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Visualizing the Transition State: A Hands-on Approach to the Arrhenius Equation

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Matthew S. Swanson

Department of Mathematics, Spring Arbor University, Spring Arbor, MI 49283

Deborah K. Sayers

West High School, Knoxville, TN 37919

Thomas S. Kuntzleman

Department of Chemistry, Spring Arbor University, Spring Arbor, MI 49283

J. Chem. Educ., 2007, 84 (11), p 1776

DOI: 10.1021/ed084p1776

Publication Date (Web): November 1, 2007

Abstract

An exercise is presented in which the kinetics of the irreversible "reaction" of pennies in the heads-up state to pennies in the tails-up state is simulated by a hands-on, Monte Carlo approach. In addition, the exercise incorporates a second simulation in which the irreversible "reaction" of dice with a red face uppermost to a blue face uppermost is conducted. The transition states of the reactions are assumed to be a penny that is in the process of being flipped or a die in the process of being rolled, respectively. Data collected by students who perform these simulations show that both "reactions" follow first-order decay kinetics. Arrhenius plots from these data yield activation energies comparable to assigned values and pre-exponential factors close to what would be expected based on the probability of a "reactant" achieving the correct orientation for conversion into "product". A comparison of the values obtained for the pre-exponential factors for the different simulations allows students to semi-quantitatively discuss the orientational requirement that is contained within this factor.