1. The Gaseous State
Chapter 10

2. Objectives
Understand the definition of pressure. Use the definition to predict and measure pressure experimentally
Describe experiments that show relationships between pressure, temperature, volume, and moles of a gas sample
Use empirical gas laws to predict how change in one of the properties of a gas will affect the remaining properties.
Use empirical gas laws to estimate gas densities and molecular masses.
Use volume-to-mole relationships obtained using the empirical gas laws to solve stoichiometry problems involving gases.

3. Objectives
6. Understand the concept of partial pressure in mixtures of gases.
7. Use the ideal kinetic-molecular model to explain the empirical gas laws.
8. List deficiencies in the ideal gas mode3el that will cause real gases to deviate from behaviors predicted by the empirical gas laws. Explain how the model can be modified to account for these deficiencies.

5. Definition of Gas
Gas: large collection of particles moving at random throughout a volume that is primarily empty space. Have relatively large amount of energy.
Gas pressure: due to collisions of randomly moving particles with the walls of the container.
Force/unit area

6. Definition of Gases STP: 0°C, and 1 atmosphere pressure
Elements that exist as gases at STP: hydrogen, nitrogen, oxygen, fluorine, chlorine and Noble Gases
Ionic compounds are all solids
Molecular compounds - depends on the intermolecular forces. Most are liquids and solids. Some are gaseous

7. Properties of Gases Assume the volume and shape of their container
Compressible
Mix evenly and completely when confined to the same container
Lower densities than liquids and solids
Allotropes: O2 ↔O3

8. Kinetic Molecular Theory of Gases
Tiny particles in continuous motion ( the hotter the gas, the faster the molecules are moving) with negligible volume compared to volume of container.
Molecules are far apart from each other
Do not attract or repel each other (?).
All collisions are elastic (gas does not lose energy when left alone).
The energy is proportional to Kelvin temperature. At a given temperature all gases have the same average KE.

9. Properties of Gases Observation Hypothesis Gases are easy to expand
Gases are easy to compress
Gases have densities that are 1/1000 of solid or liquid densities
Gases completely fill their containers
Hot gases leak through holes faster than cold gases

10. Properties of Gases Observation Hypothesis Gases are easy to expand
Gas molecules do not strongly attract each other
Gases are easy to compress
Gas molecules don’t strongly repel each other
Gases have densities that are 1/1000 of solid or liquid densities
Molecules are much farther apart in gases than in liquids and solids
Hot gases leak through holes faster than cold gases
Gas molecules are in constant motion

11. Atmospheric Pressure
Intensive or Extensive Property?

12. Pressure
Pressure is due to collisions between gas molecules and the walls of the container. Magnitude determined by: force of collisions and frequency.
Pressure: force per unit area: P =F/A
Standard temperature: 0ºC = K
Standard pressure: 1 atm in US; 1 bar elsewhere

13. Pressure Unit Symbol Conversions Pascal Pa 1 Pa = 1 N/m2 Psi lb/in2
Atmosphere
Atm
1 atm = Pa = 14.7 lb/in2
Bar
1 bar = Pa
Torr
760 torr = 1 atm
Millimeter mercury
mm Hg
1 mm Hg = 1 torr

14. Pressure: Examples
How much pressure does an elephant with a mass of 2000 kg and total footprint area of 5000 cm2 exert on the ground?
Estimate the total footprint area of a tyrannosaur weighing kg. Assume it exerts the same pressure on its feet that the elephant does.

15. Pressure Measuring pressure: Strategy:
Relate pressure to fluid column heights
You can’t draw water higher than 34 feet by suction alone. Why?
Hypothesis: atmospheric pressure supports the fluid column
Develop the equation

16. Measuring Pressure

17. Pressure: Barometer
Barometer measures atmospheric pressure as a mercury column height.

18. Pressure: Open-Manometer
Manometer measures gas pressure as a difference in mercury column heights.
Two types: closed manometer
open manometer

19. Measuring Gas Pressure
Closed-manometer : the arm not connected to the gas sample is closed to the atmosphere and is under vacuum.
Explain how you can read the gas pressure in the bulb.

