1. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu How to Use This Presentation To View the presentation as a slideshow with effects select “View” on the menu bar and click on “Slide Show.” To advance through the presentation, click the right-arrow key or the space bar. From the resources slide, click on any resource to see a presentation for that resource. From the Chapter menu screen click on any lesson to go directly to that lesson’s presentation. You may exit the slide show at any time by pressing the Esc key.

2. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter Presentation Transparencies Lesson Starters Standardized Test PrepVisual Concepts Sample Problems Resources

3. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Objectives Describe the process of diffusion. State Graham’s law of effusion. State the relationship between the average molecular velocities of two gases and their molar masses. Chapter 11 Section 4 Diffusion and Effusion

4. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Diffusion and Effusion The constant motion of gas molecules causes them to spread out to fill any container they are in. The gradual mixing of two or more gases due to their spontaneous, random motion is known as diffusion. Effusion is the process whereby the molecules of a gas confined in a container randomly pass through a tiny opening in the container. Chapter 11 Section 4 Diffusion and Effusion

5. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Click below to watch the Visual Concept. Visual Concept Comparing Diffusion and Effusion Chapter 11

6. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Graham’s Law of Effusion Rates of effusion and diffusion depend on the relative velocities of gas molecules. The velocity of a gas varies inversely with the square root of its molar mass. Recall that the average kinetic energy of the molecules in any gas depends only the temperature and equals. Chapter 11 Section 4 Diffusion and Effusion For two different gases, A and B, at the same temperature, the following relationship is true.

7. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Graham’s Law of Effusion From the equation relating the kinetic energy of two different gases at the same conditions, one can derive an equation relating the rates of effuses of two gases with their molecular mass: Chapter 11 Section 4 Diffusion and Effusion This equation is known as Graham’s law of effusion, which states that the rates of effusion of gases at the same temperature and pressure are inversely proportional to the square roots of their molar masses.

8. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Click below to watch the Visual Concept. Visual Concept Graham’s Law of Effusion Chapter 11

9. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Click below to watch the Visual Concept. Visual Concept Equation for Graham’s Law of Effusion Chapter 11

10. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Graham’s Law Section 4 Diffusion and Effusion Chapter 11

11. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Graham’s Law of Effusion, continued Sample Problem J Compare the rates of effusion of hydrogen and oxygen at the same temperature and pressure. Chapter 11 Section 4 Diffusion and Effusion

12. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Sample Problem J Solution Given: identities of two gases, H 2 and O 2 Unknown: relative rates of effusion Solution: The ratio of the rates of effusion of two gases at the same temperature and pressure can be found from Graham’s law. Chapter 11 Graham’s Law of Effusion, continued Section 4 Diffusion and Effusion

13. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Sample Problem J Solution, continued Substitute the given values into the equation: Hydrogen effuses 3.98 times faster than oxygen. Chapter 11 Graham’s Law of Effusion, continued Section 4 Diffusion and Effusion

14. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu End of Chapter 11 Show

15. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 1. Pressure can be measured in A.grams. B.meters. C.pascals. D.liters. Standardized Test Preparation Chapter 11 Multiple Choice

16. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 1. Pressure can be measured in A.grams. B.meters. C.pascals. D.liters. Chapter 11 Standardized Test Preparation Multiple Choice

17. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 2. A sample of oxygen gas has a volume of 150 mL when its pressure is 0.923 atm. If the pressure is increased to 0.987 atm and the temperature remains constant, what will the new volume be? A.140 mL B.160 mL C.200 mL D.240 mL Chapter 11 Standardized Test Preparation Multiple Choice

18. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 2. A sample of oxygen gas has a volume of 150 mL when its pressure is 0.923 atm. If the pressure is increased to 0.987 atm and the temperature remains constant, what will the new volume be? A.140 mL B.160 mL C.200 mL D.240 mL Chapter 11 Standardized Test Preparation Multiple Choice

19. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 3. What is the pressure exerted by a 0.500 mol sample of nitrogen in a 10.0 L container at 20°C? A.1.2 kPa B.10 kPa C.0.10 kPa D.120 kPa Chapter 11 Standardized Test Preparation Multiple Choice

20. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 3. What is the pressure exerted by a 0.500 mol sample of nitrogen in a 10.0 L container at 20°C? A.1.2 kPa B.10 kPa C.0.10 kPa D.120 kPa Chapter 11 Standardized Test Preparation Multiple Choice

21. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 4. A sample of gas in a closed container at a temperature of 100.0°C and 3.0 atm is heated to 300.0°C. What is the pressure of the gas at the higher temperature? A.35 atm B.4.6 atm C.59 atm D.9.0 atm Chapter 11 Standardized Test Preparation Multiple Choice

22. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 4. A sample of gas in a closed container at a temperature of 100.0°C and 3.0 atm is heated to 300.0°C. What is the pressure of the gas at the higher temperature? A.35 atm B.4.6 atm C.59 atm D.9.0 atm Chapter 11 Standardized Test Preparation Multiple Choice

23. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 5. An unknown gas effuses twice as fast as CH 4. What is the molar mass of the gas? A.64 g/mol B.32 g/mol C.8 g/mol D.4 g/mol Chapter 11 Standardized Test Preparation Multiple Choice

24. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 5. An unknown gas effuses twice as fast as CH 4. What is the molar mass of the gas? A.64 g/mol B.32 g/mol C.8 g/mol D.4 g/mol Chapter 11 Standardized Test Preparation Multiple Choice

25. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 6. If 3 L N 2 and 3 L H 2 are mixed and react according to the equation below, how many liters of unreacted gas remain? Assume temperature and pressure remain constant. N 2 (g) + 3H 2 (g)  2NH 3 (g) A.4 L B.3 L C.2 L D.1 L Chapter 11 Standardized Test Preparation Multiple Choice

26. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 6. If 3 L N 2 and 3 L H 2 are mixed and react according to the equation below, how many liters of unreacted gas remain? Assume temperature and pressure remain constant. N 2 (g) + 3H 2 (g)  2NH 3 (g) A. 4 L B.3 L C.2 L D.1 L Chapter 11 Standardized Test Preparation Multiple Choice

27. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 7. Avogadro’s law states that A.equal numbers of moles of gases at the same conditions occupy equal volumes, regardless of the identity of the gases. B.at constant pressure, gas volume is directly proportional to absolute temperature. C.the volume of a gas is inversely proportional to its amount in moles. D.at constant temperature, gas volume is inversely proportional to pressure. Chapter 11 Standardized Test Preparation Multiple Choice

28. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 7. Avogadro’s law states that A.equal numbers of moles of gases at the same conditions occupy equal volumes, regardless of the identity of the gases. B.at constant pressure, gas volume is directly proportional to absolute temperature. C.the volume of a gas is inversely proportional to its amount in moles. D.at constant temperature, gas volume is inversely proportional to pressure. Chapter 11 Standardized Test Preparation Multiple Choice

29. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 8. Give a molecular explanation for the observation that the pressure of a gas increases when the gas volume is decreased. Chapter 11 Standardized Test Preparation Short Answer

30. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 8. Give a molecular explanation for the observation that the pressure of a gas increases when the gas volume is decreased. Answer: The molecules are closer together, so they strike the walls of the container more often. Chapter 11 Standardized Test Preparation Short Answer

31. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 9. The graph on the next slide shows a plot of volume versus pressure for a particular gas sample at constant pressure. Answer the following questions by referring to the graph. No calculation is necessary. a.What is the volume of this gas sample at standard pressure? b.What is the volume of this gas sample at 4.0 atm pressure? c.At what pressure would this gas sample occupy a volume of 5.0 L? Chapter 11 Standardized Test Preparation Short Answer

32. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 9. continued Chapter 11 Standardized Test Preparation Short Answer

33. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 9. continued Chapter 11 Standardized Test Preparation Short Answer Answer: a. 2.0 L b. 0.5 L c. 0.4 atm

34. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 10.Refer to the plot in question 9. Suppose the same gas sample were heated to a higher temperature and a new graph of V versus P were plotted. Would the new plot be identical to this one? If not, how would it differ? Chapter 11 Standardized Test Preparation Extended Response

35. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 10.Refer to the plot in question 9. Suppose the same gas sample were heated to a higher temperature and a new graph of V versus P were plotted. Would the new plot be identical to this one? If not, how would it differ? Answer: The plot would not be identical to this one. It would have a similar shape, but would appear higher on the graph. This is because at any pressure, the volume would be higher at the higher temperature. Chapter 11 Standardized Test Preparation Extended Response