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H02- Gas Laws-solutions

# H02- Gas Laws-solutions - moczulski(ksm935 H02 Gas Laws...

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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 10.0points 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 Boyle’s 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 10.0points 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 10.0points 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 R T n = P V R T n = (1 atm)(44 . 8 L) ( 0 . 08206 L · atm K · mol ) (273 K) · 28 g 1 mol = 55 . 9941 g 004 10.0points 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 ρ = 0 . 0829 g/L The ideal gas law is P V = n R T n V = P R T

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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 = ρ , with units of g/L. MM = ρ R T P = (0 . 0829 g / L) ( 0 . 08206 L · atm mol · K ) 0 . 0157895 atm × (353 . 15 K) = 152 . 152 g / mol 005 10.0points 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(part1of3)10.0points 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 R T n V = P R T = (2 . 88 atm) (309 K)(0 . 08206 L · atm molK ) = 0 . 1136 mol L MW = 7 . 71 g / L 0 . 1136 mol L = 67 . 87 g / mol 007(part2of3)10.0points What is the molecular formula of the com- pound? 1. ClO 4 2. ClO 3 3. ClO 4. ClO 2 correct 5. ClO 5 Explanation: MW ClO 2 = (35 . 5) + 2(16) = 67 . 5 g / mol 008(part3of3)10.0points How many moles of this gaseous compound are there in 15 L at STP?
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H02- Gas Laws-solutions - moczulski(ksm935 H02 Gas Laws...

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