20. Pressure: Examples
3. Calculate the difference in pressure between the top and the bottom of a vessel exactly 76 cm deep filled at 25 ºC with a) water; b) mercury (d = 13.6 g/cm3)
(7.43 x 103 Pa;100.9 x 103 Pa)
4. How high a column of air would be necessary to cause the barometer to read 76 cm of mercury, if the atmosphere were of uniform density 1.2 kg/m3?
dHg = kg/m3 (8.6 km)
5. A Canadian weather report gives the atmospheric pressure as kPa. What is the pressure in atmospheres? Torr? Mm Hg?

21. The Gas Laws: State of Gas
Property
Symbol
Unit
Property Type
Pressure P
atm, torr, Pa
Intensive
Volume V
L, cm3
Extensive
Temperature T K
Moles n
mol
extensive

22. The Gas Laws: State of Gas
Any equation that relates P, V, T, and n for a material is called an equation of state.
Experiment shows PV = nRT is an approximate equation of state for gases.
R is the gas law constant
Determined by measuring P, V, T, n and computing R = PV/nT
Value depends on units chosen for P, V, T
Notice: 1 Joule = 1 N m = 1(Pa) (m3)

23. The Gas Laws
Gas laws deal with the MACROSCOPIC view of gases and we try to explain the macroscopic properties by examining the microscopic behaviors (many molecule behaviors)

24. Prentice Hall Simulations of Gas Laws

25. Boyle’s Law: Experiment
Relate volume to pressure when everything else is constant. Experiment: trapped air bubble at 298 K
Volume, mL
Pressure, torr
PV )mL torr)
10.0
760.0
20.0
379.6
30.0
253.2
40.0
191.0
Graphs?

26. Boyle’s Law: Experiment
Relate volume to pressure when everything else is constant. Experiment: trapped air bubble at 298 K
Volume, mL
Pressure, torr
PV (mL torr)
10.0
760.0
7.60 x 103
20.0
379.6
7.59 x 103
30.0
253.2
40.0
191.0
7.64 x 103
Graphs?

27. Boyle’s Law: Volume/Pressure Relationship
At constant n, and T, the volume of a gas decreases proportionately as its pressure increases. If the pressure is doubled, the volume is halved.

28. Boyle’s Law: Volume/Pressure Relationship
What happens to the volume of the gas as the pressure increases? Mathematical Relationship?

29. Plot of Boyle’s Law
V versus P
V versus 1/P
Type of Graphs?

30. Boyle’s Law MOLECULAR VIEW
Boyle’s Law – the volume of a fixed amount of gas at constant temperature and constant number of moles is inversely proportional to the gas pressure.
MOLECULAR VIEW

31. Boyle’s Law MOLECULAR VIEW:
Boyle’s Law – the volume of a fixed amount of gas at constant temperature and constant number of moles is inversely proportional to the gas pressure.
MOLECULAR VIEW:
Confining molecules to a smaller space increases the number (frequency) of collisions, and so increases the pressure

32. Charles' Law (V/T Relationships)
Relate volume to temperature, everything else is constant. Experiment: He bubble trapped at 1 atm.
V, mL
T, ºC
T, (K)
V/T, mL/K
40.0
0.0
273.2
44.0
25.0
298.0
47.7
50.0
323.2
51.3
75.0
348.2
55.3
100.0
373.2
80.0
546.3

33. Charles' Law (V/T Relationships)
Relate volume to temperature, everything else is constant. Experiment: He bubble trapped at 1 atm.
V, mL
T, ºC
T, (K)
V/T, mL/K
40.0
0.0
273.2
0.146
44.0
25.0
298.0
0.148
47.7
50.0
323.2
51.3
75.0
348.2
0.147
55.3
100.0
373.2
80.0
546.3

