课程名称︰化工热力学甲一 课程性质︰化工系必修 课程教师：林祥泰 开课学院：工学院 开课系所︰化工系 考试日期（年月日）︰2013/11/26 考试时限（分钟）：120min 是否需发放奖励金：是 （如未明确表示，则不予发放） 试题 : 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. 图片网址 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] --

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