209exam2 - CHEM 209 Final Exam 2/20/06 NAME: 1. (20 POINTS)...

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Unformatted text preview: CHEM 209 Final Exam 2/20/06 NAME: 1. (20 POINTS) Suppose a student is determining the total base content of an antacid tablet by perfonning a back titration. He/she weighs out a 0.3022-gram portion of a tablet whose total weight is 1.6335 grams, dissolves this in exactly 30.00mL of deionized water, and then adds exactly 2000 mL of 0. 1000M HCl in order to bring the pH down to 2.21 This solution is then carefully back-titrated with 0.1-050M NaOH, with 3.77 mL required to reach the equivalence point. Calculate the total base content (i.e., the number of mmoles of base contained) of the antacid tablet. SHOW 'ALL WORK CLEARLY. (Formula weight of HCl = 36.46 gram/mole; formula weight of NaOH = 40.00 gram/mole). 2. (30 POINTS)- (a) Write the equation for Beer’s Law and define all the terms (including the correct units for each term). _ i _ (b) The absorbence of a 1.0 x 10le Fe(l,10-phen)32+ solution is measured at a wavelength of 5 ] 0 nm and found to be 0400. What is the transmittance of this solution? SHOW YOUR WORK. ________.__._____..__..._-WW._._.T_...._.____..., . .. (c) Suppose the solution in part (b) is diluted with deionized water by a factor of 2. What are the absorbance and transmittance of the diluted solution? SHOW YOUR WORK. 3. (14 POINTS) Sketch the shape of the titration curves expected for the following titrations: (a) BC] with NaOH pH mL NaOI-I (b) KI-IP with NaOH ' pH mL NaOH 4. (16 POINTS) What quantities are plotted on the x— and y—axes of: x»axis (a) a chromatogram? (b) a calibration curve? y-aXis Huawhfiw .r‘ w W 5. 0 POINTS) Define the term “retention time”. What'is its principal use in GO analysis? - 6. POINTS) Write the equilibrium constant expressions for the folloWing balanced ' chemical reactions: _ (a): 2Mn04' + 5H3A303 + 6H+ —-——> 2Mn2+ +5H3AsO4 +3H20 K: (b) H3P04 + 3H20 --——> 9043' + 3H30+ K = BO? _[_]S QUESTION [10 POINTS} Suppose that your teaching assistant, while working on ‘s/her MS degree in Chemistry, discovers a new compound X which might be used to remove mercury ng (which is toxic) from contaminated water samples according to the following balanced reaction; Hg“ + 2 X a? tax? The TA tries to determine the numerical value of the equilibrium constant by mixing 50 ml of 0.10M Hg With 50 ml of 0.20M X, allowing the reaction to occur and reach equilibrium, and then measuring the resulting Hng2+ concentration as 0.045M. Help your TA to get his/her degree by completing the calculation needed to evaluate 'K for the above reaction. SHOW YOUR WORK. . W—.m__mvmW—_q___._. ._......_._.H.... ‘ . . ...
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This note was uploaded on 09/12/2008 for the course CHEM 209 taught by Professor Greg during the Spring '07 term at University of Louisville.

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209exam2 - CHEM 209 Final Exam 2/20/06 NAME: 1. (20 POINTS)...

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