34. Charles’ Law: Volume/Temperature Relationships
At constant n and P, the volume of a gas increases proportionately as its absolute temperature increases, If the absolute temperature doubles, the volume is doubled.
K = ºC

35. Charles’ Law
A plot of V versus T for a gas sample. What type of graph? Equation?

37. Charles' Law
Kinetic Interpretation of Charles's Law? Why higher pressure? Equation?
Frequency and force of collision…

38. Charles’ Law MOLECULAR VIEW
The volume of the gas is directly proportional to its Kelvin temperature, when everything else is constant.
MOLECULAR VIEW

39. Charles’ Law MOLECULAR VIEW
The volume of the gas is directly proportional to its Kelvin temperature, when everything else is constant.
MOLECULAR VIEW
Raising temperature increases the number of collisions and force of collisions (KE increases) with container wall. If the walls are flexible, they will be pushed back and the gas expands.

40. Charles’ Law
Assume that you have a sample of gas at 350 K in a sealed container, as represented in (a). Which of the drawings (b) – (d) represents the gas after the temperature is lowered from 350 K to 150 K

41. Gay Lussac’s Law Molecular View;
The pressure of the gas is directly proportional to its Kelvin temperature, when everything else is constant.
Molecular View;

42. Gay Lussac’s Law Molecular View;
The pressure of the gas is directly proportional to its Kelvin temperature, when everything else is constant.
Molecular View;
Raising the temperature increases the number of collisions and the kinetic energy of the molecules. More collisions with greater energy (force) means higher pressure.

43. Combined Gas laws

44. Avogadro’s Law: Relates n to Volume

45. Volume of Real Gases at STP

46. Avogadro’s Law: Relates n to Volume
At constant T and P, the volume of a gas is directly proportional to moles of gas. Molar volume is almost independent of the type of gas.
Samples of two gases with the same V, P, T contain the same number of molecules.
MOLECULAR VIEW

47. Avogadro’s Law: Relates n to Volume
At constant T and P, the volume of a gas is directly proportional to moles of gas. Molar volume is almost independent of the type of gas.
Samples of two gases with the same V, P, T contain the same number of molecules (moles).
MOLECULAR VIEW
Type of gas does not influence distance between molecules too much.

48. Avogadro’s Law: Example 6
Show the approximate level of the movable piston in drawings (a) and (b) after the indicated changes have been made to the initial gas sample.

49. Avogadro’s Law: Answer to Example 6

50. Example 7
Show the approximate level of the movable piston in drawings (a), (b), and (c ) after the indicated changes.

51. Gas Laws: Examples
8. A balloon indoors, where the temperature is 27.0 ºC, has a volume of 2.00 L. What will be its volume outdoors, where the temperature is ºC? (Assume no change in pressure)
[ 1.67 L]
9. A sample of nitrogen occupies a volume of 2.50 L at -120 ºC and 1.00 atm. Pressure. To which of the following approximate temperatures should the gas be heated in order to double its volume while maintaining a constant pressure?
-240 ºC ºC ºC ºC
[30.0 ºC]

52. Gas Laws: Examples
10. Calculate the volume occupied by 4.11 g of methane gas at STP.
[5.74 x 103L]
11. What is the mass of propane, C3H8, in a 50.0 L container of the gas at STP?

53. Ideal Gas Law
PV = nRT
Gas Constant R = (L atm)/(mol K)

54. Examples
12. Sulfur hexafluoride, SF6 is a colorless, odorless, very unreactive gas. Calculate the pressure (in atm) exerted by 1.82 moles of the gas in a steel container of volume 5.43 L at 69.5 ºC (9.42 atm)
13. Calculate the volume (in liters) occupied by 7.40 g of CO2 at STP ( 3.77 L)

55. Gas Laws: Examples
14. A gas initially at 4.0 L, 1.2 atm, and 66 º undergoes a change so that its final volume an temperature become 1.7 L and º C. What is its final pressure? Assume the number of moles remains unchanged.
15. A certain container holds 6.00 g of CO2 at ºC and 100. kPa pressure. How many grams of CO2 will it hold at 30.0 ºC and the same pressure?

