2. John C. Kotz State University of New York, College at Oneonta John C. Kotz Paul M. Treichel John Townsend http://academic.cengage.com/kotz Chapter 11 Gases and Their Properties

3. Important – Read Before Using Slides in Class Instructor: This PowerPoint presentation contains photos and figures from the text, as well as selected animations and videos. For animations and videos to run properly, we recommend that you run this PowerPoint presentation from the PowerLecture disc inserted in your computer. Also, for the mathematical symbols to display properly, you must install the supplied font called “Symb_chm,” supplied as a cross-platform TrueType font in the “Font_for_Lectures” folder in the "Media" folder on this disc. If you prefer to customize the presentation or run it without the PowerLecture disc inserted, the animations and videos will only run properly if you also copy the associated animation and video files for each chapter onto your computer. Follow these steps: 1.Go to the disc drive directory containing the PowerLecture disc, and then to the “Media” folder, and then to the “PowerPoint_Lectures” folder. 2.In the “PowerPoint_Lectures” folder, copy the entire chapter folder to your computer. Chapter folders are named “chapter1”, “chapter2”, etc. Each chapter folder contains the PowerPoint Lecture file as well as the animation and video files. For assistance with installing the fonts or copying the animations and video files, please visit our Technical Support at http://academic.cengage.com/support or call (800) 423-0563. Thank you. http://academic.cengage.com/support

4. 3 © 2009 Brooks/Cole - Cengage BEHAVIOR OF GASES Chapter 11

5. 4 © 2009 Brooks/Cole - Cengage Importance of Gases Airbags fill with N 2 gas in an accident.Airbags fill with N 2 gas in an accident. Gas is generated by the decomposition of sodium azide, NaN 3.Gas is generated by the decomposition of sodium azide, NaN 3. 2 NaN 3 f 2 Na + 3 N 22 NaN 3 f 2 Na + 3 N 2 PLAY MOVIE

6. 5 © 2009 Brooks/Cole - Cengage Hot Air Balloons — How Do They Work? PLAY MOVIE

7. 6 © 2009 Brooks/Cole - Cengage THREE STATES OF MATTER PLAY MOVIE

8. 7 © 2009 Brooks/Cole - Cengage General Properties of Gases There is a lot of “free” space in a gas.There is a lot of “free” space in a gas. Gases can be expanded infinitely.Gases can be expanded infinitely. Gases occupy containers uniformly and completely.Gases occupy containers uniformly and completely. Gases diffuse and mix rapidly.Gases diffuse and mix rapidly.

9. 8 © 2009 Brooks/Cole - Cengage Properties of Gases Gas properties can be modeled using math. Model depends on— V = volume of the gas (L)V = volume of the gas (L) T = temperature (K)T = temperature (K) n = amount (moles)n = amount (moles) P = pressure (atmospheres)P = pressure (atmospheres)

10. 9 © 2009 Brooks/Cole - Cengage Pressure Pressure of air is measured with a BAROMETER (developed by Torricelli in 1643)

11. 10 © 2009 Brooks/Cole - Cengage Pressure Hg rises in tube until force of Hg (down) balances the force of atmosphere (pushing up). P of Hg pushing down related to Hg densityHg density column heightcolumn height

12. 11 © 2009 Brooks/Cole - Cengage Pressure Column height measures P of atmosphere 1 standard atm = 760 mm Hg1 standard atm = 760 mm Hg = 29.9 inches Hg = about 34 feet of water SI unit is PASCAL, Pa, where 1 atm = 101.325 kPa

13. 12 © 2009 Brooks/Cole - Cengage IDEAL GAS LAW Brings together gas properties. Can be derived from experiment and theory. P V = n R T

14. 13 © 2009 Brooks/Cole - Cengage Boyle’s Law If n and T are constant, then PV = (nRT) = k This means, for example, that P goes up as V goes down. Robert Boyle (1627-1691). Son of Earl of Cork, Ireland.

