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(ceng131)[2009](s)final~1021^_10026.pdf
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DEPARTMENT OF CHEMICAL & BIOMOLECULAR ENGINEERING
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Hong Kong University of Science and Technology
Final Examination C Spring Semester 2009/10



CENG 131 - Chemical Engineering Thermodynamics
Thursday, 20st May, 2010

Instructions to Students
1. Write your NAME and STUDENT ID on EACH answer sheet. Clearly mark which question you are answering if you use additional sheets of paper.



2. This is an open-book, open-notes examination.



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



4. 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.



5. No discussion or talking is allowed during the examination.








TRUE/FALSE QUESTIONS (16%)


Question
Ans
Explanation

1.


An ideal gas mixture must be an ideal solution.
T
An ideal solution requires that molecular sizes and interactions are similar among all components. An ideal gas mixture further requires that the molecular sizes and interactions are all zero. So an ideal gas mixture is always an ideal solution.

2.


For an ideal gas mixture, all residual properties are zero.
T
By definition, residual properties measure the deviation from ideal gas mixtures.

3.


For any given chemical reaction, the standard enthalpy of reaction is only a function of temperature.
T
The pressure (1 bar) and composition (pure in most cases, 1 molal in unit molality standard states) are fixed for the standard states. So we essentially define all standard state properties to be dependent only on temperature.

4.


A reversible process involving a closed system must also be isentropic if there is no heat exchanged.
T
Since ....=........../.. , if ..........=0, then .... must also be zero. For a closed system, N is also constant, so it implies the process is at constant molar entropy, i.e. isentropic.

5.


In an isolated system, a reaction will only proceed if it decreases the total Gibbs free energy, G of the system.
F
For this statement to hold, the system needs to be held at constant T, P. (For an isolated system, the equilibrium condition should be the maximization of entropy.)

6.


For any pure gas, its fugacity is equal to the pressure.
F
It is only for pure ideal gases that the fugacity will be equal to the pressure. For real gases, the fugacity is .....

7.


The equilibrium constant increases with increasing temperature for an exothermic reaction.
F
According to Le Chateliers principle, the reaction will proceed in such a way to oppose it. For a reaction that gives out heat (exothermic), an increase in temperature should cause the reverse reaction t