The pKa of acid-base indicators and the influence of colloidal systems

Química Nova

Previdello, Bruno Alarcon Fernandes¹  Souza, Vagner Roberto de¹  Carvalho, Fernando Rodrigues de¹  Tessaro, André Luiz¹  Hioka, Noboru¹  Universidade Estadual de Maringá, Maringá, Brasil¹ 

关键词: pKa;    acid-base indicator;    colloidal systems.;   

DOI  :  10.1590/S0100-40422006000300032

学科分类：化学（综合）

来源: Sociedade Brasileira de Quimica

【 摘 要 】

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.

【 授权许可】

Unknown