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Unformatted text preview: romasko (qrr58) – Homework 7 – sutcliffe – (50985) 1 This printout should have 20 questions. Multiplechoice questions may continue on the next column or page – find all choices before answering. 001 10.0 points A gas has a pressure of 5 . 87973 atm when its volume is 3 . 45 L. What will the pressure be when the volume is changed to 1 . 09855 L, assuming constant temperature? Express the final pressure in torr. Correct answer: 14033 . 6 torr. Explanation: V 1 = 3 . 45 L V 2 = 1 . 09855 L P 1 = 5 . 87973 atm P 2 = ? By Boyle’s law, P 1 V 1 = P 2 V 2 P 2 = P 1 V 1 V 2 = (5 . 87973 atm) (3 . 45 L) 1 . 09855 L · parenleftbigg 760 torr atm parenrightbigg = 14033 . 6 torr 002 10.0 points For an ideal gas, pressure has what relation ship to volume provided only pressure and volume are allowed to change? 1. proportional 2. unrelated 3. inversely proportional correct 4. equal Explanation: Boyle’s law, P = k 1 V or P ∝ 1 V , relates the volume and pressure of a sample of gas at constant temperature. This relationship is an inverse proportionality. 003 10.0 points Which of the following is a true statement about a fixed amount of ideal gas at constant pressure? 1. If a sample of gas is heated from 100 ◦ C to 200 ◦ C, the volume will decrease by a factor of two. 2. If a sample of gas is heated from 0 ◦ C to 273 ◦ C, the volume will double. correct 3. If a sample of gas is cooled from 400 ◦ C to 200 ◦ C, the volume will decrease by a factor of two. Explanation: Volume is directly proportional to temper ature expressed on the Kelvin scale. ◦ C → 270 ◦ C: ◦ C + 273 = 273 K; 273 ◦ C + 273 = 546 K. The Kelvin temperature changes by a factor of 2 parenleftbigg i . e ., 546 273 parenrightbigg , so the volume would also double. 400 ◦ C → 200 ◦ C: 400 ◦ C + 273 = 673 K; 200 ◦ C + 273 = 473 K. The Kelvin temperature changes by a fac tor of 0.70 parenleftbigg i . e ., 473 546 parenrightbigg , so the volume would change by a factor of 0.70. A temperature increase from 100 ◦ C to 200 ◦ C would cause the volume to increase, not decrease, so this response must be incor rect. 004 10.0 points A sample of a gas occupies 1580 mL at 26 . 8 ◦ C and 740 torr. What volume would it occupy at the same pressure and 175 ◦ C? Correct answer: 2361 mL. Explanation: T 1 = 26 . 8 ◦ C + 273 = 299 . 8 K V 1 = 1580 mL T 2 = 175 ◦ C + 273 = 448 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 = (1580 mL) (448 K) 299 . 8 K romasko (qrr58) – Homework 7 – sutcliffe – (50985) 2 = 2361 mL 005 10.0 points A 764 mL gas sample at STP is compressed to a volume of 177 mL, and the temperature is increased to 30 ◦ C. What is the new pressure of the gas in Pa?...
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This note was uploaded on 06/07/2011 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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