课程名称︰物理化学上 课程性质︰农业化学系大二必修 课程教师︰苏志明 开课学院：生物资源暨农学院 开课系所︰农业化学系 (化学系开课) 考试日期（年月日）︰2009年 1月15日 考试时限（分钟）：125 min 是否需发放奖励金：YES!! （如未明确表示，则不予发放） 试题 : 1.(a) Assuming that glucose and water form an ideal solution, what is the equilibrium vapor presure at 20℃ of a solution of 1.00 g of glucose (mol wt. 180) in 100 g of water? The vapor pressure of pure water is 17.54 torr at 20℃. (b) What is the osmotic pressure, in torr, of the solution in part (a) versus pure water? (c) What is the activity of water as a solvent in such a solution? (d) What would be the osmotic pressure versus pure water of a solution containing both 1.00 g of glucose and 1.00 g of sucrose (mol wt. 342) in 100 g of water at 20℃. 2. Which of the following has the largest (most positive) value for the: (a) Molar entropy increase? (Ⅰ) H2O(l,0℃) ─→ H2O(l,100℃) (Ⅱ) H2O(s,0℃) ─→ H2O(l,0℃) (Ⅲ) H2O(l,100℃) ─→ H2O(g,1atm,100℃) (Ⅳ) H2O(g,1atm,100℃) ─→ H2O(g,0.1atm,100℃) (b) Free energy of transfer of 1 mol of the substance from inside to out- side a cell, all at 37℃? (Ⅰ) NaCl(a＝0.010 inside) ─→ NaCl(a＝0.140 outside) (Ⅱ) KCl (a＝0.100 inside) ─→ KCl (a＝0.005 outside) (Ⅲ) NaCl(a＝0.100 inside) ─→ NaCl(a＝0.200 outside) 3. Consider the nitrogen gas at 25℃ and 1 atm. In hard-sphere model, the diameter of an N2 molecule can be taken as 3.74 A (3.74x10^-10 m). (a) Calculate the mean speed and the mean square speed of the nitrogen molecule. (b) Calculate the number of collisions each nitrogen molecule encounter in 1 sec. (c) Calculate the total number of collisions in a volume of 1 m^3 in 1 s. (d) Calculate the mean free path of a nitrogen molecule. (e) What is the total distance traveled by one N2 molecule along the zigzag path in 1 s? (f) As described in (e), estimate how far it will move in 1 s away from where it started. 4. The problem of the separation and purification of protein molecules through density-gradient centrifugation is equivalent to the problem of the flight heights of hydrogen(or helium)-filled balloons in the atmosphere. Assuming that our atmosphere is consisted of pure nitrogen gas and the temperature is uniformly at 25℃, the pressure is exactly at 1 atm on the earth surface, and the gravitational acceleration g is 9.80 m/s^2 and may be taken as a constant, answer the following questions: (a) Taking the gravitational potential be 0 at the earth surface, what is the gravitational potential at an elevation of h? What are the density and pressure of nitrogen gas at the elevation of h? (b) What are the atmospheric pressure (in atm) and the nitrogen gas density (in the unit of g/L) at the top of Jade Mountain which has an altitude of 4000 m? (c) What would be the buoyancy forces for a 1 L balloon at the earth surface and also at the top of the Jade Mountain, respectively? Here we assume that the balloon size is constant. (d) If the 1 L balloon has a mass of 0.3 g, and assuming the balloon size is constant, theoretically, how high could the balloon reach? Note that this situation is equivalent to the equilibrium position of a protein molecule in a centrifuge tube under the density-gradient centrifugation condition. 5. The diffusion coefficient D of ribonuclease from bovine pancreas, an enzyme that digests RNA, has been measured in a dilute buffer at 20℃. The value is D＝13.1x10^-7 cm^2/s. (Hint: be careful with the units) (a) Calculate the frictional coefficient f. (b) Assuming that the protein molecule is sphere, calculate its hydrodynamic radius from the Stokes equation. The viscosity of dilute aqueous buffer is approximately equal to 1.00x10^-2 g/s*cm. ------------------------------------------------------------------------------ Some constants and equations: 1 L*atm＝24.2 cal; 1 cal＝4.18 J; Ｒ＝0.082 L*atm/℃*mol＝8.31 J/K*mol; k＝1.38x10^-23 J/K＝1.38x10^-16 erg/K; 1 erg＝1 g*cm^2/s^2; 　　　　o　 μ＝μ ＋ＲＴ㏑ａ; ΠＶ＝ｎＲＴ; <ｕ>＝(8kT/πm)^0.5; <ｕ^2>＝(3kT/m); z＝(√2)π(Ｎ/Ｖ)σ^2<ｕ>; l＝<ｕ>/z; d^2＝zl^2 (random walk model); D＝kT/f; f＝6πηr --

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