General E grp E geo formula Hybridizaton and mol bond angle geo shape AB2 2 Linear Sp 180 Linear AB3 3 Trigonal planar Sp2 120 AB2U 3 Trigonal planar Sp2 120 Trigonal planar Bent angular AB4 4 Tetrahedral Sp3 109 5 Tetrahedral AB3U 4 Tetrahedral Sp3 109 5 AB2U2 4 Tetrahedral Sp3 109 5 Trigonal pyramidal Angular bent Sigma bonds Pi bonds Clicker Q How many bonds are in this molecule 11 Clicker Q How many bonds 1 Ch 12 Gases and the kinetic molecular theory End of chapter problems partial list 5 6 12 14 18 20 23 25 29 31 45 48 51 58 66 67 68 72 74 80 Comparison of Solids Liquids and Gases The density of gases is much less than that of solids or liquids Densities g mL Solid Liquid Gas H2O 0 917 0 998 0 000588 CCl4 1 70 1 59 0 00503 Gas molecules must be very far apart compared to liquids and solids 4 Composition of the Atmosphere and Some Common Properties of Gases Composition of Dry Air Gas N2 by Volume 78 09 O2 20 94 Ar CO2 0 93 0 03 He Ne Kr Xe CH4 0 002 0 00015 H2 0 00005 5 Pressure Pressure is force per unit area lb in2 N m2 Atmospheric pressure is measured using a barometer Definitions of standard pressure KNOW not on resources 76 cm Hg 760 mm Hg 760 torr 1 atmosphere 101 3 kPa Hg density 13 6 g mL 6 Conversions Boyle s Law The Volume Pressure Relationship At a given T the product of the pressure and volume of a definite mass of gas is constant PV k constant n T T always in Kelvin http www grc nasa gov WWW k 12 airplane aboyle html good example http www youtube com watch v t8wFIMbMJvs feature related scuba dive example http www rkm com au animations GAS volumepressure html ok example 9 At 25oC a sample of He has a volume of 4 00 x 102 mL under a pressure of 7 60 x 102 torr What volume would it occupy under a pressure of 2 00 atm at the same T Think what it should be first V1 400 mL P1 760 torr 1 atm 760 torr 1 atm P2 2 00 atm V2 T constant 10 Boyle s Law The Volume Pressure Relationship Notice that in Boyle s law we can use any pressure or volume units as long as we consistently use the same units for both P1 and P2 or V1 and V2 Use your intuition to help you decide if the volume will go up or down as the pressure is changed and vice versa 11 Clicker Q What volume will 2 50 l of a gas occupy if the pressure is changed from 760 mm Hg to 630 mm Hg 250 L 760 mm 630 mm x x 3 02 L Charles Law The Volume Temperature Relationship Charles s law states that the volume of a gas is directly proportional to the absolute temperature at constant pressure http www grc nasa gov WWW k 12 airplane aglussac html good one http group chem iastate edu Greenbowe sections projectfolder flashfiles gaslaw boyles law graph htm l cool one can change volume http www nclark net GasLaws good website with lots of examples Gas laws must use the Kelvin scale to be correct V kt V T k V1 T1 V2 T2 Relationship between Kelvin and centigrade K o C 273 13 Charles Law The Volume Temperature Relationship absolute zero 273 15 0 C 14 Charles Law The Volume Temperature Relationship A sample of hydrogen H2 occupies 1 00 x 102 mL at 25 0oC and 1 00 atm What volume would it occupy at 50 0oC under the same pressure 108 mL V1 1 00 x 102 mL T1 298 K P 1 atm V2 T2 323 K 1 00 X 102 mL 298 K V2 323K V2 108 mL Temperature increase expect volume to increase 15 If 20 0 l of oxygen are cooled from 100 C to 0 C what is the new volume 20 0L 373K 273K V2 V2 14 6 L Clicker Q 3 00 l of hydrogen at 20 C are allowed to warm to a room temperature of 27 C What is the volume at RT if the P remains constant 3 00 L 253 K V2 300 V2 3 56 L Standard Temperature and Pressure Standard temperature and pressure is given the symbol STP It is a reference point for some gas calculations Standard P 1 00000 atm or 101 3 kPa Standard T 273 15 K or 0 00oC KNOW 18 The Combined Gas Law Equation Boyle s and Charles Laws combined into one statement is called the combined gas law equation Useful when the V T and P of a gas are changing http www mhhe com physsci chemistry essentialchemistry flash ga sesv6 swf awesome site for all gas laws Boyle s Law P1V1 P2 V2 Charles Law V1 V2 T1 T2 For a given sample of gas The combined gas law is PV P1 V1 P2 V2 k T T1 T2 19 The Combined Gas Law Equation A sample of nitrogen gas N2 occupies 7 50 x 102 mL at 75 00C under a pressure of 8 10 x 102 torr What volume would it occupy at STP V1 750 mL T1 348 K P 810 torr V2 T2 273 K P2 760 torr 810 torr 750 mL 348 760x 273 V2 627 mL 20 A sample of methane CH4 occupies 2 60 x 102 mL at 32oC under a pressure of 0 500 atm At what temperature would it occupy 5 00 x 102 mL under a pressure of 1 20 x 103 torr V1 260 mL T1 305 K P1 380 torr V2 500 mL T2 P2 1200 torr 380torr 260mL 305K 1200 torr 500mL x X 1 85 x 103 K 21 Clicker Q Given 20 0 l of ammonia gas at 5 C and 730 torr calculate the volume at 50 C and 800 torr V1 20 L T1 278 K P1 730 torr V2 x T2 323 K P2 800 torr 730 20 278 800 x 323 V2 21 2 L Avogadro s Law and the Standard Molar Volume http www mhhe com physsci chemistry essentialchemistry flash gases v6 swf awesome site for all gas laws 23 Avogadro s Law and the Standard Molar Volume Avogadro s Law states that at the same temperature and pressure equal volumes of two gases contain the same number of molecules or moles of gas If we set the temperature and pressure for any gas to be STP then one mole of that gas has a volume called the standard molar volume The standard molar volume is 22 4 L at STP This is another way to measure moles For gases the volume is proportional to the number of moles 11 2 L of a gas at STP 0 500 mole 44 8 L moles 24 One mole of a gas occupies 36 5 L and its density is 1 36 …