Chem-3000-Prelabs-Fall-2009-Prelab-6c

# Chem-3000-Prelabs-Fall-2009-Prelab-6c - trochemical...

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PRE-LABORATORY EXERCISES 9 Experiment 6 Day 3 Prelab Last ________________________________ First _____________________ Email: ___________________@ cornell.edu [ ] Christina Cowman [ ] Yingchao (Alex) Yu [ ] Angela Bruneau [ ] Mon PM [ ] Tues AM [ ] Tues PM [ ] Weds PM [ ] Thurs PM The purpose of this pre-laboratory exercise is to work through the calculations for Experiment 6, Sections 6.6 and 6.7. In this exercise, you will be given data similar to that obtained during Experiment 6. You will use this data to calculate the concentration of a thiosulfate solution, the concentration of a standard ICl solution, and, ﬁnally, the iodine number of corn oil. 1. A 2.00 mL aliquot of a thiosulfate solution was titrated electrochemically at a current of 42.00 mA. The equivalence point was reached at 4 minutes and 6 seconds. Determine the molarity of the thiosulfate solution. thiosulfate concentration = _______________ M 2. A 5.00 mL aliquot of ICl was over-titrated with 22.00 mL of thiosulfate solution (standardized in question 1). An elec-
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Unformatted text preview: trochemical back-titration was conducted at a current of 42.00 mA. The electrochemical back-titration reached the equiv-alence point at 2 minutes and 37 seconds. Determine the molarity of the standard ICl solution. ICl concentration = _______________ M 3. Now that the thiosulfate and ICl solutions have been standardized, we can determine the iodine number for corn oil. A 0.1000 g samples of corn oil was reacted with 10.00 mL of the standardized ICl solution. The resulting solution was over-titrated with 20.00 mL of the standardized thiosulfate solution. An electrochemical back-titration was conducted at a current of 42.0 mA; the equivalence point was reached at 2 minutes 9 seconds. Note that the formula weight of I 2 is 253.81 g/mol while the formula weight of ICl is 162.36 g/mol. Determine the iodine number (the grams of iodine per 100 grams of oil) for the corn oil. iodine number = _______________ Cornell University Chemistry 3000 — Fall 2009 J. A. Marohn...
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## This note was uploaded on 02/11/2010 for the course CHEM 3000 at Cornell.

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