15. 14 © 2009 Brooks/Cole - Cengage Boyle’s Law A bicycle pump is a good example of Boyle’s law. As the volume of the air trapped in the pump is reduced, its pressure goes up, and air is forced into the tire. PLAY MOVIE

16. 15 © 2009 Brooks/Cole - Cengage Charles’s Law If n and P are constant, then V = (nR/P)T = kT V and T are directly related. Jacques Charles (1746- 1823). Isolated boron and studied gases. Balloonist.

17. 16 © 2009 Brooks/Cole - Cengage Charles’s original balloon Modern long-distance balloon

18. 17 © 2009 Brooks/Cole - Cengage Charles’s Law Balloons immersed in liquid N 2 (at -196 ˚C) will shrink as the air cools (and is liquefied).

19. 18 © 2009 Brooks/Cole - Cengage Charles’s Law PLAY MOVIE

20. 19 © 2009 Brooks/Cole - Cengage Avogadro’s Hypothesis Equal volumes of gases at the same T and P have the same number of molecules. V = n (RT/P) = kn V and n are directly related. twice as many molecules

21. 20 © 2009 Brooks/Cole - Cengage Avogadro’s Hypothesis The gases in this experiment are all measured at the same T and P. 2 H 2 (g) + O 2 (g) 2 H 2 O(g) ff f PLAY MOVIE

22. 21 © 2009 Brooks/Cole - Cengage Combining the Gas Laws V proportional to 1/PV proportional to 1/P V prop. to TV prop. to T V prop. to nV prop. to n Therefore, V prop. to nT/PTherefore, V prop. to nT/P V = 22.4 L for 1.00 mol whenV = 22.4 L for 1.00 mol when –Standard pressure and temperature (STP) –T = 273 K –P = 1.00 atm

23. 22 © 2009 Brooks/Cole - Cengage Using PV = nRT How much N 2 is req’d to fill a small room with a volume of 960 cubic feet (27,000 L) to P = 745 mm Hg at 25 o C? R = 0.082057 Latm/Kmol R = 0.082057 Latm/KmolSolution 1. Get all data into proper units V = 27,000 L V = 27,000 L T = 25 o C + 273 = 298 K T = 25 o C + 273 = 298 K P = 745 mm Hg (1 atm/760 mm Hg) = 0.98 atm P = 745 mm Hg (1 atm/760 mm Hg) = 0.98 atm

24. 23 © 2009 Brooks/Cole - Cengage Using PV = nRT How much N 2 is req’d to fill a small room with a volume of 960 cubic feet (27,000 L) to P = 745 mm Hg at 25 o C? R = 0.082057 Latm/Kmol R = 0.082057 Latm/KmolSolution 2. Now calc. n = PV / RT n = 1.1 x 10 3 mol (or about 30 kg of gas)

25. 24 © 2009 Brooks/Cole - Cengage Gases and Stoichiometry 2 H 2 O 2 (liq) f 2 H 2 O(g) + O 2 (g) Decompose 0.11 g of H 2 O 2 in a flask with a volume of 2.50 L. What is the pressure of O 2 at 25 o C? Of H 2 O? Bombardier beetle uses decomposition of hydrogen peroxide to defend itself.

26. 25 © 2009 Brooks/Cole - Cengage Gases and Stoichiometry 2 H 2 O 2 (liq) f 2 H 2 O(g) + O 2 (g) Decompose 0.11 g of H 2 O 2 in a flask with a volume of 2.50 L. What is the pressure of O 2 at 25 o C? Of H 2 O? Solution Strategy: Calculate moles of H 2 O 2 and then moles of O 2 and H 2 O. Finally, calc. P from n, R, T, and V.