56. Gas Laws Summary Changing variables Variables held constant
Relationship
Law
P, V
n, T
P1V1 = P2 =V2
Boyle’s Law
V, T
n, P
V/T = k
Charle’s Law
P, T
n, V
P/T = k
Gay-Lussac’s
V/n = k
Avogadro’s
P, V, T n
PV/T = k
Combined
P, V, T, n
none
PV/(nT) = R
Ideal Gas Law

57. Gas Density and Molar Mass
Purple M&M Do Red Too Or
Michael Mo do the right thing

58. Density and Molar Mass: Examples
16. Calculate the density of methane gas, CH4, in grams per liter, at 25 ºC and atm.
[0.641 g CH4/L]
17. Under what pressure must O2(g) be maintained at 25 ºC to have density of 1.50 g/L?
[1.15 atm]
18. The density of a gaseous organic compound is 3.38 g/L at 40.0 ºC and 1.97 atm. What is its molar mass?
[44.1 g/mol]
19. A gaseous compound is 78.14% boron, 21.86% hydrogen. At 27.0 º C, 74.3 mL of the gas exerted a pressure of 1.12 atm. If the mass of the gas was g, what is its molecular formula? [B2H6]

59. Stoichiometry Involving Gases
Use regular Stoichiometry techniques, except that
for non STP conditions, and 22.4 L/mole for STP
conditions.

60. Stoichiometry: The Law of Combining Volumes Involving Gases
When gases measured at the same temperature and pressure are allowed to react, the volumes of gaseous reactants and products are in small whole-number ratios.

61. Stoichiometry: The Law of Combining Volumes Involving Gases (Avogadro’s Explanation)
When the gases are measured at the same temperature and pressure, each of the identical flasks contains the same number of molecules.

62. Examples (Stoichiometry)
20. How many liters of O2(g) are consumed for every 10.0 L of CO2(g) produced in the combustion of liquid pentane, C5H12, if each gas is measured at STP?
[16.0 L O2]
21. Given the reaction
C6H12O6(s) + O2(g) → 6CO2(g) + 6H2O(g),
calculate the volume of CO2 produced at 37.0 ºC and 1.00 atm when 5.60 g of glucose is used up in the reaction [4.75 L]
22. A 2.14 L- sample of hydrogen chloride gas at 2.61 atm and 28.0 ºC is completely dissolved in 668 mL of water to form hydrochloric acid solution. Calculate the molarity of the acid solution [0.338M]

63. Dalton’s Law of Partial Pressure
Assume that you have a mixture of He (4 amu) and Xe ( 131 amu) at 300 K. Which of the drawings best represents the mixture (blue= He; green = Xe)?

64. Dalton’s Law of Partial Pressure
What is the partial pressure of each gas – red, yellow, and green – if the total pressure inside the following container is 600 mm Hg?
2. What is the volume of each gas inside the container, if the total volume of this vessel is 1.0 L?

65. Dalton’s Law of Partial Pressure

66. Dalton’s Law of Partial Pressures
Mole fraction: moles of component per mole of mixture
Avogadro’s Law: mole fraction = volume fraction for ideal gas
Examples:
2 L of He gas is mixed withy 3 L of Ne gas. What is the mole fraction of each component?
Air is approximately 79% N2 and 21 %O2 by mass. What is the mole fraction of O2 in the air?

67. Dalton’s Law of Partial Pressures
Partial Pressure – the pressure of an individual gas component in a mixture: PA
Examples:
One mole of air contains 0.79 moles of nitrogen and 0.21moles of oxygen. Compute the partial pressure of these gases at a total pressure of 1.0 atm atm and at a total pressure of 3.0 atm (about the pressure experienced by a diver under 66 ft of seawater).
What is the mole fraction of water in the headspace of a soda bottle, if the gas is at 2.0 atm and 25 ºC is torr?

