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2006
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In the Laboratory
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Introduction of Differential Scanning Calorimetry in a General Chemistry Laboratory Course: Determination of Molar Mass by Freezing Point Depression
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Ronald D'Amelia, Thomas Franks, and William F. Nirode
Department of Chemistry, Hofstra University, Hempstead, NY 11549-0151
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October 2006
Vol. 83 No. 10
p. 1537
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| Abstract |
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In many first-year general chemistry undergraduate courses, colligative properties of solutions are commonly discussed. However, even though these colligative properties are discussed in class they are infrequently reinforced in the general chemistry laboratory setting with actual examples and experiments. There have been experiments done in general chemistry laboratories for the determination of molar mass by freezing point depression using classical methodology. Today, it has become increasingly important to incorporate modern techniques and instrumentation into the general chemistry curriculum to provide a more hands-on and meaningful learning environment for the general chemistry students. This enables the reinforcement of subjects and concepts from the lecture into the laboratory. Differential scanning calorimetry (DSC) is a rugged, easy-to-use instrumental method for the determination of various thermodynamic properties. The work described herein incorporates DSC to determine the molar mass of an unknown by freezing point depression. Cyclohexane is used as the pure solvent and the molal freezing point depression constant, kfp, is determined with good agreement to the reported literature value. Three nonvolatile organic hydrocarbons are used as unknowns and their molar masses are determined within a range of 2–10% error from their accepted values.
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| Supplement |
Instructor notes, student handouts, fact sheet on thermal analysis, and safety precautions using the DSC are available.
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| More Information |
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Citation |
D'Amelia, Ronald; Franks, Thomas; Nirode, William F. J. Chem. Educ. 2006 83 1537.
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Keywords |
Calorimetry / Thermochemistry; First-Year Undergraduate / General; Hands-On Learning / Manipulatives; Instrumental Methods; Laboratory Instruction; Physical Chemistry; Solutions / Solvents; Thermal Analysis
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History |
Created:
Last Updated: |
8/23/2006
8/28/2006
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 Caution! | | Experiments, laboratory exercises, lecture demonstrations, and other descriptions of the use of chemicals, apparatus, instruments, computers, and computer interfaces are presented in the Journal of Chemical Education as illustrative of new or improved ideas or concepts in chemistry instruction and are directed at qualified teachers. Although every effort is made to assure and encourage safe practices and safe use of chemicals, the Journal of Chemical Education cannot assume responsibility for uses made of its published materials. Many chemicals are hazardous. Precautions for the safe use of hazardous chemicals and directions for their proper disposal are described in the Material Safety Data Sheets and on the labels. We strongly urge all those planning to use materials from our pages to make choices and to develop procedures for laboratory and classroom safety in accordance with local needs and situations. |
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