# exam1 - Version 267 Exam 1 mccord(50960 This print-out...

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Version 267 – Exam 1 – mccord – (50960) 1 This print-out should have 26 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0points Absolute zero (0 K) is the temperature at which 1. None of these 2. a graph of P versus 1 V intersects the 1 V axis. 3. gaseous helium liquefies. 4. the straight line graph of V versus T intersects the T axis. correct 5. a graph of V versus 1 P intersects the 1 P axis. Explanation: A graph of V vs. T is a straight line. This line intersects the temperature axis at - 273 C, at which is 0 K or absolute zero. 002 10.0points For a sample of gas held at constant temper- ature, a plot of volume versus pressure is a straight line. 1. False correct 2. True Explanation: Volume of a gas sample is inversely propor- tional to pressure. The plot of V versus P is not a straight line, but a hyperbola. 003 10.0points Which of the following is most likely to devi- ate from ideal behavior? 1. a gas at high pressure correct 2. a noble gas 3. a gas at high temperature 4. a gas at low density Explanation: Deviations from ideality occur due to molecular attractions or repulsions. More attractions or repulsions can occur when the molecules are closer together. Low pressure, high volume, and low density all correspond to molecules being far apart. Low temper- ature often corresponds to molecules being close together. It also corresponds to low ki- netic energy which allows molecules to ‘stick together’ easier. High pressures also corre- spond to molecules being close together. 004 10.0points The following plot is for an ideal gas. Identify what state function(s) could be represented by x for this plot. x V 1. T , or n correct 2. T only 3. P , or n 4. P , or T 5. n only 6. P only 7. P , T , or n Explanation: The plot shows a direct proportionality (a straight line). According to the Ideal Gas Law, volume ( V ) is directly proportional to temperature ( T ) and the number of moles ( n ) of a gas. Volume is inversely proportional to pressure. 005 10.0points

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Version 267 – Exam 1 – mccord – (50960) 2 The graph shows the Maxwell distribution plots for a given gas at three different temper- atures. 0 500 1000 1500 2000 velocity (m/s) relative number of molecules A B C Which plot corresponds to the highest tem- perature? 1. B 2. C correct 3. Can not be determined from this type of plot. 4. A Explanation: The higher the temperature, the broader the range of velocity distributions and the higher the average velocity. So curve C matches that criteria. 006 10.0points A sample of argon gas occupies a volume of 364 mL at 15 C. What volume will the gas occupy at 61 . 2605 C, assuming constant pressure? 1. 422.468 2. 335.654 3. 457.743 4. 358.665 5. 403.147 6. 303.919 7. 376.77 8. 412.043 9. 282.764 10. 220.333 Correct answer: 422 . 468 mL. Explanation: V 1 = 364 mL V 2 = ? T 1 = 15 C = 288 K T 2 = 61 . 2605 C = 334 . 26 K By Charles’ law, V 1 T 1 = V 2 T 2 V 2 = V 1 T 2 T 1 = (364 mL)(334 . 26 K) 288 K = 422 . 468 mL 007 10.0points The Scoville scale is a measurement of the spicy heat of a chili pepper. The number of Scoville heat units (SHU) is really an indica- tor of how much capsaicin is present in the chili. So could the spicy heat of a pepper be considered a state function?
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