Thermodynamcs II____ 1. Of the following systems, which contains the most heat? a. 100 kg of water at 80C c. 600 kg of ice at 0C b. 250 kg of water at 40C d. Systems do not contain heat. 2. Carly places one end of a steel bar in a Bunsen flame and the other end in an ice cube. By what factor is the rate of heat flow changed when the bar's cross-sectional area is doubled? a. 2 c. 4.0 b. 1/2 d. 1/4 3. Dmitri places one end of a copper rod in a heat reservoir and the other end in a heat sink. By what factor is the rate of heat flow changed when the temperature difference between the reservoir and sink is tripled? a. 0.33 c. 3.0 b. 1/9 d. 9.0 4. The emissivity of an ideal reflector has which of the following values? a. 0 c. 100 b. 1 d. infinity 5. A 2.0-mol ideal gas system is maintained at a constant volume of 4.0 L. If 100 J of heat is added, what is the work done on the system? a. zero c. 6.7 J b. 5.0 J d. 20 J 6. A closed 2.0-L container holds 3.0 mol of an ideal gas. If 200 J of heat is added, what is the change in internal energy of the system? a. zero c. 150 J b. 100 J d. 200 J 7. A thermodynamic process that happens very quickly tends to be: a. isobaric. c. isovolumetric. b. isothermal. d. adiabatic. 8. A 10-kg piece of aluminum (which has a specific heat of 900 J/kgC) is warmed so that its temperature increases by 5.0 C. How much heat was transferred into it? a. 4.5 104 J c. 1.4 105 J b. 9.0 104 J d. 2.0 105 J 9. Marc attaches a falling 500-kg object with a rope through a pulley to a paddle wheel shaft. He places the system in a well-insulated tank holding 25 kg of water. When the object falls, it causes the paddle wheel to rotate and churn the water. If the object falls a vertical distance of 100 m at constant speed, what is the temperature change of the water? (1 kcal = 4 186 J, the specific heat of water is 4 186 J/kgC, and g = 9.8 m/s2) a. 19 600 C c. 4.7 C b. 4 700 C d. 0.8 C ____ ____ ____ ____ ____ ____ ____ ____ 1 28.34C d.1 105 2 . 1. 14.8 kg and the specific heat of water is 4 186 J/kgC. 1.) a. 590 W d. A solar heated house loses about 5. 163 kg c. 0. What mass of storage rock is needed to provide this amount of heat if it is brought up to initial temperature of 62C by the solar collectors and the house is maintained at 20C? (Specific heat of rock is 0. 44.00-m 2-area collector? (cw = 4 186 J/kgC) a. what would be its kinetic energy expressed in the unusual (for kinetic energy) units of calories? (1 cal = 4. How much mechanical energy is required to increase the temperature of 300 g of water (enough for 1 cup of coffee) from 20C to 95C? (1 cal = 4.) a. 9 400 W c. 9.0 kg of water when heated by an 800-W immersion heater for 10 min? (cw = 4 186 J/kgC) a. the solar radiation incident on the panels is 1 000 W/m2. 1 230 kg d. 51C d. What is the increase in temperature of 30.00-h period by a 4. 14 J ____ 11. 12 700 kg ____ 14. cw = 4 186 J/kgC) a.7C b.16C c. An inventor develops a stationary cycling device by which an individual. can convert all of the energy expended into heat for warming water.8 106 a.21 cal/gC. while pedaling. 216 kWh ____ 13. 330 kWh b.3C ____ 17. 1 770 kWh d. 56C c. What is the increase in water temperature at the bottom of the falls if all the initial potential energy goes into heating the water? (g = 9.8 m/s2. A solar heating system has a 25.0 kg of water in a 1.3C c. An inventor develops a stationary cycling device by which an individual. 3. 1 960 kWh c.____ 10.0 10 d.0 104 5 b. A swimming pool heater has to be able to raise the temperature of the 40 000 gallons of water in the pool by 10.186 J) c. can convert all of the energy expended into heat for warming water.69C b.4 107 cal through its outer surfaces on a typical 24-h winter day.04C ____ 15. 0. 14C ____ 16.186 J. What minimum power must be generated if 300 g water (enough for 1 cup of coffee) is to be heated in 10 min from 20C to 95C? (1 cal = 4. 3.0 C. 31 W ____ 12.0% conversion efficiency. 6 100 kg b. A waterfall is 145 m high. What is the temperature increase of 4. How many kilowatt-hours of energy are required? (One gallon of water has a mass of approximately 3. If a 1000-kg car was moving at 30 m/s. 0.4C d.186 J. while pedaling. 5 400 J b. the specific heat of water is 4 186 J/kgC) a. the specific heat of water is 4 186 J/kgC) a. 29C b. 22. 94 000 J c. 22 000 J d. 160 W b. 0C. 77.3C c.6 104 kg ____ 23.4C b.0 s to bore through the copper. 5. 1 kcal ____ 26.3 C ____ 19. +0.7 C d.7C ____ 22.8 kg of hot tea. Given cCu = 0. 4 320 cal b.003 0-kg lead bullet is traveling at a speed of 240 m/s when it embeds in a block of ice at 0C. 66. 