2. Warm Up zPick any element in group 1, 2, 7 or 8 and write down everything you know about it by looking at its position on the periodic table. *Think about electron configuration, chemical and physical properties, etc.

3. Reflection Questions zDid you meet the goal or goals you set for yourself last term? zAre you satisfied with the effort you put in during the last term zWhat are two goals you have for this term? yHow do you plan on achieving those goals?

4. Reflection Questions Cont. zWhat can Ms. Keeler do to help you achieve your goals? zIs there anything you wish was different about this class? (Be realistic)

5. Properties of Gases zWhat do you know about the properties of gases? zWrite down 3 properties of gases as you watch the following video. http://ed.ted.com/lessons/describing-the- invisible-properties-of-gas-brian-bennett

6. BEHAVIOR OF GASES Gases have mass Gases take up space Gases exert pressure Gases fill their containers Gases are mostly empty space (the molecules in a gas are separate, very small, and very far apart) Gases doing all of these things!

7. Kinetic Theory of Gases The basic assumptions of the kinetic molecular theory are:  Gases are mostly empty space  The molecules in a gas are separate, very small and very far apart

8. Kinetic Theory of Gases The basic assumptions of the kinetic molecular theory are:  Gas molecules are in constant, chaotic motion  Collisions between gas molecules are elastic (there is no energy gain or loss)

9. Kinetic Theory of Gases The basic assumptions of the kinetic molecular theory are:  The average kinetic energy of gas molecules is directly proportional to the absolute temperature  Gas pressure is caused by collisions of molecules with the walls of the container

10. Measurements of Gases  To describe a gas, its volume, amount, temperature, and pressure are measured. Volume: measured in L, mL, cm 3 (1 mL = 1 cm 3 ) Amount: measured in moles (mol), grams (g) Temperature: measured in KELVIN (K) K = ºC + 273 Pressure: measured in mm Hg, torr, atm, etc. P = F / A (force per unit area)

11. Bed of Nails http://www.youtube.com/watch?v=gReuTk qKC5w

12. Moderate Force (about 100 lbs) Small Area (0.0625 in 2 ) Enormous Pressure (1600 psi) P = F / A

13. Bed of Nails Large Surface Area (lots of nails) Moderate Force Small Pressure P = F / A

14. Units of Pressure  Units of Pressure:  1 atm = 760 mm Hg  1 atm = 760 torr  1 atm = 1.013 x 10 5 Pa  1 atm = 101.3 kPa  1 atm = 1.013 bar

15. Boyle’s Law As P , V  (when T and n are constant) and vice versa…. INVERSE RELATIONSHIP V  1/P P 1 V 1 = P 2 V 2 For a given number of molecules of gas at a constant temperature, the volume of the gas varies inversely with the pressure.

16. Example: A sample of gas occupies 12 L under a pressure of 1.2 atm. What would its volume be if the pressure were increased to 3.6 atm? (assume temp is constant)  P 1 V 1 = P 2 V 2  (1.2 atm)(12 L) = (3.6 atm)V 2  V 2 = 4.0 L

17. Charles’ Law Jacques Charles (1746-1828) The volume of a given number of molecules is directly proportional to the Kelvin temperature. As T , V  (when P and n are constant) and vice versa…. DIRECT RELATIONSHIP V  T

18. Example: A sample of nitrogen gas occupies 117 mL at 100.°C. At what temperature would it occupy 234 mL if the pressure does not change? (express answer in K and °C)  V 1 / T 1 = V 2 / T 2  (117 mL) / (373 K) = (234 mL) / T 2  T 2 = 746 K  T 2 = 473 ºC

19. Lab Design zDesign a lab to investigate the relationship between volume and temperature using any of the following supplies: zHot plate, balloon, ice, water, tape measurer, ruler, marker, various sized beakers and any other common laboratory items

20. Warm-up… zWhat is pressure? zDescribe Charles’ and Boyle’s law in words and write the equation for each zWhat type of relationship is each law.. Explain what happens, in general terms, to one variable based on the change in the other

