Chemical Engineering Thermodynamics Review

GERAF REVIEW NOTES Prepared by: Gerry Lou Quiles, CSA-B

Chemical Engineering Thermodynamics 1 1.

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Consider a fish swimming 5 m below the free surface of water. The increase in the pressure exerted on the fish when it dives to a depth of 45 m below the free surface isa. 392 Pa b. 9800 Pa c. 50,000 Pa d. 392,000 Pa An apple loses 4.5 kJ of heat as it cools per °C drop in its temperature. The amount of heat loss from the apple per °F drop in its temperature isa. 1.25 kJ b. 2.50 kJ c. 5.0 kJ d. 8.1 kJ A 2-kW electric resistance heater in a room is turned on and kept on for 30 min. The amount of energy transferred to the room by the heater isa. 1 kJ b. 60 kJ c. 1800 kJ d. 3600 kJ In a hot summer day, the air in a well-sealed room is circulated by a 0.50-hp (shaft) fan driven by a 65% efficient motor. (Note that the motor delivers 0.50 hp of net shaft power to the fan). The rate of energy supply from the fan-motor assembly to the room is a. 0.769 kJ/s b. 0.325 kJ/s c. 0.574 kJ/s d. 0.373 kJ/s 3 A fan is to accelerate quiescent air to a velocity to 12 m/s at a rate of 3 m /s. If the density of air 3 is 1.15 kg/m , the minimum power that must be supplied to the fan isa. 248 W b. 72 W c. 497 W d. 216 W The elevator of a large building is to raise a net mass of 400 kg at a constant speed of 12 m/s using an electric motor. Minimum power rating of the motor should bea. 0 kW b. 4.8 kW c. 47 kW d. 12 kW Electric power is to be generated in a hydroelectric power plant that receives water at a rate of 3 70 m /s from an elevation of 65 m using a turbine–generator with an efficiency of 85 percent. When frictional losses in piping are disregarded, the electric power output of this plant isa. 3.9 MW b. 38 MW c. 45 MW d. 53 MW A 75 hp (shaft) compressor in a facility that operates at full load for 2500 hours a year is powered by an electric motor that has an efficiency of 88 percent. If the unit cost of electricity is P0.06/kWh, the annual electricity cost of this compressor isa. P 7382 b. P9900 c. P12,780 d. P9536 Ten centimeter high and twenty centimeter wide circuit board houses on its surface 100 closely spaced chips, each generating heat at a rate of 0.08 W and transferring it by convection to the surrounding air at 40°C. Heat transfer from the back surface of the board is negligible. If the 2 convection heat transfer coefficient on the surface of the board is 10 W/m °C and radiation heat transfer is negligible, the average surface temperature of the chips isa. 80°C b. 54°C c. 41°C d. 72°C If two objects are in thermal equilibrium with each othera. they cannot be moving b. they cannot be undergoing an elastic collision c. they cannot have different pressures d. they cannot be at different temperatures A "closed system" is also known asa. Control mass b. isolated system c. control volume d. control boundary Properties that are independent of the size of the system, such as temperature, pressure, and the density are calleda. intensive properties c. extensive properties b. extrinsive properties d. extrinsic properties A H-S diagram is also known asa. Argand diagram b. Euler diagram c. Mollier diagram d. Grolier diagram The condition in which there is no change in pressure at any point of the system with time. a. Thermal equilibrium c. mechanical equilibrium b. Phase equilibrium d. chemical equilibrium

