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Unit 1 Exam Multiple Choice Portion-solutions

# Unit 1 Exam Multiple Choice Portion-solutions - Version 316...

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Version 316 – Unit 1 Exam Multiple Choice Portion – vanden bout – (50985) 1 This print-out should have 24 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 4.0points The ideal gas law does not model actual gas behavior in the limit of high pressure because it fails to take into account 1. that the particles are smaller at high pres- sure. 2. the interactions between the gas particles. correct 3. that the pressure depends on the number of gas particles. 4. the kinetic energy of the gas particles. 5. the distribution of velocities of the gas particles. Explanation: The ideal gas law fails at high pressure as the interactions between the gas molecules becomes more important. Kinetic molecular theory arrives at the ideal gas law and it takes into account both the KE and the distribution of velocities. The molecular size does not vary to any significant extent with pressure. The pressure depends on the number of molecules in the ideal gas law. 002 4.0points Standard Ambient Temperature and Pressure (SATP) [not to be confused with STP] is de- fined as a temperature of 25 C and a pressure of 1 bar. What is the molar volume of an ideal gas at SATP? 1. 1.000 L mol 1 2. 24.47 L mol 1 3. 24.79 L mol 1 correct 4. 0.04461 L mol 1 5. 22.41 L mol 1 Explanation: For this you are looking for the volume of one mole of gas at 25 C and 1 bar. V m = V n = RT P Plugging in the values gives V m = RT P = (0 . 08314 L bar K 1 mol 1 )(298 . 15 K) 1 bar V m = 24 . 79 L mol 1 003 4.0points If more points are awarded on this assign- ment, would you like them added to your score? 1. YES, I would like the points and the higher score. correct 2. NO, leave my score alone, I prefer the lower score Explanation: This should be a no-brainer. Most students want higher scores. If you picked yes, you got credit for the question and you got the extra points you asked for (if they were granted by your instructor). If you answered NO, you also got what you wanted... no points awarded. 004 4.0points An ideal gas initially has a volume of 10 L at a temperature of 300K and a pressure of 4 atm. It undergoes a process which results in the temperature being 600 K and the volume being 20 L. What is the final pressure? 1. 1 atm 2. 4 atm correct

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Version 316 – Unit 1 Exam Multiple Choice Portion – vanden bout – (50985) 2 3. 8 atm 4. 2 atm 5. 16 atm Explanation: The gas doubles in temperature which would result in the pressure doubling. How- ever, the volume also doubles which would reduce the pressure by 2. So the pressure doesn’t change. P 1 V 1 T 1 = P 2 V 2 T 2 P 2 = P 1 V 1 T 2 V 2 T 1 = 4 · 10 · 600 20 · 300 = 4 atm 005 4.0points What mass of KNO 3 would have to be decom- posed to produce 21.1 L of oxygen measured at STP? 2KNO 3(s) -→ 2KNO 2(s) + O 2(g) 1. 95.2 g 2. 190 g correct 3. 202 g 4. 130 g Explanation: .
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