21. Breathing zThink back to biology. How does breathing work? Try using the gas laws to explain. zWrite down two facts about breathing as you watch the following video. http://ed.ted.com/lessons/how-breathing- works-nirvair-kaur

22. Combined gas law This is for one gas undergoing changing conditions of temp, pressure, and volume. Combining Boyle’s law (pressure-volume) with Charles’ Law (volume-temp):

23. Example 1: A sample of neon gas occupies 105 L at 27°C under a pressure of 985 torr. What volume would it occupy at standard conditions?  P 1 = 985 torr  V 1 = 105 L  T 1 = 27 °C = 300. K  P 2 = 1 atm = 760 torr  V 2 = ?  T 2 = 0 °C = 273 K P 1 V 1 T 2 = P 2 V 2 T 1 (985 torr)(105 L)(273K) = (760torr)(V 2 )(300K) V 2 = 124 L

24. Example 2: A sample of gas occupies 10.0 L at 240°C under a pressure of 80.0 kPa. At what temperature would the gas occupy 20.0 L if we increased the pressure to 107 kPa?  P 1 = 80.0 kPa  V 1 = 10.0 L  T 1 = 240 °C = 513 K  P 2 = 107 kPa  V 2 = 20.0 L  T 2 = ? P 1 V 1 T 2 = P 2 V 2 T 1 (80.0kPa)(10.0L)(T 2 ) = (107kPa)(20.0L)(513K) T 2 = 1372K≈ 1370K

25. Example 3: A sample of oxygen gas occupies 23.5 L at 22.2 °C and 1.3 atm. At what pressure (in mm Hg) would the gas occupy 11.6 L if the temperature were lowered to 12.5 °C?  P 1 = 1.3 atm  V 1 = 23.5 L  T 1 = 22.2 °C = 295.2 K  P 2 = ?  V 2 = 11.6 L  T 2 = 12.5 °C = 285.5 K P 1 V 1 T 2 = P 2 V 2 T 1  P 2 = P 1 V 1 T 2 /V 2 T 1 P 2 =(1.3 atm x (760mm Hg/1atm))(23.5L)(285.5K) (11.6L)(295.2K) = P 2 = 1936 mm Hg ≈ 1900 mmHg

26. Gases: Standard Molar Volume & The Ideal Gas Law  Avogadro’s Law: at the same temperature and pressure, equal volumes of all gases contain the same # of molecules (& moles).  Standard molar volume = 22.4 L @STP  This is true of “ideal” gases at reasonable temperatures and pressures,the behavior of many “real” gases is nearly ideal.

27. The IDEAL GAS LAW  Shows the relationship among the pressure, volume, temp. and # moles in a sample of gas.  P = pressure (atm)  V = volume (L)  n = # moles  T = temp (K)  R = universal gas constant = 0.0821 The units of R depend on the units used for P, V & T

28. Example 1: What volume would 50.0 g of ethane, C 2 H 6, occupy at 140 ºC under a pressure of 1820 torr?  P = (1820 torr)(1 atm/760 torr) = 2.39 atm  V = ?  n = (50.0 g)(1 mol / 30.08 g) = 1.66 mol  T = 140 °C + 273 = 413 K PV = nRT  V = nRT/P V = (1.66 mol) (0.0821 L·atm/mol·K)(413 K) (2.39 atm) V = 23.6 L

29. Example 2: Calculate (a) the # moles in, and (b) the mass of an 8.96 L sample of methane, CH 4, measured at standard conditions.  P = 1.00 atm  V = 8.96 L  n = ?  T = 273 K PV = nRT  n = PV/RT n = (1 atm)(8.96 L)/(0.0821 L·atm/mol·K)(273 K) n = 0.400 mol (a)

30. Example 2: Calculate (a) the # moles in, and (b) the mass of an 8.96 L sample of methane, CH 4, measured at standard conditions.  Or the easier way… (a)

31. Example 2: Calculate (a) the # moles in, and (b) the mass of an 8.96 L sample of methane, CH 4, measured at standard conditions.  Convert moles to grams… (b)

32. Example 3: Calculate the pressure exerted by 50.0 g ethane, C 2 H 6, in a 25.0 L container at 25 ºC?  P = ?  V = 25.0 L  n = (50.0 g)(1 mol / 30.08 g)  T = 25 °C + 273 = 298 K PV = nRT  P = nRT/V P= (1.66 mol)(0.0821 L·atm/mol·K)(298 K) (25.0 L) P = 1.62 atm

33. Warm up…. z0.0027500 z1000.00 z1045 z27590 z40730 z00.02470 z1.100 x 10 23 z Determine the number of sig. figs in each z Write each so that it contains 3 sig. figs.