15. A process during which, the specific volume V remains constant is calleda. Isometric b. isovolumetric c. isochoric d. all of these 16. Who wrote the first thermodynamics textbook in 1859? a. Lord Kelvin b. William Rankine c. Thomas Young d. Rudolph Clausius 17. The area under the process curve on a P-V diagram represents the boundarya. Temperature b. pressure c. energy d. work 18. A device that increases the pressure of a fluid by slowing it down is calleda. Noozle b. diffuser c. manometer d. heat exchanger 19. A rigid tank contains 6 kg of an ideal gas at 3 atm and 40°C. Now a valve is opened, and half of mass of the gas is allowed to escape. If the final pressure in the tank is 2.2 atm, the final temperature in the tank isa. 186°C b. 59°C c. -43°C d. 20°C 20. Water is boiling at 1 atm pressure in a stainless steel pan on an electric range. It is observed that 2 kg of liquid water evaporates in 30 minutes. The rate of heat transfer to the water isa. 2.51 kW b. 2.32 kW c. 2.97 kW d. 0.47 kW 3 21. A rigid 3-m rigid vessel contains steam at 10 MPa and 500°C. The mass of the steam isa. 3.0 kg b. 19 kg c. 84 kg d. 31 kg 22. A certain humidifier operates by raising water to the boiling point and then evaporating it. Every minute 30 g of water at 20 °C are added to replace the 30 g that are evaporated. The heat of fusion of water is 333 kJ/kg, the heat of vaporization is 2256 kJ/kg, and the specific heat is 4190 J/kg · K. How many joules of energy per minute does this humidifier require? 4 4 4 5 a. 3.0 × 10 b. 8.8 × 10 c. 7.8 × 10 d. 1.1 × 10 23. A system undergoes an adiabatic process in which its internal energy increases by 20 J. Which of the following statements is true? a. 20 J of work was done on the system c. the system received 20 J of energy as heat b. 20 J of work was done by the system d. the system lost 20 J of energy as heat 24. A frictionless piston-cylinder device and a rigid tank contain 2 kmol of an ideal gas at the same temperature, pressure and volume. Now heat is transferred, and the temperature of both systems is raised by 10°C. The amount of extra heat that must be supplied to the gas in the cylinder that is maintained at constant pressure isa. 0 kJ b. 42 kJ c. 83 kJ d. 166 kJ 3 25. A 3-m rigid tank contains nitrogen gas at 500 kPa and 300 K. Now heat is transferred to the nitrogen in the tank and the pressure of nitrogen rises to 800 kPa. The work done during this process isa. 500 kJ b. 1500 kJ c. 0 kJ d. 900 kJ 26. ChE GATE PROBLEM 2011. One mole of methane is contained in a leak proof piston cylinder assembly at 8 bar and 1000 K. The gas undergoes isothermal expansion to 4 bar under reversible conditions. Methane can be considered as an ideal gas under these conditions. The heat transferred in kJ during the process isa. 11.52 b. 5.76 c. 4.15 d. 2.38 27. Equations of state for a single component can be any of the following, except: a. the ideal gas law, PV= RT b. the ideal gas law modified by insertion of a compressibility factor, PV = ZRT. c. any relationship interrelating 3 or more state functions. d. a mathematical expression defining a path between states. 28. The state of a thermodynamic system is always defined by itsa. absolute temperature b. process c. properties d. temperature and pressure 29. Mathematically, a thermodynamic property is which of the following? a. a point function c. an inexact differential b. a path function d. discontinuous O 30. PIChE National Quiz Bee 2007. Three moles of an ideal gas at 1 atm and 20 C are heated at O -2 constant pressure until the final temperature is 80 C. (Cv = 7.5 + 3.2 x 10 T, cal/ mol K). The change in the internal energy of the process is… a. 3210.5 cal b. 2105.3 cal c. 2015.3 cal d. 1203.5 cal

