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Bulk Gas‐Phase Acidity
Author(s) -
Himmel Daniel,
Goll Sascha K.,
Leito Ivo,
Krossing Ingo
Publication year - 2012
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201104025
Subject(s) - gas phase , bar (unit) , chemistry , proton , acid–base reaction , gibbs free energy , base (topology) , inorganic chemistry , work (physics) , weak base , thermodynamics , physics , mathematics , nuclear physics , mathematical analysis , meteorology
The capability of a gaseous Brønsted acid HB to deliver protons to a base is usually described by the gas‐phase acidity (GA) value of the acid. However, GA values are standard Gibbs energy differences and refer to individual gas pressures of 1 bar for acid HB, base B − , and proton H + . We show that the GA value is not suited to describe the bulk acidity of a gaseous acid. Here the pressure dependence of the activities of HB, H(HB) n + , and B(HB) m − that result from gaseous autoprotolysis have to be considered. In this work, the pressure‐dependent absolute chemical potential of the proton in the representative gaseous proton acids CH 4 , NH 3 , H 2 O, HF, and HCl was worked out and the general theory to describe bulk gas phase acidity—that can directly be compared with solution acidity—was developed.