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(CENG131)[2009](s)midterm~1021^_10027.pdf
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CENG 131
CHEMICAL ENGINEERING THERMODYNAMICS
HONG KONG UNIVERSITY OF SCIENCE AND TECHNOLOGY, SPRING 2009
MIDTERM EXAM
NAME: STUDENT ID#:
INSTRUCTIONS
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This is an open-book, open notes exam.

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Read the questions carefully before you start. Do not spend too much time on any one question.

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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 (20%)
Answer (T/F)
1. No heat is exchanged in an isothermal process.
2. You can fix the intensive state of a simple system containing a pure substance in equilibrium if you know the molar entropy, S, and the molar exergy, X.
3. At a given temperature and pressure, the constant-pressure heat capacity, CP, has the same value for any ideal gas.
4. The molar entropy does not change for a closed system undergoing a reversible process.
5. Any system is at equilibrium if its total entropy, S, is at a maximum.
6. The acentric factor, , measures the deviation of a real gas from an ideal gas.
7. The molar entropy of an incompressible fluid is a function of temperature only.
8. For pure water at the critical point, the solid, liquid and vapor phases coexist at equilibrium.
9. A closed system undergoing a reversible, isobaric expansion does not produce any work.

10. If F is a state function of two variables X, Y, then the following is always true: . . . . . . . . . . .

MULTIPLE CHOICE QUESTIONS (30%)
Answer
(A/B/C/D)
11. The Joule-Thomson coefficient is defined as . . . Which of the following expression is correct? A. . . . . . . . . B. . . . . . . . . C. . . . . . . . . D. . . . . . . . .
12. A stream of ideal gas at (298 K, 10 bar) is expanded to 1bar. Assuming the surroundings acts as a heat reservoir at 298 K, which of the following devices will produce the most work from the gas expansion at steady state? A. A throttling valve B. An adiabatic and reversible turbine C. An adiabatic and irreversible turbine D. An isothermal and reversible turbine
13. For the same molar flow rate in the same pipe, a stream of ideal gas (1) at (. . . . . . can produce more work than another stream of ideal gas (2) at (. . . . . . because: A. Stream 1 has more internal energy B. Stream 1 has more enthalpy C. Stream 1 has less entropy A. Stream 1 has more kinetic energy
14. When you increase the pressure of water, how will the melting point, , and boiling point, , change? Hint: Consider the Clapeyron Equation. Also, unlike most substances, water expands as it freezes. A. . increases, . increases B. . decreases, . decreases C. . increases, . decreases D. . decreases, . increases

15. We can fix the intensive state of a simple system of an incompressible liquid at equilibrium if we know: B. The molar volume, V, and the temperature, T C. The molar enthalpy, H, and the temperature, T D. The molar entrop