Dynamic and Interactive Visualization in General Chemistry: Kinetics of Dinitrogen Pentoxide Decomposition and the Ozone Hole
Scott A. Sinex Prince George's Community College
Technology has greatly enhanced the capability to present topics in general chemistry in a dynamic and interactive visual fashion and in a discovery mode. This presentation will demonstrate the use of Chime (molecular structure rendering freeware), STELLA modeling software, and an interactive Excel spreadsheet to present a kinetics activity in a guided-inquiry or discovery mode of instruction. This activity is centered on the reaction given below. The N2O5 undergoes a unimolecular reaction to N2O4 and with comparison to ether and epoxide formation; a transition state can be formulated for the decomposition. This allows for the development of the microscopic aspects of the reaction. 2N2O5 (g) 2N2O4(g) + O2 (g) 4 NO2(g) + O2 (g)
The correct structure of dinitrogen pentoxide is not easy to find, as it is incorrect in many textbooks and websites. We produced the structure using Spartan Plus, computational software, and minimized the energy using an AM1 calculation. The structure is very close to the literature values summarized in figure 2 in the Internet Journal of Vibrational Spectroscopy vol. 2/edition 1, pp. 50-56 (1998). Students must measure bond distances and bond angles using Chime plus interpret a STELLA simulation of the decomposition reaction. They will collect data to derive the rate law. An Arrhenius plot is explored using an interactive Excel spreadsheet. The basics of the STELLA model are modified from a Shodor Dinitrogen Pentoxide Simulation. The simulation runs on their web page and produces graphical results. You do not need STELLA to run this simulation. Shodor has a nice explanation for this simulation as an authentic task. This activity is part of a series called Structure and Bonding: Guided-Inquiry Activities for General Chemistry Using Chime. Links to Chime and a free run-only full demo version of STELLA can be found at the PGCC Department of Physical Sciences website along with downloadable instructions for using Excel. Click on student resources. More activities, interactive Excel spreadsheets, STELLA models, and links to great simulations and animations on the Internet can also be found on my General Chemistry I and General Chemistry II homepages. Through the use of Chime, STELLA, and Excel, conceptual understanding can be enhanced and many science process and higher-order thinking skills are strengthened. Better chemistry through technology! Presented at the Middle Atlantic Regional Meeting of the American Chemical Society at George Mason University in Fairfax, VA on 11-13 May 2002. Available with hot links at http://academic.pg.cc.md.us/~ssinex and then click on presentations.