課程名稱︰物理化學二 課程性質︰必修 課程教師︰吳嘉文 開課學院：工 開課系所︰化工系 考試日期（年月日）︰2009/04/30 考試時限（分鐘）：110 是否需發放獎勵金：是 （如未明確表示，則不予發放） 試題 : Second Midterm Exam of Physical Chemistry April 30th, 2009 1. (15%) The resistance of aluminum is 9x10-3 ohm. Assume the current is 1.25 A. (5% for each) (a) Calculate the potential drop across a piece of aluminum wire that is 2.0 mm in diameter and 1.0 m long. (b) Calculate the conductance (G) of the aluminum wire described in (a). (c) Calculate the electrolytic conductivity (κ) of the aluminum wire described in (a). 2. (40%) (a) The molar ionic conductivities at infinite dilution are 7.352 x 10-3 (S m2 mol-1) for K+ and 7.634 x 10-3 (S m2 mol-1) for Cl-. Calculate Λο for KCl from these data. (10%) (b) Using the Λο value of KCl from (a), and the Λο values for HCl is 4.261 x 10-2 (S m2 mol-1) and for K(CH2ClCOO) is 1.132 x 10-2 (S m2 mol-1). Calculate the value of the molar conductivity at infinite dilution for monochloroacetic acid (i.e., CH2ClCOOH). (Hint: monochloroacetic acid is a weak electrolyte) (10%) (c) Calculate the Ka for CH2ClCOOH when the concentration of CH2ClCOOH is 1.323 x 10-3 M. The Λ value at such concentration is 2.46 x 10-2 (S m2 mol-1). (10%) (d) Explain the Ostwald’s dilution law by using the example in (d). (10%) 3. (25%) A solution of LiCl was electrolyzed in a Hittorf cell. After a current of 0.9 A had been passed for 2 h, the mass of LiCl in the anode compartment had decreased by 0.973 g. The mass of LiCl is 42.4 g. (a) Explain (t+/t-) = (amount lost from anode compartment/amount lost from cathode compartment) (5%) (b) Calculate the transport numbers of the Li+ and Cl- ions. (10%) (c) If Λο(LiCl) is 115 ohm-1 cm2 mol-1, what are the molar ionic conductivities and the ionic mobilities. (10%) 4. (20%) The solubility product of barium sulfate is 9.2 x 10-11 mol2 dm-6. Assume the DHLL to apply. (a) Calculate the solubility in an aqueous solution containing 0.1 M NaNO3 and 0.2 M Zn(NO3)2. (B = 0.51 mol-1/2 dm3/2)(10%) (b) Is (b) a salting in or salting out effect? (10%) --

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