課程名稱︰化工熱力學甲一
課程性質︰化工系必修
課程教師：林祥泰
開課學院：工學院
開課系所︰化工系
考試日期（年月日）︰2013/11/26
考試時限（分鐘）：120min
是否需發放獎勵金：是
（如未明確表示，則不予發放）
試題 :
Second Midterm Exam
Closed book and notes
Note: Credit for each problem is given in the square brackets []. Totally 100
pts.
l.
(a) Show that for a closed system kept under constant temperature (T) and
pressure (P). its Gibbs free energy reaches minimum at equilibrium. [5 pts]
(b) Show that at equilibrium the temperature, pressure, and chemical potential
does not vary with location in the previous system. [5 pts]
2.
The pressure (P)-volume(V) isotherm of water at 400 K calculated from the PR
EOS is show in the figure on the right. The dashed line is the vapor presure
(2.41 bar) of water at 400K.
圖片網址 http://ppt.cc/OYvB
(a) Indicate the vapor and liquid phases that at may coexist in equilibrium
at 400 K. (provide your answer in terms of pointsA, B, C, etc.) What are
the molar volumes, respectively? [4 pts]
(b) Is it possible to have a water vapor at 400 K and 100 bar? If not, explain
why and state the maximum pressure of water vapor that one can have at
400 K.[4 pts]
(c) Suppose a water vapor is compressed isothermally at 400 K from 0.1 m^3/mol
to 2.3x10^-5 m^3/mol. How would the state of water change if the
compression is done slowly and carefully? (provide your answer in terms of
points A, B, C, etc)[4 pts]
(d) Following (c) what if the compression is done rapidly? [4 pts]
(e) Determine the fugacity of water at points A to G, respectively. [7 pts]
(f) Suppose the enthalpy and entropy of ideal gas water at 400 K and 1 bar is
zero (reference state), determine the Gibbs free energy of the saturated
vapor and liquid, respectively. [4 pts]
(g) Fllowing (f), determine the Gibbs free energy of point A. [3 pts]
3.
A steam turbine in a small electric power plant is designed to accept steam at
60 bar and 500°C and exhaust the steam at pressure 10 bar. The molar flow rate
of steam is 70 mol/s. Assuming that the turbine is adiabatic and has been well
designed (so that Sgen=0), we would like to compute the exit temperature of the
steam and the power generated by the turbine.
(a) Choose the turbine as the system and write down the balance equations for
this process. [6 pts]
(b) Express the thermodynamic properties from (a) in terms of departure
functions. [4 pts]
(c) Write down the procedure for solving this problem based on the PR EOS.
[5 pts]
4.
The vapor pressure of solid and liquid hydrogen cyanide (HCN) is given by
Solid: lnP = 26.397 － (4293.9/T)
Liquid: In P = 22.725 － (3345.8/T)
where the unit for P is Pa and for T is K. From these data, calculate
(a) the heat of sublimation [5 pts]
(b) the heat of vaporization [5 pts]
(c) the heat of fusion [5 pts]
(d) the triple point(temperature and pressure)[5 pts]
(e) The normal melting temperature of HCN is found to be 259 K, detennine the
entropy change upon melting at 259K?[5 pts]
(f) Following (e), determine the volume change upon melting (assuming that the
densities of liquid and solid HCN are temperature independent). [5 pts]
5.
Proteins can exist in one of two states, the active, folded state and the
inactive, unfolded state. Protein unfolding can be thought of as a first-order
phase transition from folded to unfolded (denaturation) with increasing
temperature. Denaturation is accompanied by an increase in molecular volume and
a signiant positive latent heat.
(a) Which state (denatured or folded) has the higher entropy? [5 pts]
(b) Sketch the Gibbs energy function for both D (denatured) and F (folded)
proteins, and identify T*, the phase transition temperattue. [5 pts]
(c) Does the transition temperature T* increase or decrease with the increase
of pressure? why? [5 pts]