Hexachlorotellurate(IV) hydrolysis equilibria in hydrochloric acid. Measurement by Raman and 125 Te NMR spectroscopy and a reconsideration of earlier spectrophotometric results
1991; NRC Research Press; Volume: 69; Issue: 6 Linguagem: Inglês
10.1139/v91-144
ISSN1480-3291
Autores Tópico(s)Crystal Structures and Properties
ResumoSolutions of TeO 2 (0.001 M) in HCl over a range of concentrations are shown to contain TeCl 2 (OH) 2 in addition to TeCl 6 2− and TeCl 4 (OH) − . The hydrolysis constants for TeCl 6 2− and TeCl 4 (OH) − have been determined from a reconsideration of earlier UV-visible spectrophotometric results (1)[Formula: see text]The hydrolysis constants have also been determined by quantitative Raman spectroscopy (K 1 = 2.21 (± 0.16) × 10 4 M 3 ; K 2 = 442 ± 57 M 3 ). The agreement between K 2 determined by the two methods is good but K 1 from spectrophotometry is much larger than that from Raman studies. This disagreement is attributed to ion-pairing which will be significant at the concentration at which the Raman measurements were made (c(TeO 2 ) = 0.50 M). The hydrolysis constant for TeCl 6 2− was also determined from the 125 Te NMR spectra of TeO 2 /HCl solutions, which consisted of one signal, indicating rapid Te exchange between all species. The hydrolysis constant, determined in this way (K 1 = 1.92 (± 0.07) × 10 4 M 3 ) was also low compared to that determined from spectrophotometry. Key words: solution, equilibria, tellurium, hydrochloric acid, Raman spectroscopy, 125 Te NMR spectroscopy, UV–visible spectrophotometry.
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