The author replies to Hanson.
I would like to thank Robert Hanson for his kind remarks concerning my recent article (1). The print version of the article deals largely with teaching entropy analysis to the first-year high school level with some material intended for more advanced students. A large portion of the material presented in the supplement is for advanced students (classes) and teacher enhancement.In the first-year course, I do not present concentration effects or pressure effects. Pressure and concentration effects are discussed in the supplement on pages 17–19 (S = S° – R ln P and ∆rS = ∆rS° – R ln Q), as they are much more advanced topics. Additionally, on page 19 of the supplement, Q < K is discussed as a condition for the spontaneous conversion of reactants to products and likewise, Q > K is a condition for the spontaneous conversion of products into reactants. There is a problem with the symbol “∆Suniv” as it does not indicate whether the reactive system is in standard state or not. If the system is in standard state, then the numerical value for ∆Suniv can be used to directly calculate K, otherwise not. The use of ∆S°univ to denote that the reactive system is under standard state conditions is not ideal, as there are no standard states for the universe. Craig (2) has stated that there is a degree of “awkwardness” associated with the use of the standard state designation in this way. Unfortunately, this led to the use of ∆Suniv = –R ln K and –T∆Suniv = ∆rG°. Perhaps a new symbol could be devised, such as, ∆Suniv(sys°). Literature Cited- Bindel, T. H. J. Chem Educ. 2004, 81, 1585.
- Craig, N.C. Entropy Analysis; VCH: New York, 1992.
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