the paper landscape • make the graph as large as is reasonable

32. Cool Down....Slow Down • As gases cool, they slow down and cause less pressure. • ...Slow molecules more = less pressure • ...slower still = even less pressure... • ...finally the molecules stop, and don’t cause any pressure and can’t go any slower. • this is as slow as the molecules can go, thus this is the coldest the molecules can get.

33. Kelvin the Absolute Temp Scale • Absolute zero, 0 = -273ºC • 0 K = -273ºC ºC + 273 = K -273ºC = 0 K

34. 1 atm ≠ 2 atm pressure and temperature...again • Double the temp, does not double the pressure as you might expect. • 50ºC = 323 K, and to double the pressure we must double the Kelvin temp to 646 K = 373ºC

35. The outside barometer reads 760 mmHg 380 mm 380 mm P = 0.5 atm P = 1.5 atm Manometers − measuring gas • Closed-end • harder to build, but easier to use • Open-end • easy to build (set up), but require a barometer reading and an addition or subtraction to determine the pressure in the gas tank

36. Pre LAD D.1Gas in a Tube

37. Predict:As you lift the eudiometer up in the cylinder, the vol of the gas in the eudiometer will measure ? 1 2 • larger in 1 • larger in 2 • the same volume

38. As you lift the eudiometer up in the cylinder, the vol of the gas in the eudiometer is larger in 1 2 • The “weight” of the volume of water above the gas in the eudiometer will “squish” the gas into a smaller volume. • Thus the volume will be larger in #2

39. As you lift the eudiometer up in the cylinder, the pressure of the gas in the eudiometer will ? • stay the same • get smaller • get larger

40. As you lift the eudiometer up in the cylinder, the pressure of the gas in the eudiometer will • stay the same • get smaller • Since we just learned that the Volume gets larger, the pressure must get smaller • Or...consider the setup as a manometer, and the gas is “winning” (higher pressure than air) on the left, and the gas on the right is “losing” (lower pressure than air). • get larger

41. In the eudiometer pictured, the pressure of the air inside • is the same as the air pressure • is more than air pressure • is less than the air pressure

42. In the eudiometer pictured, the pressure of the air inside • is the same as the air pressure • is more than air pressure • is less than the air pressure • The pressure in the eudiometer is the same as the air pressure, however, two gases are causing the equal pressure - gas and water vapor, thus the gas must be less than the outside air pressure.

43. Exactly what is in the gas space of the eudiometer? • just the gas that I put in with the hose as demonstrated • the gas that I put in and some other gas as well

44. Dalton’s Law ofPartial Pressures

45. The red gas is 2.0 atm, the blue gas is 2.0 atm, when combined together in one of the containers, the pressure would be • 4.0 atm • less than 4.0 atm • more than 4.0 atm • 2.0 atm • no way of knowing because it depends on the molar mass of each of the gases. • no way of knowing because maybe the gases react together

46. The red gas is 20 atm, the blue gas is 20 atm, when combined together in one of the containers, the pressure would be • 4.0 atm • Dalton’s Law of Partial Pressures • Ptotal = P1 + P2 + P3 + .... • For ideal gases, their identity does not matter • less than 4.0 atm • more than 4.0 atm • 2.0 atm • no way of knowing because it depends on the molar mass of each of the gases.

47. A rigid flask contains 0.3 moles He, 0.4 moles H2, and 0.5 moles Ne. The total pressure is 15 atm. What is the partial pressure of the H2? (No calculator.) • Input a numeric answer. • or work together and discuss with your nearby mates 47

48. A rigid flask contains 0.3 moles He, 0.4 moles H2, and 0.5 moles Ne. The total pressure is 15 atm. What is the partial pressure of the H2? (No calculator.) • the mole fraction: • (a percentage without multiplying by 100) • Let’s look for this on the formula sheet….

49. 500 mL 1 atm 1L 1 atm If the inert gas from the two blue containers were put into the empty gold container. What would be the total pressure? • 1 atm • 1.5 atm • 2 atm • 2.5 atm • 3 atm • 4 atm • unable to be determined 1L

50. 500 mL 1 atm 1L 1atm 1L If the gas from the two blue containers were put into the empty gold container. What would be the total pressure? • 1 atm • 1.5 atm, assuming temp and remained constant. • the large blue container would be 1atm in same size container • the small blue container, PV = PV thus double vol = half pressure = 0.5 atm • sum for the total = 1.5 atm