17 Jul 2010

Synthesis and Molecular Modeling of Sodium Tetrathionate

Lab Experiment

Submitted by Kim Lance, Ohio Wesleyan University
Categories
Description: 
This experiment is a computational supplement to synthesis of sodium tetrathionate described in "Macroscale Inorganic Chemistry:  A Comprehensive Laboratory Experience".*  Students will synthesize one sulfur oxyanion (tetrathionate), optimize and compute IR spectra for their synthesized product.   In addition, students will predict (using symmetry arguments) and then compute the IR vibrational modes for six additional sulfur oxyanions.  A comparison of theoretical (IR spectra), experimental (IR spectra) and computational data ( IR spectra) will aid them in determining the most in identifying the S-O vibrations in their experimental spectrum. * Szafran, Z.; Pike, R.; Singh, M. Microscale Inorganic Chemistry:  A Comprehensive Laboratory Experience; Wiley:  New York, 1991. 
Learning Goals: 
A student will be able to successfully perform a titration;

A student will be able to quantitatively synthesize a sulfur oxyanion;

A student will be able to draw the Lewis structures of a series of sulfur oxyanions;

A student will be able to determine the point groups and number of vibrational modes in a series of sulfur oxyanions;

A student will be able to use computational methods to determine the number of vibrational modes in a series of sulfur oxyanions;

A student will successfully obtain an infrared spectrum for each in a series of sulfur oxyanions;

A student will be able to interpret the infrared spectra of the sulfur oxyanions including the labeling of the vibration responsible for the frequency;

A student will be able to explain the change in the frequency with respect to the oxidation number in a series of sulfur oxyanions;

Equipment needs: 
100 mg iodine/student
1.5 g potassium iodide/student
300 mg sodium thiosulfate pentahydrate/student
1% starch solution/1 mL per student
10 mL beaker/student
25 mL beaker/student
2 mL ethanol/student
0.500 mL diethyl ether/student
Hirsch funnel/student
10 mL filter flask/student
sodium sulfate (1 mg/student for IR)
sodium sulfite(1 mg/student for IR)
sodium thiosulfate(1 mg/student for IR)
sodium bisulfite(1 mg/student for IR)
potassium peroxodisulfate(1 mg/student for IR)
sodium dithionite(1 mg/student for IR)
infrared spectrophotometer
dry potassium bromide
molecular modeling software
Time Required: 
Two or Three three-hour laboratory periods
Evaluation
Evaluation Methods: 
Our inorganic laboratory program involves a rotation through a series of four experiments – and this is one of those experiments. Each student’s laboratory notebook is collected every four weeks and graded on a grading rubric which will be added later. I have the students rotate through the experiments and rotate through the final report – either written or oral. The written report is in the format of the American Chemical Society Style Book Guidelines for submitting a paper to JACS. The oral report is in the format of an ACS national meeting where each student is introduced, given 15 minutes to talk and five minutes for questions and answers.
Creative Commons License: 
Creative Commons Licence

The VIPEr community supports respectful and voluntary sharing. Click here for a description of our default Creative Commons license.