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(CENG2210)[2012](s)midterm~=n19gpimcb^_52550.pdf
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CENG 2210
CHEMICAL ENGINEERING THERMODYNAMICS
HONG KONG UNIVERSITY OF SCIENCE AND TECHNOLOGY, SPRING 2012
MIDTERM EXAM
NAME: STUDENT ID#:
INSTRUCTIONS
. Read the questions carefully before you start. Do not spend too much time on any one question.
. You will not be graded on presentation and problem formulation in this exam. However, points will still be deducted if we cannot read or understand your solution.
TRUE/FALSE QUESTIONS (15%)
Answer (T/F)
1. During a sudden expansion against vacuum, the pressure of the expanding gas becomes zero once the expansion starts.
2. For an irreversible process taking a simple system from state A to state B, it is impossible to construct a reversible process to restore the system from state B to state A.
3. A Carnot engine can be run in reverse, removing heat from the cold reservoir and dumping a fraction of it into the hot reservoir.
4. The constant-volume heat capacity, .., is a function of temperature only for an ideal gas.
5. To fix the intensive equilibrium state of a simple system in vapor-liquid equilibrium, one only needs to specify one intensive property.
MULTIPLE CHOICE QUESTIONS (20%)
Answer (A/B/C/D)
6. Assuming you can evaluate the residual molar enthalpy at any conditions, which of the following expression should you use to calculate the molar enthalpy change of a real gas from state 1 .......to state 2 .......? A. .. ... ...................... .. .... .. .. B. .. ... ...................... .. .... .. .. C. .. ... ...................... .. .... .. .. .. ....... .. . . ... .. .. D. .. ... ...................... .. .... .. .. .. ....... .. . . ... .. ..
7. If you are trying to determine the molar volume of steam at .......... .... .., which of the following will give you the most accurate answer? A. The ideal gas law B. The Redlich-Kwong equation of state C. The Lee-Kesler correlation D. The van der Waals equation of state
8. The partial derivative ........ for an ideal gas is equal to: A. ........ B. ........ C. ....... D. .
9. In calculating the heat of an isobaric process involving a gas in a piston-cylinder assembly, which of the following assumption is not necessary to use the equation ....... ....? A. The gas is an ideal gas. B. The constant-pressure heat capacity is constant. C. The process is quasi-static. D. The kinetic and potential energy of the gas can be ignored.
10. A pure substance is in vapor-liquid equilibrium. If we fix the temperature, which of the following quantity may still have more than one possible value? A. The pressure B. The total volume (vapor plus liquid) C. The molar entropy of the vapor phase D. The latent heat of vaporization
QUESTIONS (65%)
11. (18%) A Carnot cycle operates between a hot heat reservoir at ......!and a cold heat reservoir at ......!, using carbon dioxide as the working fluid.
Saturated carbon dioxide liquid at State 1.......enters the evaporator, where it absorbs heat from the