EF 152 Exam 3 - Fall, 2016 Page 1 Copy 223

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1 EF 152 Exam 3 - Fall, 2016 Page 1 Copy 223 Instructions Do not open the exam until instructed to do so. Do not leave if there is less than 5 minutes to go in the exam. When time is called, immediately stop writing, remain seated, and pass your exam to the center aisle. Working after time is called results in an automatic deduction. Turn your equation sheets in with your exam. Guidelines Assume 3 significant figures for all given numbers unless otherwise stated Show all of your work no work, no credit Write your final answer in the box provided Include units for all answers Other: c ice=0.5 cal/(g- C) p atm=14.7psi diatomic ideal gas: C p =29.1J/(mol-K) C v =20.8 J/(mol-K)

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3 EF 152 Exam 3 - Fall, 2016 Page 3 Copy 223 Name: Section: 1. Write your name and section above. Specify your EXAM ID below. Use 000 if you don t know your exam ID Digit #1 Digit #2 Digit #3 4. (2 pt) An object s material has a negative coefficient of thermal expansion. How would the volume of an object change when it cools? Impossible to have a negative value No change Expands Contracts 5. (2 pt) What takes the least amount of energy? Raise 1g of ice 1 C Raise 1g of water 1 C Melt 1g of ice at 0 C Boil 1g of ice at 100 C 6. (2 pt) 3.1 liters is how many m (2 pt) How would you calculate DQ for an isothermal process? V 0 nrt ln 2 nc p T nc T V v p V p V A A B B 8. (2 pt) Which of the following processes has DQ = 0? Adiabatic Isobaric Isochoric Isothermal 9. (2 pt) Which process will have positive net work? ADBA ABDA CBDC ADCBA

4 EF 152 Exam 3 - Fall, 2016 Page 4 Copy (2 pt) When does a heat engine do positive work? Constant Volume Volume Increase Volume Decrease 11. (2 pt) What is 212 F equivalent to? 212 K 312 K 273 K 373 K 12. (2 pt) What is the approximate volume of 1 mole of an ideal gas at STP? 1 m 3 1 cm 3 1 ft 3 1 in (2 pt) A gage pressure is reported as 42 psi. What is the corresponding absolute pressure? 42 psi 0 psi 56.7 psi 27.3 psi 14. (2 pt) An ideal gas with pressure P and volume V doubles in volume at constant temperature. What is the new pressure? ½ P P 2P 4P 15. (2 pt) An ideal gas with pressure P and temperature T doubles in temperature at constant volume. What is the new pressure ½ P P 2P 4P 16. (2 pt) Which weighs more, a mole of nitrogen (N 2) gas or a mole of oxygen (O 2) gas? Atomic mass: N=14, O=16. Same O 2 N (2pt) You put 1 kg of ice a 0 C together with 1 kg of water at 40 C. What is the final temperature T? T = 0 C 0 C < T < 20 C T = 20 C 20 C < T < 40 C 18. (2pt) Two equal mass liquids, initially at the same temperature, have equal amounts of heat added to them. After the heat is added, they have different temperatures. Which liquid has the lower specific heat value? The cooler one The hotter one Both the same

5 EF 152 Exam 3 - Fall, 2016 Page 5 Copy (10 pt) A cooler s walls, floor, and lid are all made of two layers of plastic with a layer of styrofoam in the middle. The total surface area of the cooler is 11.5 ft 2. The inside temperature of the cooler is 5 F and the outside temperature is 86 F. How much heat is lost from the cooler in 2.5 hrs? R plastic (one layer) = 0.8 (hr- F-ft 2 ) / BTU R styrofoam = 4.2 (hr- F-ft 2 ) / BTU 20. (10 pt) A 2.2m long wire (E = 175 GPa) has a coefficient of linear expansion of 1.07x10-5 m/(m- C). Determine the stress in the wire if it is fixed (stretched tight, no tension) at 32 C and then allowed to cool to -10 C. 21. (10 pt) The temperatures in two EF TA offices are 85 C and 80 C. The TAs want to use this difference to generate power. If they can build an ideal (Carnot) heat engine, and can extract heat from the hot office at a rate of 330 W, how much power can they generate?

6 EF 152 Exam 3 - Fall, 2016 Page 6 Copy (20 pt) 25% of the heat released from burning fuel in a campstove actually goes to heating a pot and its contents. You start with 0.7 kg of ice at -15 C, 1.7 kg of water at 24 C, and a 0.35 kg aluminum pot at 31 C. The ice and water are put into the pot and the system is heated to 80 C. The specific heat of aluminum is 0.22 cal/g- C. One gram of fuel produces J when it is burned. How much fuel is burned? 23. (20 pt) 0.7 m 3 of an ideal diatomic gas is initially at atmospheric pressure. A-B: The gas is heated at constant volume. B-C: The gas is allowed to expand isothermally to 2.1 m 3. C-A: The gas is returned to the initial volume at constant pressure. Draw the p-v graph and label the states (5 pt) Calculate the net work done during the cycle. p V