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Chem-3000-Prelabs-Fall-2009-Prelab-4b

# Chem-3000-Prelabs-Fall-2009-Prelab-4b - n 1 2 3 4 5 6 time...

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PRE-LABORATORY EXERCISES 8 Experiment 4 Day 2 Prelab Last ________________________________ First _____________________ Email: [email protected] cornell.edu [ ] Christina Cowman [ ] Yingchao (Alex) Yu [ ] Angela Bruneau [ ] Mon PM [ ] Tues AM [ ] Tues PM [ ] Weds PM [ ] Thurs PM The purpose of this prelab is to get you familiar with fitting data to a line — deriving both the best-fit slope and intercept as well as the standard deviation in the best-fit slope and intercept — in preparation for Experiment 5 (Gas Chromatography). You have run a reaction where A and B go to product C . Under pseudo first order conditions where reactant B is in excess and its change over time is negligible during the course of the reaction, you have followed the concentration of A as a function of time using infrared absorbance of reactant A (assume that the absorbance follows the concentration of A linearly). We have converted the absorbance data to concentration assuming this linear relationship.
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Unformatted text preview: n 1 2 3 4 5 6 time t (sec) 10 50 100 150 200 250 concentration [ A ( t )] mol L-1 0.097 0.089 0.087 0.074 0.06 0.054 error in A mol L-1 0.005 0.005 0.005 0.005 0.005 0.005 1. Using Harvey equation 13.8, ﬁt this data to a linear curve with time t on the x axis and [ A ( t )] on the y axis. Give the line equation and calculate the standard deviations for the resulting slope k 00 (Eq. 5.16) and y-intercept [ A ] (Eq. 5.17). k 00 = _______________ σ k 00 = _______________ [ A ] = _______________ σ [ A ] = _______________ 2. With 99% conﬁdence, how long should you wait to be sure that the reaction has completed? t wait = _______________ 3. If noise in the infrared spectrometer signal has greater error as absorbances approach zero, would equations 5.16 and 5.17 still be applicable? Why or why not? Cornell University Chemistry 3000 — Fall 2009 J. A. Marohn...
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