Homework 7-solutions

Homework 7-solutions - dewitt(aad777 Homework 7...

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dewitt (aad777) – Homework 7 – sutclife – (52380) 1 This print-out should have 20 questions. Multiple-choice questions may continue on the next column or page – Fnd all choices be±ore answering. 001 10.0 points A gas has a pressure o± 6 . 69501 atm when its volume is 2 . 42 L. What will the pressure be when the volume is changed to 1 . 76592 L, assuming constant temperature? Express the Fnal pressure in torr. Correct answer: 6972 . 83 torr. Explanation: V 1 = 2 . 42 L V 2 = 1 . 76592 L P 1 = 6 . 69501 atm P 2 = ? By Boyle’s law, P 1 V 1 = P 2 V 2 P 2 = P 1 V 1 V 2 = (6 . 69501 atm) (2 . 42 L) 1 . 76592 L · p 760 torr atm P = 6972 . 83 torr 002 10.0 points ²or an ideal gas, pressure has what relation- ship to volume provided only pressure and volume are allowed to change? 1. unrelated 2. inversely proportional correct 3. equal 4. proportional Explanation: Boyle’s law, P = k 1 V or P 1 V , relates the volume and pressure o± a sample o± gas at constant temperature. This relationship is an inverse proportionality. 003 10.0 points Which o± the ±ollowing is a true statement about a Fxed amount o± ideal gas at constant pressure? 1. I± a sample o± gas is cooled ±rom 400 C to 200 C, the volume will decrease by a ±actor o± two. 2. I± a sample o± gas is heated ±rom 100 C to 200 C, the volume will decrease by a ±actor o± two. 3. I± a sample o± gas is heated ±rom 0 C to 273 C, the volume will double. correct Explanation: Volume is directly proportional to temper- ature expressed on the Kelvin scale. 0 C 270 C: 0 C + 273 = 273 K; 273 C + 273 = 546 K. The Kelvin temperature changes by a ±actor o± 2 p i . e ., 546 273 P , 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 ±ac- tor o± 0.70 p i . e ., 473 546 P , so the volume would change by a ±actor o± 0.70. A temperature increase ±rom 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 o± a gas occupies 1070 mL at 87 . 4 C and 740 torr. What volume would it occupy at the same pressure and 163 C? Correct answer: 1294 . 5 mL. Explanation: T 1 = 87 . 4 C + 273 = 360 . 4 K V 1 = 1070 mL T 2 = 163 C + 273 = 436 K Charles’ law relates the volume and abso- lute (Kelvin) temperature o± a sample o± gas: V 1 T 1 = V 2 T 2 V 2 = V 1 T 2 T 1 = (1070 mL) (436 K) 360 . 4 K
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dewitt (aad777) – Homework 7 – sutclife – (52380) 2 = 1294 . 5 mL 005 10.0 points A 743 mL gas sample at STP is compressed to a volume oF 124 mL, and the temperature is increased to 22 C. What is the new pressure oF the gas in Pa? Correct answer: 6 . 56059 × 10 5 Pa. Explanation: V 1 = 743 mL V 2 = 124 mL T 1 = 0 C + 273 = 273 K P 1 = 1 atm T 2 = 22 C + 273 = 295 K P 2 = ?
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Homework 7-solutions - dewitt(aad777 Homework 7...

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