O pKa de indicadores ácido-base e os efeitos coloidais
AUTOR(ES)
Previdello, Bruno Alarcon Fernandes, Carvalho, Fernando Rodrigues de, Tessaro, André Luiz, Souza, Vagner Roberto de, Hioka, Noboru
FONTE
Química Nova
DATA DE PUBLICAÇÃO
2006-06
RESUMO
An experiment is proposed that can be included in undergraduate courses of chemistry. The subject is the acidity of organic compounds, which are employed as pH indicators, particularly in acid-base titrations. The indicators used are methyl orange, bromophenol blue and bromocresol green in aqueous medium. The influence of colloidal systems on the equilibrium is evaluated by the pKa. The colloids employed are surfactants like sodium dodecyl sulfate, cetyl-trimethylammonium bromide and a polymeric non-ionic F127 (pluronics). The effect of stabilization promoted by the system on the acidic or basic structureof the indicator establishes the action mechanism of the colloid on the pKa values.
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