1. Gases
Chapters 12.1 and 13

2. 12.1 Main Idea
Gases expand, diffuse, exert pressure, and can be compressed because they are in a low-density state consisting of tiny, constantly moving particles

3. Objectives
Predict the behavior of gases using the kinetic-molecular theory
Explain how mass affects the rates of diffusion and effusion
Calculate the partial pressure of a gas
Measure gas pressure

4. Review Vocabulary
Kinetic energy
Molar mass

5. New Vocabulary Kinetic-molecular theory Elastic collision Temperature
Diffusion
Graham’s Law
Pressure
Barometer
Manometer
Pascal (Pa)
Dalton's law of partial pressure
Atmosphere (atm)

6. Kinetic-Molecular (KM) Theory
Assumptions
Particle size is very small
Particles take up relatively no space
Particles are far apart
Very little interaction of particles
Collisions are elastic
No kinetic energy is lost in a collision

7. Particle Energy Determined by mass and velocity
Temperature- the average kinetic energy of particles in matter

8. Behavior of Gases
Pressure- gases will expand to fill the space they occupy

9. Behavior of Gases
Compression and expansion- density of material can be changed by changing the available volume

10. Behavior of Gases Diffusion- movement of one material through another
Concentration gradient
Effusion- gas escaping from a confined space through tiny openings

11. What is the ratio of the rate of diffusion for ammonia and hydrogen chloride?

12. Calculate the ratio of effusion rates for nitrogen gas and neon
RH/RHe = 0.849

13. Pressure
Pressure (P) is defined as the force per unit area on a surface. (P=F/A)
Gas pressure is caused by collisions of the gas molecules with each other and with surfaces with which they come into contact.
The pressure exerted by a gas depends on volume, temperature, and the number of molecules present.
The greater the number of collisions of gas molecules, the higher the pressure will be.

14. Gas Pressure Barometer Manometer
Barometers measure atmospheric pressure
open system
Manometers measure gas pressure in a closed system

15. Gas Pressure Units Pascal (1 Pa = 1 /m2)
Atmosphere (1 atm = kPa)
mm Hg (1 atm = 760 mm Hg)
Torr (1 torr = 1 mm Hg)

16. Dalton’s Law of Partial Pressures
total pressure is the sum of the partial pressures
Ptot=P1 + P2 + P3 + … Pn

18. A mixture of O2, CO2 and N2 has a total pressure of 0. 97 atm
A mixture of O2, CO2 and N2 has a total pressure of 0.97 atm. What is the partial pressure of O2 if the partial pressure of CO2 is 0.70 atm and the partial pressure of N2 is 0.12 atm?
0.97 atm = 0.70 atm atm + x
X = 0.15 atm

19. Can you…
Predict the behavior of gases using the kinetic-molecular theory
Explain how mass affects the rates of diffusion and effusion
Calculate the partial pressure of a gas
Measure gas pressure

20. The Gas Laws
Chapter 13.1

21. 13.1 Main Idea
For a fixed amount of gas, a change in one variable- pressure, volume or temperature- affects the other two.

22. 13.1 Objectives
State the relationships among pressure, volume, temperature, and the amount of gas
Apply gas laws to problems involving pressure, volume, temperature, and the amount of gas
Create graphs of the relationships among pressure, volume, temperature, and the amount of gas
Solve problems related to fixed amounts of gases

23. Review Vocabulary Scientific law Directly related
Indirectly (inversely) related
Kelvin

24. New Vocabulary Ideal gas Absolute zero Boyle’s law Charles’s law
Gay-Lussac’s law
Combined gas law

25. Ideal gas Non-existent, but assumes the following:
Completely elastic collisions
Particles occupy no volume
Large number of particles
No attractive or repellent forces between particles
Molecules are in completely random motion

26. Boyle’s Law Constants: amount of gas (n) and temperature (T)
Boyle's Law in Motion

27. A diver blows a 0. 75 L air bubble 10 m under water
A diver blows a 0.75 L air bubble 10 m under water. As it rises, the pressure goes from 2.25 atm to 1.03 atm. What is the volume of the bubble at the surface?
P1V1=P2V2
2.25 atm
0.75 L
= 1.6 L
1.03 atm