68. Dalton’s Law of Partial Pressures
Ptotal = P1 + P2 + P3 +……. Pn
P1 = x1PT

69. Dalton’s Law of Partial Pressures
Dalton’s Law: The total pressure of a mixture of gases is just the sum of the pressures that each gas would exert if it were present alone.
MOLECULAR VIEW
Molecules of a gas do not attract or repel each other. The distances between particles are very large, therefore each particular gas occupies the entire container and adds its pressure to the total pressure in the container.

70. Dalton’s Law: Examples
23. A mixture containing mol He, mol of Ne, and mol of Ar is confined in a 7.00 L vessel at 25 ºC.
A) Calculate the partial pressure of each of the gasses in the mixture.
B) Calculate the total pressure of the mixture.
[P of He 1.88 atm; P of Ne 1.10 atm; P of Ar atm; P total 3.34 atm]
24. The partial pressure of nitrogen in air is 592 torr. Air pressure is 752 torr, what is the mole fraction of nitrogen?
[7.87 x 10-1]

71. Dalton’s Laws: Examples
25. What is the partial pressure of nitrogen if the container holding the air is compressed to 5.25 atm? [4.13 atm]
26. Ca(s) + H2O(l) →Ca(OH)2 + H2(g)
H2(g) was collected over water. The volume of gas at 30.0 ºC and P= 988 mm Hg is 641 mL. What is the mass (in grams) of the H2 gas obtained? The pressure of water at 30.0 ºC is mm Hg.
[ g]
Dalton’s Law

72. Dalton’s Laws: Additional Problems
27. A gaseous mixture made from 6.00 g of oxygen and 9.00 g of methane is placed in a 15.0 – L vessel at 0.00°C What is the partial pressure of each gas, and what is the total pressure in the vessel?
[0.281 atm O2; CH4; atm total]
28. A study of the effects of certain gases on plant growth requires a synthetic atmosphere composed of 1.5 mol percent of CO2, 18.0 mol percent O2; and 80.5 mol percent of Ar. (a) calculate the partial pressure of O2 in the mixture if the total pressure of the atmosphere is to be 745 torr. (b) If this atmosphere is to be held in a 120 –L space at 295 K, how many moles of O2 are needed?
[PO2 = 134 torr; nO2 = mol]

73. Dalton’s law of Partial Pressure
29. The apparatus shown consists of three bulbs connected by stopcocks. What is the pressure inside the system when the stopcocks are opened? Assume that the lines connecting the bulbs have zero volume and that the temperature remains constants.
[PCO2 = atm; PH2 = atm; P Ar = atm; PT = atm]

74. When these valves are opened, what is the partial pressure
Example 30
4.00 L
CH4
3.50 L O2
1.50 L N2
2.70 atm
.58 atm
.752 atm
When these valves are opened, what is the partial pressure
of each gas and the total pressure in the assembly?
[P of CH4 = 1.2 atm; P of N2 = atm;
P of O2 = atm; P total : add all the pressures]

75. Kinetic Molecular Theory of Gases
Gas particles are in continuous motion ( the hotter the gas, the faster the molecules are moving) with negligible volume compared to volume of container.
Molecules are far apart from each other
Do not attract or repulse each other (?).
All collisions are elastic (gas does not lose energy when left alone).
The energy is proportional to Kelvin temperature. At a given temperature all gases have the same average KE.

76. Properties of Gases Observation Hypothesis Gases are easy to expand
Gas molecules do not strongly attract each other
Gases are compressible
Particles have small volumes compared to continer. Lots of empty space
Gases are easy to compress
Gas molecules don’t strongly repel each other
Gases have densities that are 1/1000 of solid or liquid densities
Molecules are much farther apart in gases than in liquids and solids
Hot gases leak through holes faster than cold gases
Gas molecules are in constant motion

77. Properties of Gases Observation Hypothesis
Gases undergo elastic collisions: when gas is left alone at constnat temperature, it does not liquefy or vaporize (no energy exchange)
Gas molecules are like billiard balls – do not stick to each other (do not attract, do not repel)
Hot gases leak through holes faster than cold gases
Gas molecules are in constant motion

78. Kinetic Molecular Theory of Gases
Ideal gas limitations:
Gases can be liquefied if cooled enough.
Real gas molecules do attract one another to some extent otherwise the particles would not condense to form a liquid.

