H02- Gas Laws-solutions - moczulski (ksm935) H02: Gas Laws...

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Unformatted text preview: moczulski (ksm935) H02: Gas Laws mccord (50960) 1 This print-out should have 23 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points A gas is enclosed in a 10.0 L tank at 1200 mm Hg pressure. Which of the following is a reasonable value for the pressure when the gas is pumped into a 5.00 L vessel? 1. 24 mm Hg 2. 0.042 mm Hg 3. 600 mm Hg 4. 2400 mm Hg correct Explanation: V 1 = 10.0 L V 2 = 5.0 L P 1 = 1200 mm Hg Boyles law relates the volume and pressure of a sample of gas: P 1 V 1 = P 2 V 2 P 2 = P 1 V 1 V 2 = (1200 mm Hg)(10 . 0 L) 5 L = 2400 mm Hg 002 10.0 points A sample of gas in a closed container at a temperature of 99 C and a pressure of 8 atm is heated to 306 C. What pressure does the gas exert at the higher temperature? Correct answer: 12 . 4516 atm. Explanation: T 1 = 99 C + 273 = 372 K P 1 = 8 atm T 2 = 306 C + 273 = 579 K P 2 = ? Applying the Gay-Lussac law, P 1 T 1 = P 2 T 2 P 2 = P 1 T 2 T 1 = (8 atm) (579 K) 372 K = 12 . 4516 atm 003 10.0 points If I have 44.8 liters of nitrogen gas at standard temperature and pressure, how much will it weigh? 1. 56 u 2. 28 g 3. 28 kg 4. 44.8 g 5. 56 g correct Explanation: P = 1 atm V = 44 . 8 L T = 273 K P V = n RT n = P V RT n = (1 atm)(44 . 8 L) ( . 08206 L atm K mol ) (273 K) 28 g 1 mol = 55 . 9941 g 004 10.0 points At 80.0 C and 12.0 Torr, the density of cam- phor vapor is 0 . 0829 g L 1 . What is the molar mass of camphor? 1. 20 . 3 g mol 1 2. 243 g mol 1 3. 3490 g mol 1 4. 152 g mol 1 correct 5. 34 . 5 g mol 1 Explanation: T = 80 C + 273.15 K = 353.15 K P = (12 Torr) 1 atm 760 Torr = 0 . 0157895 atm = 0 . 0829 g/L The ideal gas law is P V = n R T n V = P R T moczulski (ksm935) H02: Gas Laws mccord (50960) 2 with unit of measure mol/L on each side. Multiplying each by molar mass (MM) gives n V MM = P R T MM = , with units of g/L. MM = RT P = (0 . 0829 g / L) ( . 08206 L atm mol K ) . 0157895 atm (353 . 15 K) = 152 . 152 g / mol 005 10.0 points What is the density of nitrogen gas at STP? 1. 2.50 g/L 2. 0.500 g/L 3. 4.00 g/L 4. 0.625 g/L 5. 1.25 g/L correct Explanation: 006 (part 1 of 3) 10.0 points A chemist has synthesized a greenish-yellow gaseous compound that contains only chlorine and oxygen and has a density of 7.71 g/L at 36.0 degrees Celsius and 2188.8 mm Hg. What is the molar mass of the compound? 1. 25.8 g/mol 2. 67.9 g/mol correct 3. 109 g/mol 4. 86.9 g/mol 5. 51.5 g/mol Explanation: T = 36 C + 273 = 309 K P = 2188 . 8 mm Hg atm 760 mm Hg = 2 . 88 atm P V = n RT n V = P R T = (2 . 88 atm) (309 K)(0 . 08206 L atm molK ) = 0 . 1136 mol L MW = 7 . 71 g / L . 1136 mol L = 67 . 87 g / mol 007 (part 2 of 3) 10.0 points What is the molecular formula of the com- pound?...
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This note was uploaded on 10/01/2011 for the course CHEM 301 taught by Professor Wandelt during the Fall '08 term at University of Texas at Austin.

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H02- Gas Laws-solutions - moczulski (ksm935) H02: Gas Laws...

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