课程名称︰物理化学上 课程性质︰农化系必修 课程教师︰李弘文 开课学院： 开课系所︰农化系 考试日期（年月日）︰2012.12.03 考试时限（分钟）：110分钟 是否需发放奖励金：是 （如未明确表示，则不予发放） 试题 : Part A: True/False questions(40 points, 2 point for each question) For the statement to be true, it must be always true. If the statement is false, simply circle the wrong statement or cerrect the statement to make it true. 2 points for each correct answer, and 1 point will be subtracted from each incorrect answer. o (a) For a spontaneous process at constant T and P, △G is always negative. o (b)△G is a temperature-independent constant. (c) When urea spontaneously dissolves in water, the geaker of solution feels cold. This is an entropy-driven process. (d) Equilibrium constants (Kp) for reactions involving only gases depend on trmperature, but not on pressure. (e) △G is the maximum non-expansion work that a system can do at constant T and V. (f) In the case of 0.01 moles of Ar and 1 mole of N2 mixing together. at constant T and P, the sign of △Smix, △Hmix, and △Gmix is (+,0,-). (g) The negative change in Helmholtz free energy during an isothermal process is the maximum work available from the processes. (h) For real gas with compressibility factor Z>1, molecular interaction is dominated by attraction potential. (i) Both van der Waals parameters a and b are larger for Ar gas than those for Ne gas. (j) Nitrogen and methane gases in the corresponding states have the same value of Z. (k) Critical temperature (Tc) and creitical pressure (Pc) can be expressed by van der Waals parameters a and b. (l) For a one-component system, when the pressure is feduced, the amount of the boiling temperature change is always smaller than that of the freezing temperature. (m) The Clausius-Clapeyron equation can be applied to a solid-liquid phase transition. (n) At equilibrium, a substance that occurs in two phases has the some concentration in both phases. (o)At constant temperature, for one-component system, μ(P2)<μ(P1) when P2<P1. (p) In the P-V phase diagram for a one-component system, the liquid/gas coexistence is descrebed by a line. (q) For an ideal solution of two substances A and B, μ must be smaller than A o μ . A (r) When azobenzene of molar fraction of 0.05 is addid to a pure benzene solution, the change of chemical potential of benzene is RTln(0.05). (s) If solutions of a same single solute are prepared at equal molalities but in different solvents, the boiling temperature change of the solvent will be the same for these ideal solutions. (t) Based on the phase rule, a two-component system with a liquid/gas coexistence has no degree of freedom. Part B: Calculation and Descreption questions: (28pts)(1) At 298K, the vapor pressure of pure benzene is 96.4 torr, and that of the solvent will be the same for these ideal soltions sontains 3.0 mole of benzene and 2.0 mole of toluene. Assuming the ideal behavior, andwer the following questions. (4pts)(1A) Plot the P-Z phase diagram at 298K, and specify (a) the benzene bubble line (──) and dew line(----); (b) the phase at diffefent regions. ↑ ↑ │ │ P │ │ │ │ │ │ │ │ └───────┘ Z benzene (3pts)(1B) At 298K, when the pressure is reduced from 760 torr, at what pressure would the vapor phase appear first? (12pts)(1C)When the 1.5 mol of the solution has been converted to vapor, calculate the molar fractions of benzene at liquid and vapor phase. (5pts)(1D) Now toughly sketch the T-Z phase diagram at constant benzene pressure. Specify (a) the bubble line (──)and dew line(----) ; (b) the phase at different regions; (c) the relative magnitude and physical meaning of temperatures at Z =0 and 1. benzene ↑ ↑ │ │ T │ │ │ │ │ │ │ │ │ │ └──────┘ (5pts)(1E) explain how "fractional distillation" works using typical fractional distillation words using typical fractional distillation column in organic laboratory. In the case of benzene and toluene mixture, which compound can be purified at the top of the column? (8pts)(2) First, disign a set of experiments to determine all the o o o thermodynamics parameters(K, △G , △H , △S ) of a biochemical reaction. Then, explain how to use the experimental results to determine all 4 o o o parameters. Assume that △G , △H and △S are constant over the experiments. (8pts)(3) Sketch a P-T phase diagram of pure water. Specify (a) the phase in each region, (b) triple point and (c) critical point. Also explain the sign and magnitude of slopes along co-existence lines. (8pts)(4) Calculate Kp at 298K and 500K for the reaction 1 NO + ── O →NO assuming that △H is costant (g) 2 2 (g) 2(g) rxn over the interval 298-600K. Do you expect Kp to increase of decrease at temperature is increased to 600K? o 3 -1 o 3 -1 △H (NO ,g)=33.2x10 Jmol , △H (NO,g)=91.3x10 Jmol f 2 f o 3 -1 o 3 -1 △G (NO ,g)=51.3x10 Jmol , △G (NO,g)=87.6x10 Jmol f 2 f (10pts)(5) A 2.75 mole of Ar undergoes an isothermal reversible expansion from an initial volume of 5.0L to a final volume of 95.0L at 320K. Calculate the work done in the process using (5A) the ideal gas and (5B) van der Waals equations of state (dw=-PdV) 6 -2 -5 3 -1 (van der Waals paremeters of Argon:a=0.1355m Pa mol , b=3.2x10 m mol ) (6pts)(6) Benzene(l) has a vapor tressure of 0.1369 bar at 298K and an enthalpy of vaporization of 32.72kJmol^-1, restectively. Calculate the vapor pressure of benzene(l) at 340K assuming that the enthalpy of vaporization does not change with temperature. (12pts)(7)A protein P (membrane receptor) involved on signaling pathway has been found to follow the following obligatory sequential binding scheme to proceed with the signaling cascade: Po + L ←→ PL + M ←→ PLM K1 K2 Protein Po has to bind to ligand L first in order to bind to ligand M. The dissociation constants of these two binding processes are K1 and K2. (6pts)(7A)Express Y , the fraction of protein that is bound only by ligand PL L (PL), in the Langmuir form in terms of K1, K2, L, and M. (6pts)(7B) Plot Y vs. [L] . Also, identify the value and position of the observed dissociation constant Kobs, the maximum Ymax value in the plot. ↑ │ │ Ymax│_ _ _ _ _ _______ │ │ ／ Y │ │ ／ PL │ │╱ │ ∕ │∕│ └──────────→[L] Kobs --

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