课程名称︰分析化学一 课程性质︰必修 课程教师︰刘春樱 开课学院：理学院 开课系所︰化学系 考试日期（年月日）︰2008/12/01 考试时限（分钟）：10:20 ~ 13:00 是否需发放奖励金：是 （如未明确表示，则不予发放） 试题 : Analytical Chemistry 1. (18%) Explain the following terms: a) chelate effect d) pseudohalide group b) buffer capacity e) desferrioxamine B c) thermal gravimetric analysis f) isoionic point 2. (15%) Make choice (please give the reason and theshape of the titration curve) to indicate volume relationships in the titration of following mixtures with HCl using phenolphthalein and bromocresol green indicator, respectively. (i) NaOH (ii) Na2CO3 (iii) NaHCO3 (iv) NaOH and Na2CO3 (v) Na2CO3 and NaHCO3. a) V phth < 1/2 V bcg d) V phth = 1/2 V bcg b) V phth > 1/2 V bcg e) V phth = V bcg c) V phth = 0 ; V bcg > 0 (V表到其指示剂终点所需HCl体积) 3. (4%) Define precipitation from homogeneous solution, and give an example. 4. (4%) Briefly describe and give an example of (a) a differentiating solute, and (b) a leveling solvent. 5. (12%) Calculate the percentage of unreacted NH4+ at the equivalence point in the titration of 0.20M NH4+ with (1) 0.20M NaOH in an aqueous solution (2) 0.20M C2H5ONa in anhydrous ethanol (Ks(H2O) = 1*10^-14, Ka(NH4+) in H2O = 6*10^-10 Ks(EtOH) = 8*10^-20, Ka(NH4+) in EtOH = 1*10^-10) 6. (4%) Why is a small amount of MgY2- often added to a water specimem tht is to be titrated for hardness? 7. (12%) Consider the titration of 50.0mL of 1.00*10^-3M Zn2+ with 1.00*10^-3M EDTA at pH10.00 in the presence of 0.10M NH3 (This is the concentration of NH3. There is also NH4+ in the solution). Find pZn2+ after addition of 50.0 and 60.0mL of EDTA. (Note: αY4-= 0.30 at pH10.00; Formation constants for the complexes Zn(NH3) 2+(β1= 10^2.18), Zn(NH3)2 2+(β2= 10^4.43) Zn(NH3)3 2+(β3= 10^6.74), Zn(NH3)4 2+(β4= 10^8.70); Formation constant for ZnY2- is 10^16.5.) 8. (12%) Calamine, which is used for relief of skin irritations, is a mixture of zinc and iron oxides. A 1.022g sample of dried calamine was dissloved in acid and diluted to 250.0mL. Potassium fluoride was added to a 10.00mL aliquot of the diluted solution to mask the iron, after suitable adjustment of the pH, Zn2+ consumed 38.71mL of 0.01294M EDTA. A second 50.00mL aliquot was suitably buffered and titrated with 2.40mL of 0.002727M ZnY2- solution. Calculate the percentages of ZnO and Fe2O3 in the sample. (MW: ZnO, 81.409; Fe2O3, 159.688) 9. (10%) (a) Show that when weak base, B, is titrated with a strong acid, the Gran function is 1 γB Va*10^(+pH) = (----*-------)(Ve - Va) Ka γBH+ where Va is the volume of strong acid and Ka is the acid dissociation constant of BH+. (b) What is the advantage of Gran plot compared with other methods for the end point determination? 10. (12%) Neutral lysine can be written HL. The other froms of lysine are H3L 2+, H2L+, and L-. The isoelectric point is the pH at which the average charge of lysine is 0. Therefore, at the isoelectric point, 2[H3L 2+] + [H2L+] = [L-]. Use the condition to calculate the isoelectric pH of lysine. (pKa1(COOH)= 1.77, pKa2(α-NH3)= 9.07, pKa3(ε-NH3)= 10.82) 11. (10%) Please describe how isoelectric focusing works for the analysis of a mixture of proteins. --

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