1. Gases

2. Gases – Intro Video

3. Kinetic Theory
states that particles in all forms of matter are in continuous motion

4. Kinetic Theory
Kinetic energy
= energy of motion

5. Kinetic Theory
Basic Assumptions:
1. Gases consist of large numbers of tiny particles that are far apart relative to their size

6. Kinetic Theory
2. The particles of a gas move rapidly and are in constant random motion.

7. Kinetic Theory
3. All collisions are elastic (kinetic energy is constant)

8. Kinetic Theory
4. There are no forces of attraction or repulsion between gas particles

9. Kinetic Theory
5. The average kinetic energy of a gas particle depends on temperature of
a gas

10. Gas Pressure
the force exerted by a gas per unit surface area of an object
Results from collision of gas particles

11. Vacuum
Empty Space with no particles and no pressure

12. Atmospheric Pressure
results from collisions of air molecules

13. Atmospheric Pressure
measured by a barometer

14. Standard Atmosphere Pressure Conversions
1 atm = 760mm Hg = 101.3kPa = 760 Torr
The atmospheric pressure is 2.50 atm. Convert this to kPa.

15. STP
Standard Temperature and Pressure

16. Kinetic E and Kelvin T
when an object is heated, KE is increased, which results in an increase in T

17. Kinetic E and Kelvin T
Particles at absolute zero (0 Kelvin) have no kinetic energy

18. Kinetic E and Kelvin T
average KE is directly proportional to Kelvin T
Kelvin = oC + 273

19. How can you alter Pressure?
Describe 3 ways to alter the P in the container below
Use the KMT to explain

20. 3 ways to alter gas pressure
1. Change the size of the container
2. Alter the temperature
3.Adding or removing particles

21. Gas Laws
Boyle’s Law states that for
a given mass at constant T, the volume of a gas varies inversely with pressure

22. Gas Laws

23. Gas Laws

24. Gas Laws
A high altitude balloon contains 30.0L of He at 103 kPa. What is the volume when the balloon rises
where the pressure is 25.0kPa?

25. Gas Laws
Charles’ Law states that volume of a fixed mass of gas is directly proportional
to its Kelvin temperature if the pressure is constant.

26. Gas Laws

27. Gas Laws

28. Gas Laws
A balloon is inflated in a room at 24oC and has a volume of 4.00L. What is the new volume if the temperature rises to 58oC at constant pressure?

29. Gas Laws
Gay-Lussac’s Law states that the pressure of a gas is directly proportional to the Kelvin temperature if the volume remains constant

30. Gas Laws

31. Gas Laws
The gas left in a used aerosol can is at 103 kPa at 25oC. If this can is thrown into a fire, what is the pressure at 928oC?

32. Gas Laws
Combined Gas Law

33. Gas Laws
The volume of a gas filled balloon is 30.0L at 40.0oC and 153 kPa. What volume would the balloon have at STP?

34. Ideal Gas and Kinetic Theory
a truly ideal gas conforms
to gas laws at all conditions and conforms to kinetic theory

35. Ideal Gas and Kinetic Theory
Real gases do have volume and forces of attraction

36. Ideal Gas and Kinetic Theory
At high temperature and low pressures, real gases behave like ideal gases
In our problems we assume we have ideal gases

37. Ideal Gas Law
the number of moles of a gas are directly related to the number of particles in a gas, and directly proportional to the volume of a gas (proposed by Clapeyron)

38. Ideal Gas Law

39. Ideal Gas Law
A rigid steel cylinder has a volume of 20.0L of N2 and 2.00 x 104 kPa at 28oC. How many moles of N2 are in the container?

40. Ideal Gas Law
A deep underground cavern contains 2.24 x 106 L of CH4(g) at 1.50x103kPa at 42oC. How many kilograms of gas are deposited?

41. Ideal Gas Law
Challenge:
At 28oC and atm, 1.00L of gas has a mass of 5.16g. What is the molar mass of the gas?

42. Ideal Gas Law
Challenge:
What is the density of a sample of NH3 if the pressure is atm and temperature is 63oC?

43. Ideal Gas Law
Challenge:
What is the density of a Argon gas at a pressure of 551 Torr and is 25oC?

44. Avogadro’s Hypothesis
states equal volumes of gases at the same T and P contain equal numbers of particles
22.4L = 1 mol at STP

45. Avogadro’s Hypothesis

46. Avogadro’s Hypothesis
Determine the volume occupied by mole H2 gas at STP.

47. Avogadro’s Hypothesis
Determine the volume occupied by 14.0g nitrogen gas at STP.

48. Dalton’s Law of Partial Pressure
At constant T and V, the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of each component gas
Ptotal = P1 + P2 + P3 ….

49. Dalton’s Law of Partial Pressure

50. Dalton’s Law of Partial Pressure

51. Graham’s Law of Effusion
Diffusion = gradual mixing
of 2 gases due to their spontaneous, random motion

52. Graham’s Law of Effusion
Effusion = molecules of a gas confined in a container randomly pass through a tiny opening in the container

53. Graham’s Law of Effusion
lighter molecules move faster than heavier molecules at the same T

54. Graham’s Law of Effusion
states that rates of effusion of gases at the same T and P are inversely proportional to the square roots of their molar mass

55. Graham’s Law of Effusion