课程名称︰普化甲下 课程性质︰必 课程教师︰佘瑞琳 开课学院：理学院 开课系所︰化学系 考试日期（年月日）︰4/20/2010 考试时限（分钟）：130 是否需发放奖励金：yes pls （如未明确表示，则不予发放） 试题 : II. problems(60%) 1. For the following reaction, Fe(OH)3(s) + 3H+(aq) <==> Fe3+(aq) +3H2O(l), K = 9.1 E3. (a) Write the equilibrium constant expression (in activities). (b) Compute the equilibrium cpmcentration for Fe3+ at pH=7. (4%) 2. The following titration curve was obtained as part of a general chemistry labatory exoeriment for an unknown that weighted 0.8g. The titrant was either a 0.2 M strong base or acid. (both unknown and titrant are taken as solo) (a) Estimate the molar mass of the unknown (b) EWstimate its ionization constant (4%) Figure: | |- | - pH | - - -| | |- | ------- |----------------- ml of titrant (当量点在50 ml) 3. For a solution that is 0.275 M CH3CH2COOH (propionic acid Ka= 1.3 E-5) and 0.892 M HI, calculate (a) [H3O+] (b) [CH3CH2COO-] (c)[I-] (6%) 4. A 25.00 ml sample of 0.001 M C6H5COOH (Ka = 6.3 E-5) is titrated with 0.01 M Ba(OH)2. Calculate the pH (a) of the initial acid solution (b) after the additoin of 6.25 ml titrant (c) at the equivalence point (d) Which of the following indicator would you choose for the titration ,methyl red(pKa=5), or phenolphthalein(pKa=8)? (8%) 5. To precopitate as Ag2S(s), all the Ag+ present in 338 ml if a saturated solution of AgBrO3 requires 30.4 ml of H2S(g) meansured at 23 oC and 748mmHg Calculate Ksp of AgBrO3(s). (6%) 6. What is the standard molar entropy for the vaporization of water at 373K given that the standard enthalpy of vaporization is 40.7 kJ/mol? Why it's different from Trouton's rule, that for many liquids at their normal b.p., the standard molar entrophy of vaporization has a value about 87J/MOL-K? (4%) 7. Consider the reaction: 2SO2(g) + O2(g) => 2SO3(g), carried out at 25 oC,1atm (a) Calculate standard delta enthalpy, entropy, and free energy. (b) Calculate the equilibrium constant, K, for the reaction. (c) Is the reaction spontaneous or not at standatd state? (d) How is the rate of the reaction, fast or slow? (e) What is the value of free energy when the reaction is at equilibrium? (10%) Substance standard enthalpy of formation(kJ/mol) standard entropy(J/mol-K) =========================================================================== SO2(g) -297 248 SO3(g) -396 257 O2(g) 0 205 8. For the Haber process, the standard enthalpy and entropy is -92.38kJ/mol and -198.3J/mol-K, respectively. (a) Is the reaction endothermic or exothermic? (b) Does the entropy of system increase or decrease? (c) At 500 oC and standard states, the forward reaction is spontaneous or not? (d) Calculate the equilibrium constant at 500 oC. (8%) 9. The P(32,15) is the radioisotope of phosphorus that emits beta particle with a half-lifeof 14.3 days. (a) Write the balanced nuclear equation. (b) What is the decay constant for P(32), expressed in unit s? (c) What is the activity of a 1.00 mg sample of P(32) (that is how many stoms disintegrate per second)? (d) Approximately what mass of P will reamin in the original sample (1.00 mg) after 57 days? (e) What will be the rate of radioactive decay after 57 days? (10%) exam ends here. -- 花退残红青杏小，燕子飞时，绿水人家绕。枝上柳棉吹又少，天涯何处无芳草。 墙里秋千墙外道，墙外行人，墙里佳人笑。笑渐不闻声渐悄，多情却被无情恼。 --

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