Titulações espectrofotométricas de sistemas ácido-base utilizando extrato de flores contendo antocianinas

Detalhes bibliográficos
Autor(a) principal: Cortes,Mônica Souza
Data de Publicação: 2007
Outros Autores: Ramos,Luiz Antônio, Cavalheiro,Éder Tadeu Gomes
Tipo de documento: Artigo
Idioma: por
Título da fonte: Química Nova (Online)
Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0100-40422007000400045
Resumo: Considering the attraction of the students' attention by the changes in the colors of vegetable crude extracts caused by the variation of the pH of the medium, the use of these different colors in order to demonstrate principles of spectrophotometric acid-base titrations using the crude extracts as indicators is proposed. The experimental setup consisted of a simple spectrophotometer, a homemade flow cell and a pump to propel the fluids along the system. Students should be stimulated to choose the best wavelength to monitor the changes in color during the titration. Since the pH of the equivalence point depends on the system titrated, the wavelength must be properly chosen to follow these changes, demonstrating the importance of the correct choice of the indicator. When compared with the potentiometric results, errors as low as 2% could be found using Rhododendron simsii (azalea) or Tibouchina granulosa (Glory tree, quaresmeira) as sources of the crude extracts.
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spelling Titulações espectrofotométricas de sistemas ácido-base utilizando extrato de flores contendo antocianinasacid-base chemistryinstrumental methodsspectrophotometric titrationsConsidering the attraction of the students' attention by the changes in the colors of vegetable crude extracts caused by the variation of the pH of the medium, the use of these different colors in order to demonstrate principles of spectrophotometric acid-base titrations using the crude extracts as indicators is proposed. The experimental setup consisted of a simple spectrophotometer, a homemade flow cell and a pump to propel the fluids along the system. Students should be stimulated to choose the best wavelength to monitor the changes in color during the titration. Since the pH of the equivalence point depends on the system titrated, the wavelength must be properly chosen to follow these changes, demonstrating the importance of the correct choice of the indicator. When compared with the potentiometric results, errors as low as 2% could be found using Rhododendron simsii (azalea) or Tibouchina granulosa (Glory tree, quaresmeira) as sources of the crude extracts.Sociedade Brasileira de Química2007-08-01info:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersiontext/htmlhttp://old.scielo.br/scielo.php?script=sci_arttext&pid=S0100-40422007000400045Química Nova v.30 n.4 2007reponame:Química Nova (Online)instname:Sociedade Brasileira de Química (SBQ)instacron:SBQ10.1590/S0100-40422007000400045info:eu-repo/semantics/openAccessCortes,Mônica SouzaRamos,Luiz AntônioCavalheiro,Éder Tadeu Gomespor2007-08-10T00:00:00Zoai:scielo:S0100-40422007000400045Revistahttps://www.scielo.br/j/qn/ONGhttps://old.scielo.br/oai/scielo-oai.phpquimicanova@sbq.org.br1678-70640100-4042opendoar:2007-08-10T00:00Química Nova (Online) - Sociedade Brasileira de Química (SBQ)false
dc.title.none.fl_str_mv Titulações espectrofotométricas de sistemas ácido-base utilizando extrato de flores contendo antocianinas
title Titulações espectrofotométricas de sistemas ácido-base utilizando extrato de flores contendo antocianinas
spellingShingle Titulações espectrofotométricas de sistemas ácido-base utilizando extrato de flores contendo antocianinas
Cortes,Mônica Souza
acid-base chemistry
instrumental methods
spectrophotometric titrations
title_short Titulações espectrofotométricas de sistemas ácido-base utilizando extrato de flores contendo antocianinas
title_full Titulações espectrofotométricas de sistemas ácido-base utilizando extrato de flores contendo antocianinas
title_fullStr Titulações espectrofotométricas de sistemas ácido-base utilizando extrato de flores contendo antocianinas
title_full_unstemmed Titulações espectrofotométricas de sistemas ácido-base utilizando extrato de flores contendo antocianinas
title_sort Titulações espectrofotométricas de sistemas ácido-base utilizando extrato de flores contendo antocianinas
author Cortes,Mônica Souza
author_facet Cortes,Mônica Souza
Ramos,Luiz Antônio
Cavalheiro,Éder Tadeu Gomes
author_role author
author2 Ramos,Luiz Antônio
Cavalheiro,Éder Tadeu Gomes
author2_role author
author
dc.contributor.author.fl_str_mv Cortes,Mônica Souza
Ramos,Luiz Antônio
Cavalheiro,Éder Tadeu Gomes
dc.subject.por.fl_str_mv acid-base chemistry
instrumental methods
spectrophotometric titrations
topic acid-base chemistry
instrumental methods
spectrophotometric titrations
description Considering the attraction of the students' attention by the changes in the colors of vegetable crude extracts caused by the variation of the pH of the medium, the use of these different colors in order to demonstrate principles of spectrophotometric acid-base titrations using the crude extracts as indicators is proposed. The experimental setup consisted of a simple spectrophotometer, a homemade flow cell and a pump to propel the fluids along the system. Students should be stimulated to choose the best wavelength to monitor the changes in color during the titration. Since the pH of the equivalence point depends on the system titrated, the wavelength must be properly chosen to follow these changes, demonstrating the importance of the correct choice of the indicator. When compared with the potentiometric results, errors as low as 2% could be found using Rhododendron simsii (azalea) or Tibouchina granulosa (Glory tree, quaresmeira) as sources of the crude extracts.
publishDate 2007
dc.date.none.fl_str_mv 2007-08-01
dc.type.driver.fl_str_mv info:eu-repo/semantics/article
dc.type.status.fl_str_mv info:eu-repo/semantics/publishedVersion
format article
status_str publishedVersion
dc.identifier.uri.fl_str_mv http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0100-40422007000400045
url http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0100-40422007000400045
dc.language.iso.fl_str_mv por
language por
dc.relation.none.fl_str_mv 10.1590/S0100-40422007000400045
dc.rights.driver.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv text/html
dc.publisher.none.fl_str_mv Sociedade Brasileira de Química
publisher.none.fl_str_mv Sociedade Brasileira de Química
dc.source.none.fl_str_mv Química Nova v.30 n.4 2007
reponame:Química Nova (Online)
instname:Sociedade Brasileira de Química (SBQ)
instacron:SBQ
instname_str Sociedade Brasileira de Química (SBQ)
instacron_str SBQ
institution SBQ
reponame_str Química Nova (Online)
collection Química Nova (Online)
repository.name.fl_str_mv Química Nova (Online) - Sociedade Brasileira de Química (SBQ)
repository.mail.fl_str_mv quimicanova@sbq.org.br
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