Dehydration
of solids in different modes as a proof of their primary congruent dissociative
vaporization |
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Authors: | B V L’vov |
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Institution: | (1) Department of Analytical Chemistry, St. Petersburg State Polytechnic University, St. Petersburg, Russia, 195251 |
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Abstract: | The main purpose of this
paper is to prove the applicability of the mechanism of congruent dissociative
vaporization (CDV) to the solid-state decomposition kinetics through the comparison
of the fundamental theoretical relationship Ei/Ee=(a+b)/a resulted
from this mechanism with experiment. It has been shown that the ratios of Ei and Ee
parameters of the Arrhenius equation measured in the isobaric and equimolar
modes (in the presence and absence of H2O vapour) for
22 reactants with the general formula aSalt⋅bH2O or aOxide⋅bH2O are in agreement with
the values of (a+b)/a. The relative standard deviation is only 17% and
the correlation coefficient is close to 0.99. A probability of accidental
correlation for all set of the E parameters
taken from the literature is lower than 4⋅10–16
. This strongly supports the validity of the CDV mechanism. The problem of
stability of polyatomic molecules of inorganic salts in the gaseous state,
which are the primary decomposition products of crystalline hydrates, was
also discussed on the basis of recent mass spectroscopy studies. It was concluded
that any doubts in the applicability of the CDV mechanism as a general mechanism
of solid-state decomposition reactions are unsound. |
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Keywords: | congruent dissociative vaporization dehydration kinetics equimolar and isobaric modes gaseous molecules of salts Hertz– Langmuir approach |
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