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Unformatted text preview: Cheung, Anthony – Exam 3 – Due: Nov 8 2006, 1:00 pm – Inst: McCord 1 This printout should have 22 questions. Multiplechoice questions may continue on the next column or page – find all choices before answering. The due time is Central time. 001 (part 1 of 1) 10 points Which would you expect to be most viscous? 1. C 8 H 18 at 50 ◦ C 2. C 4 H 8 at 30 ◦ C 3. C 4 H 8 at 50 ◦ C 4. C 8 H 18 at 30 ◦ C correct Explanation: 002 (part 1 of 1) 12 points What is the molar mass of a 0.710 g sample of gas that occupies a volume of 0.900 L at a pressure of 0.527 atm and a temperature of 49.0 ◦ C? Correct answer: 39 . 5726 g / mol. Explanation: m = 0 . 71 g P = 0 . 527 atm T = 49 . ◦ C + 273 . 15 = 322 . 15 K V = 0 . 9 L M = ? M = m RT P V = (0 . 71 g) ( . 08206 L · atm mol · K ) (322 . 15 K) (0 . 527 atm)(0 . 9 L) = 39 . 5726 g / mol 003 (part 1 of 1) 12 points How many atoms of argon occupy 1 mL if the temperature is 300 ◦ C and the pressure is 1 . 00 × 10 3 Torr? 1. 2 . 80 × 10 11 2. 2 . 44 × 10 19 3. 1 . 68 × 10 13 correct 4. 3 . 22 × 10 13 5. 1 . 28 × 10 16 Explanation: 004 (part 1 of 1) 10 points A sample of ideal gas occupies 10.0 L at 25 ◦ C. If the temperature is increased to 125 ◦ C while maintaining the same pressure, the volume will be 1. 1201 L. 2. 13.4 L. correct 3. 7.5 L. 4. 50 L. Explanation: T 1 = 25 ◦ C + 273 = 298 K V 1 = 10.0 L T 2 = 125 ◦ C + 273 = 398 K Charles’ law relates the volume and abso lute (Kelvin) temperature of a sample of gas: V 1 T 1 = V 2 T 2 V 2 = V 1 T 2 T 1 = (10 . 0 L)(398 K) 298 K = 13 . 4 L 005 (part 1 of 1) 10 points A sample of a gas occupies 3080 milliliters at 20.0 ◦ C and 4549 torr. What volume would it occupy at the same temperature and 263 torr? Correct answer: 53273 . 5 mL. Explanation: P 1 = 4549 torr P 2 = 263 torr V 1 = 3080 mL Applying Boyle’s Law, P 1 V 1 = P 2 V 2 V 2 = P 1 V 1 P 2 = (4549 torr)(3080 mL) 263 torr = 53273 . 5 mL 006 (part 1 of 1) 10 points What volume of hydrogen gas (at STP) would be required to produce 1.00 mole of HCl? Cheung, Anthony – Exam 3 – Due: Nov 8 2006, 1:00 pm – Inst: McCord 2 H 2 (g) + Cl 2 (g) → 2 HCl(g) 1. 5.3 L 2. 22.4 L 3. 11.2 L correct 4. 44.8 L 5. 6.6 L Explanation: n 1 = 1 mol n 2 = 0.5 mol V 1 = 22.4 L 1 mole of an ideal gas at STP (T = 0 ◦ C = 273 . 15 K , P = 1 atm) has a volume of 22 . 4 L. If T and P are constant the ideal gas law reduces to V 1 V 2 =...
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This note was uploaded on 11/11/2010 for the course CH 301 taught by Professor Fakhreddine/lyon during the Fall '07 term at University of Texas at Austin.
 Fall '07
 Fakhreddine/Lyon
 Chemistry

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