"Modeling Stratospheric Ozone Kinetics with Mathcad, Part I: The Chapman Cycle" enables students to apply undergraduate-level physical chemistry directly to a real chemical problem in a guided-inquiry setting. The four-step Chapman cycle of stratospheric ozone reactions is used to introduce numerical solutions of complex rate laws and kinetic modeling. This document is written specifically to be accessible to novice Mathcad users and has been employed to introduce kinetics in the first weeks of undergraduate physical chemistry, immediately following completion of the Mathcad tutorial. Students learn how to define initial species concentrations and rate constants, enter the set of differential rate equations as a matrix for use with a built-in differential equation solver, and finally generate and graph species concentration profiles over specified time intervals. Along the way, they apply a majority of the chemical kinetics concepts taught in standard texts (using first-, second-, and third-order rate constants, writing differential rate laws for each of the species appearing in a chain reaction mechanism, investigating temperature dependence with Arrhenius and other models, and handling photolysis rate constants.) Photostationary state concentrations are calculated using a simultaneous equation solver. Specific variables explored through exercises in this document include temperature, total pressure, initial component concentrations, and rate constants.

Figure 1. Ozone concentration as a function of time using the Chapman cycle from OzoneModelingPartI.mcd.