翻訳と辞書
Words near each other
・ "O" Is for Outlaw
・ "O"-Jung.Ban.Hap.
・ "Ode-to-Napoleon" hexachord
・ "Oh Yeah!" Live
・ "Our Contemporary" regional art exhibition (Leningrad, 1975)
・ "P" Is for Peril
・ "Pimpernel" Smith
・ "Polish death camp" controversy
・ "Pro knigi" ("About books")
・ "Prosopa" Greek Television Awards
・ "Pussy Cats" Starring the Walkmen
・ "Q" Is for Quarry
・ "R" Is for Ricochet
・ "R" The King (2016 film)
・ "Rags" Ragland
・ ! (album)
・ ! (disambiguation)
・ !!
・ !!!
・ !!! (album)
・ !!Destroy-Oh-Boy!!
・ !Action Pact!
・ !Arriba! La Pachanga
・ !Hero
・ !Hero (album)
・ !Kung language
・ !Oka Tokat
・ !PAUS3
・ !T.O.O.H.!
・ !Women Art Revolution


Dictionary Lists
翻訳と辞書 辞書検索 [ 開発暫定版 ]
スポンサード リンク

entropy of activation : ウィキペディア英語版
entropy of activation
In chemical kinetics, the entropy of activation of a reaction is one of the two parameters (along with the ''enthalpy of activation'') which are typically obtained from the temperature dependence of a reaction rate constant, when these data are analyzed using the Eyring equation. The standard entropy of activation is symbolized ΔS and equals the change in entropy when the reactants change from their initial state to the activated complex or transition state (Δ = change, S = entropy, ‡ = activation). It determines the preexponential factor A of the Arrhenius equation for temperature dependence of reaction rates. The relationship depends on the molecularity of the reaction: for reactions in solution and unimolecular gas reactions A = (ekBT/h) exp(ΔS/R), while for bimolecular gas reactions A = (e2kBT/h) (R'T/p) exp(ΔS/R). In these equations e is the base of natural logarithms, h is the Planck constant, kB is the Boltzmann constant and T the absolute temperature. R' is the ideal gas constant in units of (bar
*L)/(mol
*K). The factor is needed because of the pressure dependence of the reaction rate. R' = 8.3145
* 10^-2 (bar
*L)/(mol
*K). 〔Laidler, K.J. and Meiser J.H. ''Physical Chemistry'' (Benjamin/Cummings 1982) p.381-2 ISBN 0-8053-5682-7〕
The value of ΔS provides clues about the molecularity of the rate determining step in a reaction, i.e. whether the reactants are bonded to each other, or not. Positive values suggest that entropy increases upon achieving the transition state, which often indicates a dissociative mechanism in which the activated complex is loosely bound and about to dissociate. Negative values for ΔS indicate that entropy decreases on forming the transition state, which often indicates an associative mechanism in which two reaction partners form a single activated complex.〔James H. Espenson ''Chemical Kinetics and Reaction Mechanisms'' (2nd ed., McGraw-Hill 2002), p.156-160 ISBN 0-07-288362-6〕
==References==


抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)
ウィキペディアで「entropy of activation」の詳細全文を読む



スポンサード リンク
翻訳と辞書 : 翻訳のためのインターネットリソース

Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.