课程名称︰物理化学一 课程性质︰必修 课程教师︰戴子安 开课学院：工学院 开课系所︰化工系 考试日期（年月日）︰101.01.09 考试时限（分钟）：150分钟 是否需发放奖励金：是 （如未明确表示，则不予发放） 试题 : 1.(40 points) Explain the following terms or physical phenomena. Use graphs if necessry. (a) Plot the Gibbs energy vs. the extent of reaction, ξ, for a reaction that goes nearly to completion and indicate its corresponding reaction Gibbs energy on the plot. (b) For a simple gas reaction A → B, plot the Gibbs energy vs. the extent of reaction for the corresponding hypothetical without any mixing and without any reaction. (c) Consider an endothermic reaction A → B and the density levels in B are much greater than those in A. Explain at the equilibrium why B molecules can be dominant based on the Boltzmann's theorem. (d) Explain how pressure affects equilibrium composition for a reaction. (e) Explain how pressure affects the melting and boiling points for a pure spcies. (f) Based in the Ehrenfest classification, plot μ, V, H, S, Cp as a function of temperature for the first order transtion. (g) Explain how the activity of a liquid in a mixture can be determined. (h) Plot phase diagram in the terms of T. vs. composition for a binary solution that shows a positive deviation from the Raoult's law. (i) For a nicotine/water mixture, explain why the system shows both LCST and UCST. (j) Calculate the pressure differential of water across the surface of a spherical droplet of radius 100nm at 25°C(The surface tension for water is γ=71.97 mN/m .) 2.(10 points) At 2000°C, water is 2％ dissociated into oxygen and hydrogen at a total pressure of 1bar. (a) Calculate the equilibrium canstant Κ for H2O(g) = H2(g) + 1/2 O2(g) (b) Will the extent of reaction increase or decrease if the pressure is reduced (c) Will the extent of reaction increase or decrease if argon gas is added, holding the total pressure equal to 1bar? (d) Will the extent of reaction change if the pressure is raised by addition of argon gas at constant volume to the closed system containing partially dissociated water vapor? 3.(15 points) The shells of marine organisms contain calcium carbonate CaCO3, largely in a crystalline form known as calcite. There is a second crystalline form of a calcium carbonate known as aragonite. Physical and thermodynamic properties of calcite and aragonite are given below. ─────────────────────────────────────── Properties(Τ＝298Κ,Ρ=1bar) calcite aragonite ─────────────────────────────────────── Δf Η° (kJ/mol) 1206.9 1207.0 ─────────────────────────────────────── Δf Ｇ° (kJ/mol) -1128.8 -1127.7 ─────────────────────────────────────── Ｓ° (J/Kmol) 92.9 88.7 ─────────────────────────────────────── Cp° (J/Kmol) 81.9 81.3 ─────────────────────────────────────── Density (g/mL) 2.71 2.93 ─────────────────────────────────────── (a) Based on the data given, would you expect an isolated sample if calcite at Ｔ=298Ｋ and Ρ=1bar to convert to aragonite, given sufficient time?Explain (b) what pressure must be achieved to induced the conversion of calcite to aragonite at Ｔ=298Ｋ. Assume both calcite and aragonite are incompressible at Ｔ=298Ｋ . 4.(10 points) Calculate the Δr Η° and Δr Ｓ°for the reaction N2(g) ＋ O2(g)＝2NO(g) from the folling values of equilibrium constant Κ. ┌────┬───┬───┬───┬───┬───┬───┬───┬───┐ │Τ∕Κ │ 1900 │ 2000 │ 2100 │ 2200 │ 2300 │ 2400 │ 2500 │ 2600 │ ├────┼───┼───┼───┼───┼───┼───┼───┼───┤ │Κ/10^-4│ 2.31 │ 4.08 │ 6.86 │ 11.0 │ 16.9 │ 25.1 │ 36 │ 50.3 │ └────┴───┴───┴───┴───┴───┴───┴───┴───┘ 5.(10 points) Show that if the vapor pressure of a solute follows Henry's law, then in dilute solution its chemical potential follows an equation very much like that for an ideal solution. 6.(10 points) A solution of polystyrene in benzene contains 10g/L. The equilibrium height of the column of a solution (density =0.88g/cm3 ) in the osmometer corrected for capillary rise is 11.6cm at 25°C. What is the molecular weight of the polystryene. 7.(15 points) The temperature-composition diagram for Ca/Si binary system is shown below. (a) Identify eutectics, congruent melting compounds, and incongruent melting compounds, (b) If a 20 percent by atom composition melt of silicon at 1500°C is cooled to 1000°C, what phases(and phase composition) would be at equilibrium? Estimate the relative amounts of each phase. (c) Describe the equilibrium phases observed when an 80 percent by atom composition Si melt is cooled to 1030°C. What phases, and relative amounts would be at equilibrium at a temperature (i) slightly higher than 1030°C (ii) slightly lower than 1030°C (d) Sketch the cooling curve if the 80 percent of Si melt is cooled to the room temperature. 第七题附图 http://ppt.cc/Mm-B --

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