A simplified undergraduate laboratory experiment to evaluate the effect of the ionic strength on the equilibrium concentration quotient of the bromcresol green dye

A modified laboratory experiment for undergraduate students is presented to evaluate the effects of the ionic strength, I, on the equilibrium concentration quotient, K c, of the acid-base indicator bromcresol green (BCG). The two-step deprotonation of the acidic form of the dye (sultone form), as it...

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Autores principales: Rodríguez, Hernán Bernardo, Mirenda, Martín
Publicado: 2012
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00219584_v89_n9_p1201_Rodriguez
http://hdl.handle.net/20.500.12110/paper_00219584_v89_n9_p1201_Rodriguez
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spelling paper:paper_00219584_v89_n9_p1201_Rodriguez2023-06-08T14:43:57Z A simplified undergraduate laboratory experiment to evaluate the effect of the ionic strength on the equilibrium concentration quotient of the bromcresol green dye Rodríguez, Hernán Bernardo Mirenda, Martín A modified laboratory experiment for undergraduate students is presented to evaluate the effects of the ionic strength, I, on the equilibrium concentration quotient, K c, of the acid-base indicator bromcresol green (BCG). The two-step deprotonation of the acidic form of the dye (sultone form), as it is dissolved in water, yields suitable hydronium concentration in the solution to carry out the experiment successfully and avoids the use of any buffer solution to fix the hydronium concentration of the media. The 95% confidence interval for the slope parameter (-2.08 ± 0.13), obtained from the linear fit of pK c versus √I/ (1 + 2.30√I) plot, contains the theoretical value of -2.04 predicted by the Debye-Hückel extended law. From the intercept, a value for the equilibrium dissociation constant of BCG, pK = (4.91 ± 0.02), is obtained, showing a reasonable agreement with literature data. The simplification makes it possible for students to complete the experiment in the course of an ordinary 3-h laboratory session. © 2012 The American Chemical Society and Division of Chemical Education, Inc. Fil:Rodríguez, H.B. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Mirenda, M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 2012 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00219584_v89_n9_p1201_Rodriguez http://hdl.handle.net/20.500.12110/paper_00219584_v89_n9_p1201_Rodriguez
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
description A modified laboratory experiment for undergraduate students is presented to evaluate the effects of the ionic strength, I, on the equilibrium concentration quotient, K c, of the acid-base indicator bromcresol green (BCG). The two-step deprotonation of the acidic form of the dye (sultone form), as it is dissolved in water, yields suitable hydronium concentration in the solution to carry out the experiment successfully and avoids the use of any buffer solution to fix the hydronium concentration of the media. The 95% confidence interval for the slope parameter (-2.08 ± 0.13), obtained from the linear fit of pK c versus √I/ (1 + 2.30√I) plot, contains the theoretical value of -2.04 predicted by the Debye-Hückel extended law. From the intercept, a value for the equilibrium dissociation constant of BCG, pK = (4.91 ± 0.02), is obtained, showing a reasonable agreement with literature data. The simplification makes it possible for students to complete the experiment in the course of an ordinary 3-h laboratory session. © 2012 The American Chemical Society and Division of Chemical Education, Inc.
author Rodríguez, Hernán Bernardo
Mirenda, Martín
spellingShingle Rodríguez, Hernán Bernardo
Mirenda, Martín
A simplified undergraduate laboratory experiment to evaluate the effect of the ionic strength on the equilibrium concentration quotient of the bromcresol green dye
author_facet Rodríguez, Hernán Bernardo
Mirenda, Martín
author_sort Rodríguez, Hernán Bernardo
title A simplified undergraduate laboratory experiment to evaluate the effect of the ionic strength on the equilibrium concentration quotient of the bromcresol green dye
title_short A simplified undergraduate laboratory experiment to evaluate the effect of the ionic strength on the equilibrium concentration quotient of the bromcresol green dye
title_full A simplified undergraduate laboratory experiment to evaluate the effect of the ionic strength on the equilibrium concentration quotient of the bromcresol green dye
title_fullStr A simplified undergraduate laboratory experiment to evaluate the effect of the ionic strength on the equilibrium concentration quotient of the bromcresol green dye
title_full_unstemmed A simplified undergraduate laboratory experiment to evaluate the effect of the ionic strength on the equilibrium concentration quotient of the bromcresol green dye
title_sort simplified undergraduate laboratory experiment to evaluate the effect of the ionic strength on the equilibrium concentration quotient of the bromcresol green dye
publishDate 2012
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00219584_v89_n9_p1201_Rodriguez
http://hdl.handle.net/20.500.12110/paper_00219584_v89_n9_p1201_Rodriguez
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