34. zDALTON’S LAW OF PARTIAL PRESSURES

35. Dalton’s Law of Partial Pressures  In a mixture of gases each gas exerts the pressure it would exert if it occupied the volume alone.  The total pressure exerted by a mixture of gases is the sum of the partial pressures of the individual gases:  P total = P 1 + P 2 + P 3 + …

36. Example: If 100.0 mL of hydrogen gas, measured at 25  C and 3.00 atm, and 100.0 mL of oxygen, measured at 25  C and 2.00 atm, what sould be the pressure of the mixture of gases?  P total = P 1 + P 2 + P 3 + …  P T = 3.00 atm + 2.00 atm  P T = 5.00 atm Notice the two gases are measured at the same temp. and vol.

37. Vapor Pressure zWater evaporates! zWhen that water evaporates, the vapor has a pressure. zGases are often collected over water so the vapor pressure of water must be subtracted from the total pressure. zVapor pressure of water must be given or looked up.

38. Vapor Pressure of a Liquid  The pressure exerted by its gaseous molecules in equilibrium with the liquid; increases with temperature  In other words, as temperature increases vapor pressure increases

39. Vapor Pressure of a Liquid  P atm = P gas + P H 2 O  or  P gas = P atm - P H 2 O  You need this equation for the lab

40. Vapor Pressure of a Liquid (calculated using WATER DISPLACEMENT) Temp. (  C) v.p. of water (mm Hg) Temp. (  C) v.p. of water (mm Hg) 1815.482118.65 1916.482219.83 2017.542321.07

41. Example 1: A sample of hydrogen gas was collected by displacement of water at 25  C (vapor pressure of water at 25  C is 23.76 mm Hg). The atmospheric pressure was 748 mm Hg. What pressure would the dry hydrogen exert in the same conditions?  P H 2 = P atm - P H 2 O  P H 2 =748 mm Hg – 23.76 mm Hg  P H 2 = 724.24 mm Hg  P H 2  724 mm Hg

42. Example 2: A sample of oxygen gas was collected by displacement of water. The oxygen occupied 742 mL at 27  C (the vapor pressure of water at 27  C is 26.74 mm Hg). The atmospheric pressure was 753 mm Hg. What volume would the dry oxygen occupy at STP?  P O2 = P atm - P H2O  P O2 =753 mm Hg – 26.74 mm Hg  P O2 = 726 mm Hg  P 1 V 1 T 2 = P 2 V 2 T 1  V 2 = P 1 V 1 T 2 /P 2 T 1  V2 = (726 mm Hg)(742 mL)(273K)/(760 mm Hg)(300.K)  V 2 = 645 mL

43. The mole fraction Ratio of moles of the substance to the total moles present. (moles gas/ moles total) Symbol is Greek letter chi(  ) Mole fraction x total pressure = partial pressure

44. Graham’s Law of Diffusion & Effusion  Where,  Rate = rate of diffusion or effusion  MM=molar mass

45. WS: Graham’s Law z1. Under the same conditions of temperature and pressure, how many times faster will hydrogen effuse compared to carbon dioxide?

46. Answer to #1

47. z2. What is the relative rate of diffusion of NH 3 compared to He? Does NH 3 effuse faster or slower then He?

48. Extra Question zRank the following gases in terms of fastest to slowest effusion: Kr, He, Rn, N 2

49. ANSWER zThe lighter mass a gas has, the faster it will move. zThe heavier mass a gas has, the slower it will move. Fastest = He, N 2, Kr, Rn = Slowest