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Doctoral Thesis
DOI
10.11606/T.46.2018.tde-23072018-152156
Document
Author
Full name
Ruth Granhen Tavares
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 1981
Supervisor
Title in Portuguese
Estudos potenciométricos e de solubilidade no sistema iodo/iodeto. Desenvolvimento de método de cálculo de constantes de equilibrio
Keywords in Portuguese
Iodo
Potenciometria
Abstract in Portuguese
Apresentamos uma revisão bibliográfica sobre a formação de complexos no sistema iodo/iodeto. Efetuamos uma apreciação geral sobre métodos de cálculo de constantes de equilibrio em sistemas mononucleares, incluindo os métodos desenvolvidos neste Instituto de Química. Desenvolvemos uma sistemática de cálculo de constantes de equilibrio de complexos mononucleares, baseada no princípio dos mínimos quadrados, a qual é um aperfeiçoamento de uma sistemática anteriormente proposta pelo grupo de trabalho. Estudamos o sistema iodo/iodeto em meio homogêneo, através de medidas de potencial, evidenciando duas espécies mononucleares, I-3 e I2-4, com as seguintes constantes de formação, obtidas a 25ºC, e condições de força iônica 1,0 M, mantida com perclorato de sódio: [Ver esquema no PDF] Efetuamos estudos em meio heterogêneo, na mesma temperatura e condições de força iônica, com a fase solida em equilíbrio com íons iodeto. Através de medidas de potencia1 e de solubilidade, evidenciamos quatro especies binucleares: I-5, I-7, I-9 e I2-6. Combinando os dados obtidos em meio homogêneo e em meio heterogêneo obtivemos os valores das constantes de formação dessas espécies binucleares: [Ver esquema no PDF] A obtenção desses valores envolveu uma série de recursos de cálculo, processos de ensaio e erro e considerações de diversas hipóteses de tratamento de dados. Foram considerados outros equilíbrios correlatos e ainda perspectivas de trabalhos futuros. Medidas de solubilidade de iodo em soluções de brometo levaram à evidência da espécie I2Br-.
Title in English
Potentiometric and solubility studies in the iodine / iodide system. Development of method of calculating equilibrium constants
Keywords in English
Iodine
Potentiometry
Abstract in English
A bibliographie review on complex formation at the iodine/iodide system is presented. An outline and discussion about calculation of equilibrium constant was considered, including those methods developed at this Chemistry Institute. A systematie approach to calculate equilibrium constants from potentiometric data was developed, on basis of the use of the least square treatment of data. This procedure is an extension of former studies in this group of work. The iodine/iodide system was studied in a homogenium aqueous medium, at 25,00C, and ionie strength 1,0 M, held with NaClO4. The following final results were obtained, for the constants of the mononuclear species: [See squeme on PDF] A series of measurements were carried out in a heterogenium medium where solid iodine was in equilibrium with iodide ions in the working solutions. The eombination of such solubility data with the potentiometric ones lead to evaluate the presence of the following binuclear species: I-5, I-7, I-9 e I2-6. The following formation constant were determined at the conditions above mentioned: [See squeme on PDF] To obtain this formation constant several strategies were used as to solve a cumbersome puzzle, with several hypothesis being worked out and checked. Other related equilibria were considered as well as prospect for future work. Measurements of the solubility of iodine in bromide solutions lead to evidence of I2Br- specie.
 
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Publishing Date
2018-07-23
 
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