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  Home > JCE Print > Journal of Chemical Education > Issues > 2003  > December  >
In the Laboratory
Advanced Chemistry Classroom and Laboratory
Spectroscopic Monitoring of the Heterogeneous Catalytic Decomposition of Gaseous Ammonia
Jonathan D. Fischer and James E. Whitten
Department of Chemistry, University of Massachusetts-Lowell, Lowell, MA 01854
Cover
December 2003
Vol. 80 No. 12
p. 1451
Abstract
New generations of electro–optic devices now make possible the relatively low-cost spectroscopic detection of many molecules. As part of our effort to cost-effectively modernize the physical chemistry laboratory curriculum, a 2.2 micron light-emitting diode and photodiode detector have been used to detect gaseous ammonia by infrared spectroscopy. A linear plot of absorbance versus pressure is observed when a stainless steel chamber, constructed from off-the-shelf vacuum hardware and fitted with two glass windows, is filled with ammonia. By installing a tungsten filament in the chamber, the heterogeneous catalytic decomposition of ammonia by a hot metal surface may be monitored. This is a classic example of a reaction that follows zero-order kinetics at relatively high ammonia pressures and moderate temperatures. Linear plots of absorbance versus time during the initial stages of the reaction and the observed independence of slope on ammonia pressure are consistent with a zero-order rate law.
Supplement
Instructions for the students, details related to the construction of the apparatus, and a parts list are available.
*  Contents JCE2003p1451W.doc (Microsoft Word)
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More Information
*  Citation
 Fischer, Jonathan D.; Whitten, James E. J. Chem. Educ. 2003 80 1451.
*  Keywords
 Catalysis; Gases; IR Spectroscopy; Kinetics; Laboratory Equipment / Apparatus; Laboratory Instruction; Physical Chemistry; Surface Science
*  History
 Created:
Last Updated:		 October 31, 2003
February 28, 2005
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