209dayfinal - CHEM 209 a Day Final Exam NAME 1(30 POINTS(a...

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Unformatted text preview: CHEM 209 a Day Final Exam 10/4/04 NAME: % 1. (30 POINTS) (a) Suppose that you are given the task of determining the Fe content ofa multi-vitamin tablet by forming the Fe(1,10-phen)32+ complex and measuring its absorbance. You begin by weighing out a 0.5000-gram portion of a tablet whose total weight is 2.5000 gram, transferring this portion to a lOO—mL volumetric flask, and dissolving it in IOO-mL of deionized water. You then take exactly 5.00 mL of this solution into another IOO—mL flask, add the appropriate volumes of 1,10-phen, hydroxylamine hydrochloride, and NaOAc buffer, allow it to stand for 5 minutes, and then bring the volume to exactly 100 mL with deionized water. The %T of this solution, measured at 510 nm, is 27.5%. A calibration curve, prepared from Fe(1,10-phen)32+ standards, indicates that the Fe concentration of this sample solution is 3.10 ug/tnL. Calculate the Fe content (in mg) of the multivitamin tablet. SHOW ALL WORK CLEARLY. (Atomic weight of Fe = 55.85 gram/mole) (b) What is the absorbance of the sample solution? 2. (30 POINTS) (a) Write the balanced chemical reaction that occurs during the ‘ titration of Na2C03 with HCl. (b) On the graph below, sketch the shape of the titration curve expected for this titration. M . mL HCI (c) If the Na2003 weight taken for the titration was 0.3333 gram and concentration of the HCl solution was 0.096M, calculate the equivalence point volume expected. SHOW ALL WORK CLEARLY. (Formula weights: Na2003 = 105.99 gnu/mole; HCl = 36.46 gnu/mole) 3. (20 POINTS) What quantities are plotted on the x— and y—axes of: x-axis -axis (a) a chromatogram? (b) an absorption spectrum? 4. (10 POINTS) Define the term “partition coefficient”. BONUS QUESTION (10 POINTS) What detector was used in the GC experiment? Briefly explain its operating principIe. ...
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