課程名稱︰物理化學上 課程性質︰農化系必修 課程教師︰李弘文 開課學院： 開課系所︰農化系 考試日期（年月日）︰2012.10.18 考試時限（分鐘）：110分鐘 是否需發放獎勵金：是 （如未明確表示，則不予發放） 試題 : (註：本試題提供考試會用到的所有公式) Part A: True/False Questions(50 points, 2 for each question.) For the statement to be true , it must be always true. 2points for each correct answer, and 1 point will be subtracted from each incorrect answer. (a) Typical mean free path of a gas at 300K and 1 atm is about 1 mm. (b) If collisions among gas molecules are inelastic, the pressure of the container wall will be higher than the expected value from the elastic condition. (c) The same number of O2 gas molicules are put into two containers of different sizes at the same temperature. The gas in smaller container has hogher Vrms speed. (d) In 3-dimentional Maxwell speed distribution, most probable speed is larger than the root-mean-squared speed. (e) If a system expands irreversibly at constant temperature, w = -q . irrev (f) No work can be done from an isothermal cyclic process. (g) Area under heat capacity-temperature curve equals heat. (h) Mixing ideal gases laways leads to an increase in entropy. (i) Joule's free expansion experiment is a constant internal energy process. (j) For ideal gas, μ is zero. J-T (k) The internal energy, U, is independent of P for an ideal gas. x (l) (ye +xy+xlny) is a not state function. (m) To liquefy a gas, it is necessary to prepare gas within the temperature and pressure range that Joule-Thomson coefficient is negative. (n) In an adiabatid process, there is no heat exchange; therefore the temperature is constant. (o) To heat up gas at constant pressure, system must do work to the surrounding. (p) If the standard reaction enthalpy for a chemical reaction dies not change appreciably with temperature, the heat capabilities of both reactants and products must be small. (q) A reversible gas expansion process achieves maximum amount of work. (r) The entropy of any system remains constant when a reversible process occurs. (s) The Carnot engine sets the upper limit of efficiency of heat engines. (t) △S =△H/T for any reversible process at constant temperature. dq (u) Clauius inequality states that ∫--- < 0. T = (v) △S for the vaporization process of a pure substance is alwaus positive. (w) The Carnot analysis suggests that running an engine at colder temperature is more dfficient. ∂V (x) For liquid and solid, (-----) is very small, so Cp is about the same ∂T P as Cv. (y) It is impossible for any system to operate in a cycle that takes heat from a hot reservoir and converts it to work in the surroundings without transferring some heat into a colder reservoir. PartB: Short calculation questions(31 points) 1. (3pts)At what temperature is the Vrms of Ar equal to that of SF6 at 300K?(MW of Ar=40.0gmol^-1 and MW of SF6=146gmol^-1) 2. (10pts)A 1.50 mole sample of an ideal gas, for which Cv,m =3/2 R, is subjected to two successive changes in state: (1) From 25.0℃ and 105.0x10^3 Pa, the gas is expanded isothermally against a constant pressure of 12.5x10^3 Pa to twice the initial volume. (2) At the end of the previous process, the gas is cooled at constant volume from 25.0℃ to -30.0℃. Calcuate q, w, △U, △H, and △Ssys of the whole process. 3. (3pts) Given the following heat capacity data (at 298.15K), calculate o △H of CO2 = -393.5kJ mol^-1 at 298.15K) f Substance C(graphite) O2(g) CO2(g) -1 -1 Cp,m/Jmol K 8.52 28.8 37.1 4. (10pts)Calculate w, q, △U, △H, and △Ssys for the process in which 2.50 mol of water undergoes the transition H2O(l,373K)→H2O(g,610K) at -5 3 -1 1 bar of pressure. The volume of liquid water at 373K is 1.89x10 m mol -2 3 -1 and the molar volume of steam at 373 and 610K is 3.03x10 m mol and -2 3 -1 5.06x10 m mol , respectively. For steam Cp,m can be considered constant -1 -1 over the temperature interval of interest at 33.58Jmol K (△Hvaporization =40656J/mol) 5.(5pts) Calculate △S, △S , and △S when the volume of univ surroundings 168.0g of CO initially at 273.0K and 1 bar increases by a factor of two in volume by an isothermal expansion step against P = 0 . external -1 -1 Take Cp,m to be constant at the value 29.14J mol K and assume ideal gas behavior. State whether process is spontaneous. The temperature of the surrounding is 273.0 K . (MW of CO = 28.01gmol^-1) PartC: Description questions (19points) (5points) (1A) Explain how DSC experiment works, and plot a typical DSC curve (Cp vs. T) for a protein undergoing reversible thermal denaturation. (5points) (1B) Explain why Joule-Thomson experiment is a constant enthalpy process. (2) (9pts, 3 pts for each process; must answer all correctly in each process to get the points)For each of the following process, fill in the table for each of the quantities (q, w, △U, △H, △Ssys) (A) A sample of water is boiled at 100℃ and 1.0 atm. (B) An ideal gas is carried through a reversible, cyclic Otto cycle in steps of adiabatic compression, heating at a constant volume, adiabatic expansion, and cooling at constant volume. (C) An ideal gas is carried through a reversible, cyclic Carnot in a reversed direction. q w △U △H △Ssys A B C (Fill the blank with sign +,- or 0) -End of Exam- --

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