27. 26 © 2009 Brooks/Cole - Cengage Gases and Stoichiometry 2 H 2 O 2 (liq) f 2 H 2 O(g) + O 2 (g) Decompose 0.11 g of H 2 O 2 in a flask with a volume of 2.50 L. What is the pressure of O 2 at 25 o C? Of H 2 O? Solution

28. 27 © 2009 Brooks/Cole - Cengage Gases and Stoichiometry 2 H 2 O 2 (liq) f 2 H 2 O(g) + O 2 (g) Decompose 0.11 g of H 2 O 2 in a flask with a volume of 2.50 L. What is the pressure of O 2 at 25 o C? Of H 2 O? Solution P of O 2 = 0.016 atm

29. 28 © 2009 Brooks/Cole - Cengage Gases and Stoichiometry What is P of H 2 O? Could calculate as above. But recall Avogadro’s hypothesis. V  n at same T and P P  n at same T and V There are 2 times as many moles of H 2 O as moles of O 2. P is proportional to n. Therefore, P of H 2 O is twice that of O 2. P of H 2 O = 0.032 atm 2 H 2 O 2 (liq) f 2 H 2 O(g) + O 2 (g)

30. 29 © 2009 Brooks/Cole - Cengage Dalton’s Law of Partial Pressures What is the total pressure in the flask? P total in gas mixture = P A + P B +... Therefore, P total = P(H 2 O) + P(O 2 ) = 0.048 atm Dalton’s Law: total P is sum of PARTIAL pressures. 2 H 2 O 2 (liq) f 2 H 2 O(g) + O 2 (g) 0.032 atm 0.016 atm 0.032 atm 0.016 atm

31. 30 © 2009 Brooks/Cole - Cengage Dalton’s Law John Dalton 1766-1844

32. 31 © 2009 Brooks/Cole - Cengage GAS DENSITY Higher Density air Low density helium PLAY MOVIE

33. 32 © 2009 Brooks/Cole - Cengage GAS DENSITY PV = nRT d and M proportional and density (d) = m/V

34. 33 © 2009 Brooks/Cole - Cengage The Disaster of Lake Nyos Lake Nyos in Cameroon was a volcanic lake. CO 2 built up in the lake and was released explosively on August 21, 1986. 1700 people and hundreds of animals died. See Chapter 14 for more information

35. 34 © 2009 Brooks/Cole - Cengage USING GAS DENSITY The density of air at 15 o C and 1.00 atm is 1.23 g/L. What is the molar mass of air? 1. Calc. moles of air. V = 1.00 LP = 1.00 atmT = 288 K V = 1.00 LP = 1.00 atmT = 288 K n = PV/RT = 0.0423 mol n = PV/RT = 0.0423 mol 2. Calc. molar mass mass/mol = 1.23 g/0.0423 mol = 29.1 g/mol mass/mol = 1.23 g/0.0423 mol = 29.1 g/mol

36. 35 © 2009 Brooks/Cole - Cengage KINETIC MOLECULAR THEORY (KMT) Theory used to explain gas laws. KMT assumptions are Gases consist of molecules in constant, random motion.Gases consist of molecules in constant, random motion. P arises from collisions with container walls.P arises from collisions with container walls. No attractive or repulsive forces between molecules. Collisions elastic.No attractive or repulsive forces between molecules. Collisions elastic. Volume of molecules is negligible.Volume of molecules is negligible.

37. 36 © 2009 Brooks/Cole - Cengage Kinetic Molecular Theory Because we assume molecules are in motion, they have a kinetic energy. KE = (1/2)(mass)(speed) 2 At the same T, all gases have the same average KE. As T goes up for a gas, KE also increases — and so does speed.

38. 37 © 2009 Brooks/Cole - Cengage Kinetic Molecular Theory At the same T, all gases have the same average KE. As T goes up, KE also increases — and so does speed. PLAY MOVIE

39. 38 © 2009 Brooks/Cole - Cengage Kinetic Molecular Theory where u is the speed and M is the molar mass. speed INCREASES with Tspeed INCREASES with T speed DECREASES with Mspeed DECREASES with M Maxwell’s equation Root mean square speed

40. 39 © 2009 Brooks/Cole - Cengage Distribution of Gas Molecule Speeds Boltzmann plotsBoltzmann plots Named for Ludwig Boltzmann doubted the existence of atoms.Named for Ludwig Boltzmann doubted the existence of atoms. This played a role in his suicide in 1906. This played a role in his suicide in 1906. PLAY MOVIE

41. 40 © 2009 Brooks/Cole - Cengage Velocity of Gas Molecules Molecules of a given gas have a range of speeds.