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31. A 0.8-m cylinder contains nitrogen gas at 600 kPa and 300 K. Now the gas is compressed 3 isothermally to a volume of 0.1 m . The work done on the gas during this compression process isa. 746 kJ b. 0 kJ c. 420 kJ d. 998 kJ 32. An ordinary egg with a mass of 0.1 kg and a specific heat of 3.32 kJ/kg-°C is dropped into boiling water at 95°C. If the initial temperature of the egg is 5°C, the maximum amount of heat transfer to the egg isa. 12 kJ b. 30 kJ c. 24 kJ d. 18 kJ 33. A piston–cylinder device contains an ideal gas. The gas undergoes two successive cooling processes by rejecting heat to the surroundings. First the gas is cooled at constant pressure until T2 = ¾T1. Then the piston is held stationary while the gas is further cooled to T3 = ½T1, where all temperatures are in K. The ratio of the final volume to the initial volume of the gas isa. 0.25 b. 0.50 c. 0.67 d. 0.75 34. From problem #33, The work done on the gas by the piston isa. RT1/4 b. Cv T1/2 c. Cp T1/2 d. (Cv+Cp)T1/4 35. From problem #33, The total heat transferred from the gas isa. RT1/4 b. CvT1/2 c. CpT1/2 d. (Cv+Cp)T1/4 36. MRII Question. An adiabatic tank contains 20 kg of water. A 220V, 0.1A motor drives a paddle wheel and runs for 45 minutes. Determine the change in the total energy of the system. a. 59.4 kJ b. 55.6 kJ c. 52.4 kJ d. 62.3 kJ 37. MRII Question. It is the heat effect accompanying a change in phase at constant temperature. a. sensible heat c. heat capacity b. latent heat d. heat of formation 38. Steam enters a diffuser steadily at 0.5 MPa, 300°C, and 122 m/s at a rate of 3.5 kg/s. The inlet area of the diffuser is2 2 2 2 a. 15 cm b. 50 cm c. 105 cm d. 150 cm 39. Water flows through a constriction in a horizontal pipe. As it enters the constriction, the water’s: a. speed increases and pressure decreases c. speed increases and pressure increases b. speed increases and pressure is constant d. speed decreases and pressure increases 40. A heat enginea. converts heat input to an equivalent amount of work b. converts work to an equivalent amount of heat c. takes heat in, does work, and loses energy heat d. uses positive work done on the system to transfer heat from a low temperature reservoir to a high temperature reservoir 41. A heat engine that in each cycle does positive work and loses energy as heat, with no heat energy input, would violatea. the zeroth law of thermodynamics c. the second law of thermodynamics b. the first law of thermodynamics d. the third law of thermodynamics 42. A Carnot cyclea. is bounded by two isotherms and two adiabats on a p-V graph b. consists of two isothermal and two constant volume processes c. is any four sided process on a p-V graph d. only exists for an ideal gas 43. The change in entropy is zero for: a. reversible adiabatic processes c. reversible processes during which no work is done b. reversible isothermal processes d. reversible isobaric processes 44. Which of the following processes leads to a change in entropy of zero for the system undergoing the process? a. Non-cyclic isobaric (constant pressure) c. Non-cyclic isothermal (constant temperature) b. Non-cyclic isochoric (constant volume) d. Any closed cycle 45. An ideal gas expands into a vacuum in a rigid vessel. As a result there is: a. a change in entropy c. a change in temperature b. an increase of pressure d. a decrease of internal energy

46. A copper block (Cp = 0.398 kJ/kg K) having a mass of 15 kg and a temperature of 500 K is placed in a well insulated vessel containing 100 kg of water initially at 300 K. The entropy change in this process (in kJ/kg) isa. 0.912 b. 3.906 c. 2.994 d. 6.521 47. MRII Question. According to ___________, it is impossible to create a device in which the only effect is to transfer heat from low temperature to high temperature. a. Kelvin Planck b. Clausius c. Carnot d. Clapeyron 48. Air at 20°C and 5 atm is throttled by a valve to 2 atm. If the valve is adiabatic and the change in kinetic energy is negligible, the exit temperature of air will bea. 10°C b. 14°C c. 17°C d. 20°C 49. The drinking water needs of an office are met by cooling tab water in a refrigerated water fountain from 23°C to 6°C at an average rate of 10 kg/h. If the COP of this refrigerator is 3.1, the required power input to this refrigerator isa. 197 W b. 612 W c. 64 W d. 109 W 50. Throttling process is a/an __________ process. a. reversible and isothermal c. reversible and constant enthalpy b. reversible and constant entropy d. irreversible and constant enthalpy 51. In case of an __________ process, the temperature of the system increases. a. adiabatic compression c. isothermal expansion b. isothermal compression d. adiabatic expansion 52. The third law of thermodynamics states that thea. heat capacity of a crystalline solid is zero at absolute zero temperature. b. heat transfer from low temperature to high temperature source is not possible without external work. c. gases having same reduced properties behave similarly. d. none of these. 53. The main feature of Carnot refrigeration cycle is that, ita. accomplishes the reverse effect of the heat engine. b. does not need the addition of external work for its functioning. c. transfers heat from high temperature to low temperature. d. none of these 54. Degree of freedom of the system ice-water-vapor will bea. 1 b. 3 c. 0 d. 2 55. Degree of freedom of the system liquid water with its vapor will bea. 1 b. 3 c. 0 d. 2 56. Degree of freedom of the system liquid solution of alcohol in water in equilibrium with its vapora. 1 b. 3 c. 0 d. 2 57. For any system, what is the minimum number of degrees of freedom? a. 0 b. 1 c. 2 d. 3 58. Given the table below for Freon 12 (entropy in BTU/ lb °R; enthalpy in BTU/lb; specific volume in 3 ft /lb)-

