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

Quimica nova

Previdello, Bruno Alarcon Fernandes¹  Souza, Vagner Roberto de¹  Carvalho, Fernando Rodrigues de¹  Tessaro, André Luiz¹  Hioka, Noboru¹ 

[1] Universidade Estadual de Maringá, Maringá, Brasil

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 experimentis proposed that can be included in undergraduate courses of chemistry. Thesubject 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 colloidalsystems on the equilibrium is evaluated by the pKa. The colloidsemployed are surfactants like sodium dodecyl sulfate, cetyl-trimethylammoniumbromide and a polymeric non-ionic F127 (pluronics). The effect of stabilizationpromoted by the system on the acidic or basic structureof the indicator establishesthe action mechanism of the colloid on the pKa values.

【 授权许可】

CC BY