1.0 W and takes 30. A 0. 1. +1. 2.50 g of water evaporates from the surface. what was the temperature of the kiln? a. 535C ____ 21.8 kg c.8 10 d.2 kg ____ 25.) a.0-kg person increase if all the energy in the bread were converted to heat? a.2 103 kg 4 kg b.86C d. Find the final equilibrium temperature when 10. A puddle holds 150 g of water.25C c. 2 160 cal 3 . what quantity of ice is melted? (Lf = 80 kcal/kg. A 120-g block of copper is taken from a kiln and quickly placed into a beaker of negligible heat capacity containing 300 g of water.43C b. The drill operates at 40. 820 cal b. 1.____ 18.00 cal/gC. 85. and its heat of vaporization is 50. 71. 620 cal c. The water temperature rises from 15C to 35C.0 g of milk at 10. 34. How many kg of ice. 1. How much heat energy is required to vaporize a 1.7C d. 720C b. find the copper's increase in temperature.00 cal/gC. the specific heat of lead = 0.0C is added to 160 g of coffee at 90. The heat of vaporization of water is 540 cal/g. a.4 kg b.47 102 kg c.6 kg d. (Assume the specific heats of coffee and milk are the same as water and neglect the heat capacity of the container.8 C c. initially at 80C. If specific heat of a person were 1. 360C d.33 105 J/kg. If all the heat generated goes into melting ice.18 C b.18 C ____ 24. initially at 0C. ccopper = 387 J/kgC.218 cal/gC. 2.0-g ice cube at 0C? The heat of fusion of ice is 80 cal/g.0 C b. 9 560 cal d. 500C c. 40. If all the energy from the drill heats the copper. 1. A piece of copper of mass 100 g is being drilled through with a 1/2" electric drill. 1.00 cal/gC = 4186 J/kgC a.00 kcal/kgC. A slice of bread contains about 100 kcal. 1.) cwater = 1.00C ____ 20.8 C d. 720 cal d. 1. If 0.03 kcal/kgC. 31.10 cal/gC. what is the approximate temperature change of the remaining water? (Lv = 540 cal/g) a. are required to bring the mixture to 10C? (Lf = 3.6 C c. and cwater = 1. 3. 13 700 cal c. 1. How much heat energy must be removed from 100 g of oxygen at 22C to liquefy it at 183C? (The specific heat of oxygen gas is 0. a. and cwater = 1. by how many C would the temperature of a 70. cw = 4 186 J/kgC) a. Iced tea is made by adding ice to 1. 27.9 cal/g. 0. and 1 kcal = 4 186 J) a. what is the ratio of the heat transferred by the aluminum to the heat transferred by the copper? a. A rod of each material is used as a heat conductor. The tungsten filament of a light bulb has an operating temperature of about 2 100 K. 8 J/s d. 100 W c.0 cm2.359 b.96 1030 W ____ 32. 1. 2 500 J/s d. about 68% ____ 35. If its emissivity remains constant. What is the equilibrium temperature of the hot asphalt. 1 300 J/s b. 62 W d. 105 W c.67 108 W/m2K4) a. 50 W ____ 29. The filament temperature of a light bulb is 2 000 K when the bulb delivers 40 W of power. 99C ____ 31. what power is delivered when the filament temperature is 2 500 K? a. 98 W b. If the temperature of the hotter end is reduced to 80C. 6. (Take e = 1. 3.95 1026 W c.68. what is the power output of the light bulb? ( = 5. 37 b. What is the rate of heat flow through this window? (Thermal conductivity for glass is 0.84 J/smC. heat is transferred at a rate of 16 J/s. If the rods have the same geometry and are used between the same temperature differences for the same time interval. A metal bar is used to conduct heat.78 ____ 30. When the temperature at one end is 100C and at the other is 20C. what will be the rate of heat transfer? a. and its emissivity is 0. 3.____ 27. The power then radiated by this object increases by how many percent? a. 630 J/s ____ 28. 9 J/s b. 12 J/s 4 . 75 W d. 84C d. 9.0 m 2.) a. 100% b.599 c. An object at 27C has its temperature increased to 37C. If the emitting area of the filament is 1. The thermal conductivity of aluminum is 238 J/smC and of copper is 397 J/smC. the sun delivers 1 000 W to each square meter of a blacktop road. 253 ____ 34. a.62 1028 W b. The temperature difference between the inside and outside surfaces of the pane is 15 C. and = 5.3 c. 60 W b.67 108 W/m2K4) . 0. 91C b. 5. At high noon. If the radius of the Sun is 7 108 m. 40 W ____ 33. 75C c.67 108 W/m2K4). What temperature increase is necessary to increase the power radiated from an object by a factor of 8? a. determine the power output of the sun. 14 d. 2.67 d. 8 K c. 0. 50 000 J/s c.17 1027 W d. The surface of the Sun has a temperature of about 5 800 K. a. 2 K d. assuming its emissivity e = 1? ( = 5. 4 J/s c. A windowpane is half a centimeter thick and has an area of 1. 