What is its state at 40°F and 25 psia? a. saturated liquid c. compressed liquid b. superheated vapor d. saturated vapor 59. Using the previous Freon 12 data table in problem #58, what is its entropy in BTU/lb °R at 120°F and 80% quality? a. 0.057 b. 0.144 c. 0.186 d. 28.8 60. Using the previous Freon 12 data table, what is its latent heat (heat of vaporization) in BTU/1b at 80°F? a. 0.219 b. 0.423 c. 26.4 d. 58.9

61. Work or energy can be a function of all of the following except: a. force and distance c. power and time b. torque and angular rotation d. force and time 62. (U + PV) is a quantity calleda. flow energy b. shaft work c. entropy d. enthalpy 63. ChE Board Exam Nov. 2009. A chemical engineer wants to extract energy from a geothermal power plant. At the top of the reservoir, the temperature of water is 30° C and as the water goes out of the coils, the temperature is 20°C. If we analyze 2000 kg of water, how much maximum power can we extract from the reservoir? Let specific heat capacity of water be 4.186 kJ/kg °C. a. 83,720 kJ b. 2,763 kJ c. 2,536,720 kJ d. 80,957 kJ 64. Consider a Carnot refrigerator and a Carnot heat pump operating between the same two thermal energy reservoirs. If the COP of the refrigerator is 3.4, the COP of the heat pump isa. 1.7 b. 2.4 c. 3.4 d. 4.4 65. Steam is condensed at a constant temperature of 30°C as it flows through the condenser of a power plant by rejecting heat at a rate of 55 MW. The rate of entropy change of steam as it flows through the condenser isa. –1.83 MW/K b. –0.18 MW/K c. 0 MW/K d. 0.56 MW/K 66. Steam is compressed from 5 MPa and 300°C to 10 MPa isentropically. The final temperature of the steam isa. 290°C b. 300°C c. 311°C d. 401°C o o 67. Given that molar Cp of CO2 is 8.92 BTU/lbmol R, and molar Cp of N2 is 6.95 BTU/lbmol R, the calculated Cp per pound of mixture containing 25 vol% CO2 and 75 vol% N2 is: o o a. 0.23 BTU/lb °R b. 2.23 BTU/lb R c. 5.21 BTU/lb °R d. 7.44 BTU/lb R 68. For an ideal liquid solution, which of the following is unity? a. Fugacity coefficient b. Activity c. Fugacity d. Activity coefficient 69. In an ideal gas mixture, fugacity of a species is equal to itsa. partial pressure b. vapor pressure c. chemical potential d. none of these 70. An apple with an average mass of 0.15 kg and average specific heat of 3.65 kJ/kg-°C is cooled from 20°C to 5°C. The entropy change of the apple isa. –0.0288 kJ/K b. –0.192 kJ/K c. -0.526 kJ/K d. 0 kJ/K 71. MRII Question. The cooling energy ratio of a refrigeration cycle operating at -12°C and 31°C isa. 4.39 b. 3.58 c. 6.07 d. 5.19 72. An inventor suggests that a house might be heated by using a refrigerator to draw energy as heat from the ground and reject energy as heat into the house. He claims that the energy supplied to the house as heat can exceed the work required to run the refrigerator. This: a. is impossible by first law b. is impossible by second law c. is impossible since heat energy flows from the (hot) house to the (cold) ground d. is possible 73. In a thermally insulated kitchen, an ordinary refrigerator is turned on and its door is left open. The temperature of the room: a. remains constant according to the first law of thermodynamics b. increases according to the first law of thermodynamics c. decreases according to the first law of thermodynamics d. remains constant according to the second law of thermodynamics 74. An experimental electric jeepney running in Makati on 12V battery at 20m/s has a total energy 7 storage of 2.0x10 Joules. If 8.0 KW is needed to move the vehicle, what is the quantity of energy supplied to the motor and how far will it travel a. 500 A, 35km b. 814 A, 60km c. 960 A, 71km d. 667 A, 50km 3 3 75. An airjet operates at 2,500 rev/min and uses 7.89 x 10 J of energy and exhausts 4.58 x 10 J for each crankshaft revolution. Determine the quantity of gasoline fuel consumed in one hour of 7 operation if the heat of combustion is 4.03 x 10 J/liter. a. 24.2 L/hr b. 29.4 L/hr c. 13.4 L/hr d. 2.05 L/hr