42. 41 © 2009 Brooks/Cole - Cengage Velocity of Gas Molecules Average velocity decreases with increasing mass.

43. 42 © 2009 Brooks/Cole - Cengage GAS DIFFUSION AND EFFUSION DIFFUSION is the gradual mixing of molecules of different gases.

44. 43 © 2009 Brooks/Cole - Cengage GAS EFFUSION See Figure 11.19 EFFUSION is the movement of molecules through a small hole into an empty container.

45. 44 © 2009 Brooks/Cole - Cengage GAS DIFFUSION AND EFFUSION Molecules effuse thru holes in a rubber balloon, for example, at a rate (= moles/time) that is proportional to Tproportional to T inversely proportional to M.inversely proportional to M. Therefore, He effuses more rapidly than O 2 at same T. He

46. 45 © 2009 Brooks/Cole - Cengage GAS DIFFUSION AND EFFUSION Graham’s law governs effusion and diffusion of gas molecules. Thomas Graham, 1805-1869. Professor in Glasgow and London. Rate of effusion is inversely proportional to its molar mass.

47. 46 © 2009 Brooks/Cole - Cengage Gas Diffusion relation of mass to rate of diffusion HCl and NH 3 diffuse from opposite ends of tube. Gases meet to form NH 4 Cl HCl heavier than NH 3 Therefore, NH 4 Cl forms closer to HCl end of tube. HCl and NH 3 diffuse from opposite ends of tube. Gases meet to form NH 4 Cl HCl heavier than NH 3 Therefore, NH 4 Cl forms closer to HCl end of tube. See Active Figure 11.18 PLAY MOVIE

48. 47 © 2009 Brooks/Cole - Cengage Using KMT to Understand Gas Laws Recall that KMT assumptions are Gases consist of molecules in constant, random motion.Gases consist of molecules in constant, random motion. P arises from collisions with container walls.P arises from collisions with container walls. No attractive or repulsive forces between molecules. Collisions elastic.No attractive or repulsive forces between molecules. Collisions elastic. Volume of molecules is negligible.Volume of molecules is negligible.

49. 48 © 2009 Brooks/Cole - Cengage Avogadro’s Hypothesis and Kinetic Molecular Theory P proportional to n — when V and T are constant PLAY MOVIE

50. 49 © 2009 Brooks/Cole - Cengage Gas Pressure, Temperature, and Kinetic Molecular Theory P proportional to T — when n and V are constant PLAY MOVIE

51. 50 © 2009 Brooks/Cole - Cengage Boyle’s Law and Kinetic Molecular Theory P proportional to 1/V — when n and T are constant PLAY MOVIE

52. 51 © 2009 Brooks/Cole - Cengage Deviations from Ideal Gas Law Real molecules have volume.Real molecules have volume. There are intermolecular forces.There are intermolecular forces. –Otherwise a gas could not become a liquid.

53. 52 © 2009 Brooks/Cole - Cengage Deviations from Ideal Gas Law Account for volume of molecules and intermolecular forces with VAN DER WAALS’s EQUATION. Measured V = V(ideal) Measured P intermol. forces vol. correction J. van der Waals, 1837-1923, Professor of Physics, Amsterdam. Nobel Prize 1910. nRT V - nb V 2 n 2 a P + ----- )(

54. 53 © 2009 Brooks/Cole - Cengage Deviations from Ideal Gas Law Cl 2 gas has a = 6.49, b = 0.0562 For 4.00 mol Cl 2 in a 4.00 L tank at 100.0 o C. P (ideal) = nRT/V = 30.6 atm P (van der Waals) = 26.0 atm