Comment on the evaluation of the arrhenius parameters by the least squares method

✍ Scribed by R. J. Cvetanovic; D. L. Singleton

• Publisher: John Wiley and Sons
• Year: 1977
• Tongue: English
• Weight: 450 KB
• Volume: 9
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550090315

✦ Synopsis

Abstract

Arrhenius parameters are frequently evaluated incorrectly by applying the least squares method to the logarithmic form of the Arrhenius equation without simultaneously transforming the statistical weights as required for the change of variable from k to ln k. This has been mentioned briefly in an earlier paper. In the present communication the correct procedures are discussed and illustrated by several examples of evaluations. In particular, Arrhenius parameters calculated by the Taylor series expansion of the exponential form of the Arrhenius equation are compared with those calculated from the logarithmic form, using an exact and two approximate transformations of the statistical weights. The comparisons indicate thatthe preferred procedure for obtaining Arrhenius parameters is either the Taylor series method or the logarithmic method with proper transformation of the experimentally determined statistical weights of the rate constants k~i~. The common approximation of assuming equal statistical weights of ln k~i~ when the logarithmic form of the Arrhenius expression is used is shown not to be always appropriate, and reasons forthis are given.