Agreement, Complement, and Disagreement to “Why Are Some Reactions Slower at Higher Temperatures?”

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In the article “Why Are Some Reactions Slower at Higher Temperatures?” published in this Journal, Revell and Williamson explained, from the enthalpic and entropic aspects, why an A + B → P reaction may proceed more slowly at higher temperatures via an A + B ↔ C → P mechanism using the pre-equilibrium approximation. Their explanation is convincing but may be too abstract for undergraduate physical chemistry students to understand fully. In this communication, a numerical implementation and graphical demonstrations of their explanation are provided for students to use to “see” for themselves a negative activation energy. Although Revell and Williamson perfectly explained the negative temperature dependence of the A + B ↔ C → P reaction rate, great caution must be exercised when their explanation is applied to interstellar chemistry where the pre-equilibrium approximation may be invalid and statistical thermodynamics functions may be ill-defined.


This article was originally published in Journal of Chemical Education. The full-text article from the publisher can be found here.

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Journal of Chemical Education


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