28. Charles’s Law Constants: amount of gas (n) and pressure (P)
Temperature is in Kelvin (K)
K= C
Charles' Law in Motion

29. A helium balloon in a closed car occupies a volume or 2. 32 L at 40°C
A helium balloon in a closed car occupies a volume or 2.32 L at 40°C. If the temperature rises to 75°C, what is the new volume of the balloon?
V2=V1T2/T1
348.0 K
2.32 L
= 2.58 L
313.0 K

30. Gay-Lussac’s Law Constants: amount of gas (n) and volume (V)
T must be in Kelvin
Gay-Lussac in Motion

31. The pressure of oxygen gas inside a canister is 5. 00 atm at 25°C
The pressure of oxygen gas inside a canister is 5.00 atm at 25°C. the canister is placed in a cold environment where the temperature is -10°C; what is the new pressure in the canister?
P2=P1T2/T1
263.0 K
5.00 atm
= 4.41 atm
298.0 K

32. Predict
The relationship between pressure and amount of gas at a fixed temperature and volume
Pressure-Moles relationship
The relationship between volume and the amount of gas at a fixed temperature and amount of gas
Volume-Moles relationship

33. Combined Gas Law
Combination of Boyle’s, Charles’, and Gay-Lussac’s laws

34. A gas at 110 kPa and 30.0°C fills a flexible container with an initial volume of 2.00L. If the temperature is raised to 80.0°C and the pressure increases to 440 kPa, what is the new volume?
0.58 L

35. Gas Law Summary Law Boyle’s Charles’ Gay-Lussac’s Combined Formula
Constant
Moles, temp
Moles, pressure
Moles, volume
Moles
Graphic
Volume
Temperature
Pressure
Volume
Temperature
Pressure
Volume
Temperature
Pressure
Volume
Temperature
Pressure

36. Can you…
State the relationships among pressure, volume, temperature, and the amount of gas
Apply gas laws to problems involving pressure, volume, temperature, and the amount of gas
Create graphs of the relationships among pressure, volume, temperature, and the amount of gas
Solve problems related to fixed amounts of gases

37. Ideal Gas Law
13.2

38. 13.2 Main Idea
The ideal gas law relates the number of particles to pressure, temperature, and volume

39. 13.2 Objectives
Relate the number of particles and volume using Avogadro’s principle
Relate the amount of gas present to its pressure, temperature, and volume using the ideal gas law
Compare and contrast the properties of real gases and ideal gases
Solve problems using the ideal gas law

40. Review Vocabulary
Mole
Molar mass (M)

41. New Vocabulary STP Avogadro’s principle Molar volume
Ideal gas constant (R)
Ideal gas law

42. STP Standard temperature and pressure Standard temperature
°C = K
Standard pressure
1 atm = 760 torr = kPa

43. Avogadro’s Principle
Equal volumes of (ideal) gases, at the same temperature and pressure, contain equal numbers of particles
1 mol gas = 22.4 L at STP

44. How much volume do the following gases fill at STP
1 mol CH4
1 mol CO2
1 mol H2O
1 mol Ne
2 mol He
1 mol O2

45. Molar Volume
The main component of natural gas used for home heating and cooking is methane (CH4). Calculate the volume that 2.00 kg of methane will occupy at STP.
M = m/n
M = molar mass
m = mass
n = number of moles

46. The main component of natural gas used for home heating and cooking is methane (CH4). Calculate the volume that 2.00 kg of methane will occupy at STP.
Molar mass (M) = g/mol (C + 4H)

47. Molar mass (M) = 16.05 g/mol (C + 4H) Number of moles (n) = ?? M = m/n
The main component of natural gas used for home heating and cooking is methane (CH4). Calculate the volume that 2.00 kg of methane will occupy at STP.
Molar mass (M) = g/mol (C + 4H)
Number of moles (n) = ??
M = m/n
n = m/M
2000 g CH4
1 mol
= 125 mol
16.05 g

