Titulações espectrofotométricas de sistemas ácido-base utilizando extrato de flores contendo antocianinas
Autor(a) principal: | |
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Data de Publicação: | 2007 |
Outros Autores: | , |
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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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 |
_version_ |
1750318106484408321 |