Kinetic study of the disproportionation of tin monoxide

The disproportionation reaction kinetics of tin monoxide at 723 K was studied by Mössbauer spectroscopy. The kinetic parameters of the reaction were obtained by objective data processing of the Mössbauer spectra, treating the data matrix with the Single Value Decomposition procedure that, in addition, yields the spectrum of the intermediate oxide. The procedure was applied on the assumptions that the f-factors of Sn(II) and Sn(IV) atoms belonging to the intermediate oxide are equal to those of Sn(II) and Sn(IV) atoms of SnO and SnO2, respectively, that the stoichiometry of the intermediate oxide is Sn3O4, and that the disproportionation proceeds by a set of two successive first order reactions described by the sequence SnO→intermediate oxide→SnO2. The kinetic rate constants obtained for the first and second reactions were k1=2.47×10−4 s−1 and k2=1.13×10−5 s−1, respectively. The time-profile of the mole fraction of each component in partially reacted samples shows that at 723 K, the intermediate accumulates in the time bracket between ca. 100–1000 min.