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4 results on '"ACTIVITY coefficients"'

1. Determinação do coeficiente de atividade na diluição infinita em sistemas etanol-água-sal por microextração em fase sólida-gc-fid

Author

Andrew Milli Elias, Filipe Arantes Furtado, and Gerson Luiz Vieira Coelho

Subjects
solid-phase microextraction (SPME), activity coefficients, salt effect, gas chromatography, phase equilibrium, Chemistry, QD1-999
Abstract

A new method using the headspace solid phase microextraction (HS-SPME) technique was used to evaluate the infinite dilute activity coefficient (γ1∞) in an alcohol/water/salt system. The studied systems were ethanol and water with NaCl and NH4Cl at salt concentrations of 5, 10, 15, and 30% m/v and temperatures of 303.15 and 313.15 K. The method was used to investigate the salt effect on vapor/liquid equilibrium in an ethanol/water system, yielding satisfactory results. The study focused on the rich side in ethanol. The data were compared with the literature infinite dilution data determined by other methods such as differential ebulliometry (EBUL), differential static cell equilibrium (STAT), and gas-liquid chromatography with no gas phase correction (GC). In this study, NaCl showed better separation rates than NH4Cl.

Published
2014
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2. Determinação do coeficiente de atividade em diluição infinita de hidrocarbonetos em furfural a 298,15 K por SPME-GC/FID

Author

Filipe Arantes Furtado and Gerson Luiz Vieira Coelho

Subjects
partition coefficients, activity coefficients, gas chromatography, Chemistry, QD1-999
Abstract

In this work a new method (SPME-GC/FID) was developed to analyze the activity of binary liquid mixtures. The purpose is to demonstrate that SPME is capable to be used to determinate activity coefficients at infinite dilution knowing the fiber properties, with a lower cost than the conventional methods encountered in literature such as GLC. The activity coefficients at infinite dilution in furfural for n-hexane, n-heptane and cyclohexane at 298.15 K was determined using SPME and deviations of literature data was about 7%.

Published
2010
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3. VALORES NUCLEARES APLICADOS À EDUCAÇÃO TECNOLÓGICA COLABORATIVA.

Author

Amboni Stadtlober, Maria Goreti

Subjects
*EDUCATION, *TECHNOLOGY, *ANTIQUITIES, *ACTIVITY coefficients, *METHODOLOGY
Abstract

This study concerns pedagogic action with socioeductional and technological focus that interprets knowledge as an interdisciplinary, interactive and situated issue. This reflection influences the particularity of the pedagogic process associated with educational technology, thus broadening vision and not stcking to any particular methodology. However, it is proposed that when the methods are used, they should be chosen according to the problems to be solved. Technology is then conceived as a mediating artifact of human activities, but it should never occupy an ontological space (referring to the being). It reflects on the need of new definitions for education oulined by nuclear social values and interdependent pedagogic axes that contribute to the development of community network. [ABSTRACT FROM AUTHOR]

Published
2008

4. Determinação de parâmetros físico-químicos com um sensor potenciométrico sensível ao íon p-aminobenzoato

Author

Leonardo Pezza, A. O. Santini, Helena Redigolo Pezza, E. S. da Silva Júnior, Universidade Estadual Paulista (UNESP), and Universidade Estadual Paulista (Unesp)

Subjects
Activity coefficient, Molality, Aqueous solution, Activity coefficients, Analytical chemistry, Potentiometric sensor, General Physics and Astronomy, chemistry.chemical_element, Ionic bonding, General Chemistry, Thermodynamic solubility-product constant, constante termodinâmica do produto de solubilidade, Mercury (element), Ion, Metal, p-aminobenzoato, chemistry, visual_art, Electrode, visual_art.visual_art_medium, coeficiente de atividade individual iônico, P-aminobenzoate, sensor potenciométrico
Abstract

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:49:13Z No. of bitstreams: 1 S0100-46702004000100002.pdf: 150206 bytes, checksum: 2e933ee5bace4e64a8cc8a2f164e0099 (MD5) Made available in DSpace on 2013-08-22T18:49:13Z (GMT). No. of bitstreams: 1 S0100-46702004000100002.pdf: 150206 bytes, checksum: 2e933ee5bace4e64a8cc8a2f164e0099 (MD5) Previous issue date: 2004-01-01 Made available in DSpace on 2013-09-30T19:39:28Z (GMT). No. of bitstreams: 2 S0100-46702004000100002.pdf: 150206 bytes, checksum: 2e933ee5bace4e64a8cc8a2f164e0099 (MD5) S0100-46702004000100002.pdf.txt: 30736 bytes, checksum: 87364493d755f52848b5e811ebc2853d (MD5) Previous issue date: 2004-01-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T14:21:02Z No. of bitstreams: 2 S0100-46702004000100002.pdf: 150206 bytes, checksum: 2e933ee5bace4e64a8cc8a2f164e0099 (MD5) S0100-46702004000100002.pdf.txt: 30736 bytes, checksum: 87364493d755f52848b5e811ebc2853d (MD5) Made available in DSpace on 2014-05-20T14:21:02Z (GMT). No. of bitstreams: 2 S0100-46702004000100002.pdf: 150206 bytes, checksum: 2e933ee5bace4e64a8cc8a2f164e0099 (MD5) S0100-46702004000100002.pdf.txt: 30736 bytes, checksum: 87364493d755f52848b5e811ebc2853d (MD5) Previous issue date: 2004-01-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação para o Desenvolvimento da UNESP (FUNDUNESP) Este trabalho descreve a construção e a determinação de parâmetros físico-químicos com um eletrodo de segunda ordem do tipo, Pt|Hg|Hg2(PAB)2|Grafite, sensível ao íon p-aminobenzoato (PAB). O eletrodo é construído facilmente, apresenta um rápido tempo de resposta, é de baixo custo e tem um tempo de vida útil superior a 12 meses. Utilizando o referido eletrodo foi possível estimar os coeficientes de atividade iônica individuais do PAB, a 25ºC, em força iônica ajustada entre 0,700-3,000 mol L-1 com NaClO4, em solução aquosa. O potencial molal padrão do eletrodo determinado a 25ºC é de (445,5 ± 0,5) mV. A constante termodinâmica do produto de solubilidade, T Kps (I=0) do Hg2(PAB)2 determinada com o eletrodo é de (T Kps = 2,50 x 10-12 mol³ L-3 , a 25ºC). Uma característica favorável consiste no fato de que o eletrodo pode ser utilizado para determinar a concentração de íons p-aminobenzoato livres em sistemas complexos de íons metálicos. The paper describes the construction and determination of physical chemical parameters with a second kind electrode, Pt|Hg|Hg2(PABA)| Grafite, sensitive to p-aminobenzoate ion (PAB). Electrode construction is easy, presents a fast response time (30 sec), low-cost, excellent response stability and (lifetime > 12 months, under continuous use). Using of the mercury(I) p-aminobenzoate electrode, the molar single activity coefficient associated with PAB (yPAB) was estimated at 25ºC and ionic strengths between 0.700-3.000 mol L-1 (NaClO4). The standard molal potential of the electrode at 25ºC is 445.5 ± 0.5 mV. The thermodynamic solubility-product constant of mercurous p-aminobenzoate determined with the mentionated electrode , in aqueous solution, at 25ºC was T Kps = 2.50 x 10-12 mol³ L-3 . An important feature of the electrode is that it permits the determination of the concentration of free p-aminobenzoate ions in complex systems of metallic ions. Universidade Estadual Paulista Instituto de Química Universidade Estadual Paulista Instituto de Química

Published
2004

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