48. Molar mass (M) = 16.05 g/mol (C + 4H) Number of moles (n) = 125 mol
The main component of natural gas used for home heating and cooking is methane (CH4). Calculate the volume that 2.00 kg of methane will occupy at STP.
Molar mass (M) = g/mol (C + 4H)
Number of moles (n) = 125 mol
2000 g CH4
1 mol
= 125 mol
16.05 g

49. Molar mass (M) = 16.05 g/mol (C + 4H) Number of moles (n) = 125 mol
The main component of natural gas used for home heating and cooking is methane (CH4). Calculate the volume that 2.00 kg of methane will occupy at STP.
Molar mass (M) = g/mol (C + 4H)
Number of moles (n) = 125 mol
Molar volume = ??
125 mol
22.4 L
= 2800 L
1 mol

50. Ideal Gas Law PV=nRT P = pressure (atm) V = volume (L)
n = number of moles of gas (mol)
R = gas constant (L•atm)/(mol•K)
T = temperature (K)

51. Calculate the number of moles of ammonia gas contained in a 3
Calculate the number of moles of ammonia gas contained in a 3.0 L vessel at 300 K with a pressure of 1.50 atm.
P = 1.50 atm; V = 3.0 L; n = ?; T = 300 K
R = (L•atm)/(mol•K)
N= PV/RT
1.50 atm (mol•K)
3.0 L
= 0.18 mol
(L•atm)
300 K

52. Molar mass and density
PV=nRT
n=m/M
PV=mRT/M
M=mRT/PV
D=m/V
D=MV/RT

53. Ideal gas and Real gases
Particles occupy no volume
All collisions are perfectly elastic
Infinitely large number of molecules
No forces between molecules
Particles occupy volume
KE is lost during collisions
Limited numbers of molecules
Inter-molecular forces exist

54. Can you…
Relate the number of particles and volume using Avogadro’s principle
Relate the amount of gas present to its pressure, temperature, and volume using the ideal gas law
Compare and contrast the properties of real gases and ideal gases
Solve problems using the ideal gas law

55. Gas Stoichiometry
13.3

56. Main Idea
When gases react, the coefficients in the balanced chemical equation represent both molar amounts and the relative volumes.

57. 13.3 Objectives
Determine volume ratios for gaseous reactants and products by using coefficients from chemical equations
Apply gas laws to calculate amounts of gaseous reactants and products in a chemical reaction

58. Review Vocabulary
Stoichiometry
Coefficient
Chemical equation

59. Stoichiometry with Gases
Only works with gases!
2H2 (g) + O2 (g)  2 H2O (g)
2 moles of hydrogen + 1 mole of oxygen react to form 2 moles of water
2 liters of hydrogen + 1 liter of oxygen react to form 2 liters of water

60. What volume of oxygen gas is needed for the complete combustion of 4
What volume of oxygen gas is needed for the complete combustion of 4.00 L of propane gas assuming that pressure and temperature are constant?
C3H8(g) + 5 O2(g) 3 CO2(g) + 4 H2O(g)
4.00 L C3H8
5 L O2
= 20.0 L O2
1 L C3H8

61. Can you…
Determine volume ratios for gaseous reactants and products by using coefficients from chemical equations
Apply gas laws to calculate amounts of gaseous reactants and products in a chemical reaction

62. Can you…
Predict the behavior of gases using the kinetic-molecular theory
Explain how mass affects the rates of diffusion and effusion
Calculate the partial pressure of a gas
Measure gas pressure
State the relationships among pressure, volume, temperature, and the amount of gas
Apply gas laws to problems involving pressure, volume, temperature, and the amount of gas
Create graphs of the relationships among pressure, volume, temperature, and the amount of gas
Solve problems related to fixed amounts of gases
Relate the number of particles and volume using Avogadro’s principle
Relate the amount of gas present to its pressure, temperature, and volume using the ideal gas law
Compare and contrast the properties of real gases and ideal gases
Solve problems using the ideal gas law
Determine volume ratios for gaseous reactants and products by using coefficients from chemical equations
Apply gas laws to calculate amounts of gaseous reactants and products in a chemical reaction