79. Maxwell Distribution Curves
Average Kinetic Energy at a given temperature is constant for a gas sample
But, the speeds of the molecules vary
(during to collisions with each other and with the walls of the container)
Physics: momentum is conserved
(playing pool)

80. Maxwell’s Distribution Curves

81. Gas Laws: Maxwell’s Distribution Curves
Molecules in a gas move at different speeds.
The Maxwell Distribution Curves show how many molecules are moving at a particular speed.
The distribution shifts to higher speeds at higher temperatures.
377 m/s
900 m/s
compare
1500 m/s

82. MKT of Gases: Equations
KE = ½ m(urms)2
Average KE = (3/2) RT
Maxwell equation for the root mean square velocity:
Urms =
The Urms is not the same as the mean (average ) speed. The difference is small.

83. Average Molecular speed
Average molecular kinetic energy depends only on temperature for ideal gases.
Therefore:
Higher temperature = higher root-mean- square speed (RMS), rms
Higher molecular weight (molar mass) = lower urms speed (same temperature)

84. Average Root Mean Square: Examples
31. Calculate the Urms speed, urms, of an N2 molecule at 25ºC.
(5.15 x 102 m/s)
32. Calculate the urms speed of helium atoms 25ºC (1.36 x 103 m/s)
33. Calculate the Urms speed of chlorine atoms at 25ºC (323 m/s)

85. Average Speed of Some Molecules

86. Diffusion and Effusion
(a) Diffusion: mixing of gas molecules by random motion under conditions where molecular collisions occur.
(Ib) Effusion: the escape of a gas through a pinhole without molecular collisions

87. Diffusion and Effusion
HCl and NH3: What will happen?

88. Graham’s Law of Diffusion
Under the same conditions of temperature and pressure, the rate of diffusion of gas molecules are inversely proportional to the square root of their molecular masses.

89. Graham’s Law of Diffusion
34. It has taken 192 seconds for 1.4 L of an unknown gas to effuse through a porous wall and 84 seconds for the same volume of N2 gas to effuse at the same temperature and pressure. What is the molar mass of the unknown gas? (146 g/mol)
35. In a given period of time, 0.21 moles of a gas of MM = 26 gmol-1 effuses. How many moles of HCN would effuse in the same period of time?
36. Calculate and compare the urms of Nitrogen gas at 35oC and 299K.

90. Real Gases
Problems with the Kinetic Molecular Theory of "Ideal" Gases:
1. Gas particles have volume (they are not point masses). The volume becomes important under certain conditions.
2. When gas particles are close to each other, they attract each other.

91. PV = nRT equation when rearranged:
For 1 mole of gas:
PV = nRT equation when rearranged:
Plot of (PV)/(RT) for
1 mole of gas
The value for the equation is not always equal to 1
Corrections to the Ideal Gas Equation is needed

92. Factors that Affect Ideality
Deviation from ideal behavior as a function of temperature for nitrogen gas:

93. Factors that Affect Ideality of Gases
Interactions between the molecules (intermolecular forces): important at low temperatures and small free volume
Actual volumes of the molecules: important at high pressures and small free volume.
Free volume: the space in the container that is not occupied by the molecules.

94. Factors Affecting Ideality of Gases: low temperatures and small free volumes
Distance between molecules is related to gas concentration:
At high concentration (high P, low V):
Molecules are closer (higher concentration) = stronger intermolecular attractions = deviation from ideality
Repulsion make pressure higher than expected by decreasing free volume
Attractions make pressure lower than expected by breaking molecular collisions (plastic collisions)

95. Effect of Intermolecular Attractions
Orange molecules attract purple molecules.
Therefore: purple molecule exert less force when it collides with the wall.
No attractive forces = more force

96. Real Gases: Effect of Pressure
At high pressures
Intermolecular distances between molecules decrease
Attractive forces start to play a role
Stickiness factor
Measured pressure is less than expected
Correction for lower pressure

97. Real Gases: Effect of Volume
Volume should go to zero, but it does not.
At low pressure, the gas occupies the entire container and its volume is insignificant compared to the volume of the container.
At high pressure, the volume of a real gas is somewhat larger than the ideal value for an ideal gas as gas molecules take up space.

