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）︰2008/10/20 考试时限（分钟）：120分钟 是否需发放奖励金：是 （如未明确表示，则不予发放） 试题 : Analytical Chemistry (Total: 113%) 1. Explain the difference between (21%, a-e: 3% for each, f: 6%) (a) a colloidal and a crystalline precipitate (b) specific and selective precipitating reagent (c) sample standard deviation and population standard deviation (d) random and systematic error (e) coefficient of variation and standard deviation (f) Volhard method and Fajans method in the chloride determination 2. Explain the term "spike recovery". The recovery is often less than 100%, why? (6%) 3. State why standard additions and internal standards, instead of a calibration curve, are desirable, and why? How to choose and appropriate internal standard? (10%) 4. How is a control chard used? State six indeications that a process is going out of control. (6%) 5. The solubility product Ksp for the silver salt AgX is 4.0(±0.4)*10^-8. What is the molar solubility of AgX in water? (6%) 6. Neglecting any effects caused by volume changes, would you expect the ionic strength to (1)increase, (2)decrease, or (3)remain essentially unchanged by the addition of NaOH to a dilution of (a) magnesium chloride [Mg(OH)2(s) forms]? (b) hydrochloric acid? (c) acetic acid? Please give the reason for your choice. (9%) 7. Find the molar solubility S of silver chloride in 0.04M sodium nitrate. The o activity constant for Ksp = 1.765*10^-10 (10%) 8. A chemist obtained the following data for percent lindane in the triplicate analysis of an insecticide preparation: 7.47, 6.98, 7.27. Calculate the 90% confidence limit for the mean of the three data, assuming that (a) the only information about the precision of the method is the precision for the three data. (b) on the basis of long experience with the method, it is believed that s→σ =0.28% lindane. (10%) 9. From previous measurements of a low concentration of analyte, the signal detection limit was estimated to be in the low nanoampere range. Signals from seven replicate samples with a concentration about three times the detection limit were 5.0, 5.0, 5.2, 4.2, 4.6, 6.0, and 4.9nA. Reagent blanks gave values of 1.4, 2.2, 1.7, 0.9, 0.4, 1.5, and 0.7 nA. The slope of the calibration curve for higher concentrations is m = 0.229nA/μM. (a) Find the signal detection limit and the minimum detectable concentration. (b) What is the concentration of analyte in a sample that gave a signal of 7.0nA? (10%) 10. How to determine the protein content in the milk with Kjedaho method? (15%) 11. The dissociation constant Kd for AgCl in aqueous solution has a value of 5.0*10^-4, its solubility product is 1.82*10^-10. Calculate the solubility of silver chloride in water and the percent of the dissolved solute that is present as the undissociate comound. (10%) (附有表 "Values of Student's t") --

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