55 m 3 although its pressure remains constant at 50 000 Pa.2 P0 d. 70 J c. going from an initial volume of 10 L to a final volume of 20 L. In an isobaric process 4. 30 J ____ 40. 3. 40% b.0 P0 a. 15% c.2 104 Pa c. 10 J d. If again it has ends at 100C and 20C. A 5-mol ideal gas system undergoes an adiabatic free expansion (a rapid expansion into a vacuum). 20 J c. 3. 200 000 J ____ 38. zero b.____ 36. A system is acted on by its surroundings in such a way that it receives 50 J of heat while simultaneously doing 20 J of work. 16 J/s b. A 4-mol ideal gas system undergoes an adiabatic process where it expands and does 20 J of work on its environment. 50% b. 60% ____ 44.0 P0 b. 5 J d. 50 J c. The bar is then stretched uniformly to twice its original length.16 P0 ____ 42.5 104 J of work is done on a quantity of gas while its volume changes from 2. 33% d. A metal bar is used to conduct heat.0 liters to 6. 6. at what rate will heat be transferred between it ends? a. 7 500 J b. +50 J ____ 43. How much work is done on the system during this adiabatic free expansion? a. What is its change in internal energy? a. What is the pressure during this process? a. 200 000 J d. 1. If the initial pressure is P0.0 104 Pa b. What is the efficiency of the engine? a. 60% c. 0. 50% d.1 104 Pa ____ 39. 9. When the temperature at one end is 100C and at the other is 20C. 7 500 J c. 32 J/s ____ 37.40 to 0. zero b. zero b.4 104 Pa d. A quantity of monatomic ideal gas expands adiabatically from a volume of 2.0 liters. 30 J d. The volume of an ideal gas changes from 0. What work is done on the system by its environment? a.1 m3. What is its net change in internal energy? a. A heat engine operating between a pair of hot and cold reservoirs with respective temperatures of 500 K and 200 K will have what maximum efficiency? a. 8 J/s d. 2. what is the final pressure? c. heat is transferred at a rate of 16 J/s. 4 J/s c. A heat engine exhausts 3 000 J of heat while performing 1 500 J of useful work. +20 J ____ 41.6 m 3 to 1. 4. 30% 5 . 3 000 W ____ 48. 1 810 MW d. what is the rate of heat input from the combustion phase? a. What is the maximum theoretical efficiency of this system? a. ____ 52. An 800-MW electric power plant has an efficiency of 30%. 1 200 MJ c. A gasoline engine with an efficiency of 30. 2 400 W d. d. 614 K b. 5 200 MW c. c. A heat engine receives 6 000 J of heat from its combustion process and loses 4 000 J through the exhaust and friction. 33% d. 1 800 W c. 457 K 6 . 3 620 MW b. 33% c. greater than 88% c. 2 000 W b. An electrical generating plant operates at a boiler temperature of 220C and exhausts the unused heat into a nearby river at 18C. what is the high-side temperature T1? a. Which of the following choices best describes the overall efficiency of the heat-to-work conversion in the plant (as a percentage)? a. 51%. 21% b.____ 45. 15%. The efficiency of a Carnot engine operating between 100C and 0C is most nearly: a.0% operates between a high temperature T1 and a low temperature T2 = 320 K. It loses its waste heat in large cooling towers. Approximately how much waste heat (in MJ) is discharged to the atmosphere per second? a. b. 64% d. Of the heat carried by the steam. 40% is converted to the mechanical energy of the spinning turbine. 67% ____ 49. 7%. 868 K d. An electrical generating plant operates at a boiler temperature of 220C and exhausts the unused heat into a nearby river at 19C. 1 900 MJ d. 50% b. What is its efficiency? a. What is the maximum theoretical efficiency of the plant? (0C = 273 K) a. 40% ____ 46. 67% b. 2 620 MW ____ 51. 560 MJ ____ 53. 41% ____ 50. An electrical power plant manages to send 88% of the heat produced in the burning of fossil fuel into the water-to-steam conversion. 1 070 K c. A turbine takes in 1 000-K steam and exhausts the steam at a temperature of 500 K. 32% d. 27%. 24% c. If this engine operates with Carnot efficiency. 61% c. If a heat engine has an efficiency of 30% and its power output is 600 W. less than 40% b. how much heat per second must be delivered to the boiler? (0C = 273 K) a. 40% d. If the generating plant has a power output of 800 megawatts (MW) and if the actual efficiency is 3/4 the theoretical efficiency. 800 MJ b. 73% ____ 47. 24.ID: A Thermodynamcs II Answer Section MULTIPLE CHOICE 1. 30. 5. 18. 32. 37. 27. 12. 29. 25. 16. 20. 21. 33. 13. 8. 17. D A C A A D D A C A C B C B C C D C C D A D B C B B B C A C A B B D D A A C B A 1 . 6. 3. 31. 23. 22. 2. 36. 39. 19. 15. 11. 28. 14. 38. 10. 26. 35. 9. 34. 4. 40. 7. 48. 45. 43. D C B A C A C C D D C B D 2 . 50. 46. 52. 42. 49. 47.ID: A 41. 53. 51. 44.