98. Correction due to volume: (V – nb)
V = volume of the container
n = number of moles
B = volume of a mole of particles
Correction for volume

99. Real Gases: Corrections
Constant needed to correct intermolecular attractive forces (make it larger)
Constant needed to correct for volume of individual gas molecules (make it smaller)
The constants are characteristic properties of the substances: depend on the make-up and geometry of the substance

100. Van der Waals Constants for Common Gases
Compound
   
a (L2-atm/mol2)   
b (L/mol) He Ne
0.2107 H2
0.2444 Ar
1.345 O2
1.360 N2
1.390 CO
1.485
CH4
2.253
CO2
3.592
NH3
4.170

101. Real Gases: Comparison
Ideal gas
Real gas
Obey PV=nRT
Always
Only at low pressures
Molecular volume
Zero
Small, but not zero
Molecular attraction
Small
Molecular repulsion
small

102. Real Gases Large deviation form ideality:
Large intermolecular attractive forces (IMF)
Large Molar Mass (and subsequently volume)
Real Conditions:
high pressures
low volumes
Ideal Conditions:
Low pressures (atmospheric and up to ≈ 50 atm
High temperatures

103. The End

105. Factors Affecting Ideality of Gases
Tug-of-war between these two effects causes the following:
Repulsion win at very high pressure
Attractions win at moderate pressure
Neither attractions nor repulsions are important at low pressure.

106. 22.41 L atm O2 CO2 PV P (at constant T)
PV versus P at Constant T (1 mole of Gas)
22.41 L atm O2
CO2 PV
P (at constant T)

107. V of a real gas > V of an ideal gas because V of gas molecules is significant when P is high.  Ideal Gas Equation assumes that the individual gas molecules have no volume.

108. Boyle’s Law

109. Plots of Charles’ Law
A plot of V versus T for a gas sample. What type of graph?

110. Kinetic Molecular Theory of Gases
1. Gases are composed of tiny atoms or molecules (particles) whose size is negligible compared to the average distance between them. This means that the volume of the individual particles in a gas can be assumed to be negligible (close to zero).
2. The particles move randomly in straight lines in all directions and at various speeds.
3. The forces of attraction or repulsion between two particles in a gas are very weak or negligible (close to zero), except when they collide.
4. When particles collide with one another, the collisions are elastic (no kinetic energy is lost). The collisions with the walls of the container create the gas pressure.
5. The average kinetic energy of a molecule is proportional to the Kelvin temperature and all calculations should be carried out with temperatures converted to K.

111. Notes: Kinetic Molecular Theory of Gases
The observation that gases are compressible agrees with the assumption that gas particles have a small volume compared to the container.
b. Elastic collisions agree with the observation that gases when left alone in a container do not seem to lose energy and do not spontaneously convert to the liquid.
c. The assumptions have limitations. For example, gases can be liquefied if cooled enough. This means real gas molecules do attract one another to some extent otherwise the particles would never stick to one another in order to condense to form a liquid.

112. Measuring Pressure
Open-ended Manometer
Mercury Barometer
Pressure?

113. Maxwell- Boltzmann Velocity (energy) Distribution
Plot of Probability (fraction of molecules with given speed) versus root mean square velocity of the molecules.

114. Maxwell Distribution Curve
Variation in particle speeds for hydrogen gas at 273K
urms
The vertical line on the graph represents the root-mean-square-speed (urms).
The root-mean-square-speed is the square root of the averages of the squares of the speeds of all the particles in a gas sample at a particular temperature.