Navegando por Assunto "Química inorgânica"

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Determinação espectrofotométrica de cobalto com dioxima do ácido cromotrópico
(1979) Rodrigues, Rivaldo Alves
A coloração azul produzida pela reação de complexação do íon cobalto (11) com dioxima do ácido cromotrópico, em soluções amoniacais de cobalto, pode ser usada para a determinação seletiva de cobalto. Os melhores resultados foram obtidos quando se adicionou em balões aferidos para 50 ml aliquotas de solução 1 ,O7 x 10-M de Coc12. 6H20, 3,5 ml de solução 2,4 M deNH3, 10 ml de solução 1.41 x M de dioxima do ácido cromotrópico, água destilada para completar o volume e leituras espectrofotométricas de onda de 560 nm contra a solução amoniacal do reagente. O sistema obedece a Lei de Lambert-Beer num intervalo de concentração de 0,254 a 2,794 ug de coi2/ml. O erro relativo é aproximadamente 0,70% e o coeficiente de absortividade molar é em torno de 1,74 x 1 04. Interferem na proporção de 1:l I do ion coi2: 1 pg do ion interferente) Cu+² e Ni+²:10 Mg+². Cr+³, Mn+² Bi+³; 1:25 Ca+², Sr+², Cd+² e Pb+². 1:50 Ba+², Fe+², Zn+², Pd+² e Hg+² . Dentre os elementos estudados, o cobre e o níquel presentes são os que mais influenciam contudo, quando a razão foi reduzida para 1 :25, nenhuma influência foi observada com a determinação de cobalto na presença de solução 0,002 M de KCN.
Determinação espectrofotométrica do cobre pelo fenol vermelho + H²O²
(1979) Soares, Vera Maria; Rodrigues, Rivaldo Alves
O método fundamenta-se na reação de descoramento do fenol vermelho pelo H2O2 catalisada pelo íon Cu+2. As condições que mais favoreceram a reação foram em balões de 25 ml, adicionou se 1,25 ml do tampão KH2P04/Na0H pH = 6,0, 2,5 ml de H2O2 a 3%, 5,6 ml de fenol vermelho a 0,01%, alíquotas de solução de Cu+2, e água destilada para completar o volume, aquecimento a JQOC num banho termostático durante 20 minutos, resfriamento num banho de gelo por 5 minutos e leitura espectrofotométrica a 425 nm contra a água A lei de Lambert — Beer foi obedecida num intervalo de concentração de 0,4 x IO-2 a 2,8 x 10-2 ug de Cu+2 /ml, o erro relativo foi em tomo de 3,40% eo coeficiente de absortividade molar de 1,32x 10 mol.~ 11.cm-f Interferem na proporção de 1:1 Al+3; 1:10 Bi+². , Fe+². , Mn+². , Ce+4, Pt+4, Rh*3, Co+², Re+7, Ag+, 1:100 Hg+², Cr+3, Zn+² C204-2 c 1:1000 Pb+². Cd+². , Os+8, Pd+². , e Mo+b O método foi aplicado numa amostra de solo geoquímico que continha 53,24 ppm de Cu+², apresentando um desvio em tomo de 2,92%, em comparação com o método de absorção atômica.
Estudo espectrofotométrico do equilíbrio EBT - Complexos MY
(1979) Magalhães, Francisco de Oliveira
Na presença de EDTA (ácido etilenodiaminotetracético) a reação de complexação de íons metálicos com indicadores metalcrômicos não completa. A partir desta propriedade, propõe-se um método espectrofotométrico para a determinação da constante de equilibro de quelatos metálicos com indicadores metalcrômicos. usando as leituras de absorção de soluções que contenham concentrações constantes de agentes complexantes e do indicador e concentrações variáveis de íons metálicos.
Estudo sobre a influência das ligações [pi] na luminescência de novos complexos contendo íons lantanídeos
(2019-07-17) Cavalcante, Caroliny Oliveira; Belian, Mônica Freire; http://lattes.cnpq.br/2626644337183959; http://lattes.cnpq.br/2665095680217539
Researches about lanthanides ions have a growing interest in consequence of its photophysic properties, through several applications, among them; lasers, contrast agents, etc. These properties elapse from energy absorption of binder and emission in visible region because of metal type as example Eu3+ complexes which emit in red region. This process of energy transfer is called Antenna Effect. The carboxilate groups bond skillfully with these trivalent cations, for being Pearson’s hard bases and usually present high absorption and energy transfer. Some energy binder-metal transfer mechanisms are known, in which its study is necessary to creation of much more luminescence complexes, thus as spectroscopic studies and knowledge about binder’s triplet states, wherein such states are obtained from Gd3+ complexes’ phosphorescence. Because of that were synthetize complexes of trans-3(3-tienil)-acrylic acid and 4(2-tienil)-butyric acid with Eu3+ and Gd3+, mixing proportions; 3:1 and 4:1. The acids, carboxilates and all complexes were characterized by Infrared Spectroscopy, and done a spectroscopic study through Eletronic Luminescense Spectroscopy. In which were noticed the symmetric and asymmetric bands of group OCO-, besides maximum of excitation and emission of each Eu3+ complex. The emissions intensity on 5D0 -7F2 hypersensible transitions from ion were higher in Eu-ATA-3:1 and Eu-ATB-4:1, with diference between state T1 of binder and state D2 of ion near 440 cm-1 e 550 cm-1, respectively.
Síntese do pigmento CoCr2O4 pelo método de gelatina comercial
(2018) Sousa, Tassia Pereira de; Câmara, Maria Suely Costa da; http://lattes.cnpq.br/9163311260887432; http://lattes.cnpq.br/7879045291487919
There is a growing interest of the ceramic industries in developing more stable pigments that are low cost and little environmental damage. The ceramic industries mainly use pigments of predominantly inorganic nature, such pigments are the most used because they havean excellent chemical and thermal stability besides a lower toxicity to the man and few environmental damages. The most commonly used inorganic pigments used in ceramics are mixed oxides with spinel structure and AB2O4. Spinels are one of the most interesting crystalline structures in the development of stable and chemically inert pigments. In this structure, ions of different oxidation states are present in both tetrahedral and octahedral sites. In addition, there are several ways of arranging the cationsat these sites (normal and inverse spinel). These characteristics led to the development of different colors, being these intense and stable, suitable for use as pigments. Among the compounds used as ceramic pigments, we have highlighted CoCr2O4which is a mineral oxide belonging to the group of spinel, such structures cover a group of well-establishedmagnetic materials that may have a green coloration. The objective of the present work was to synthesize the CoCr2O4pigment using commercial gelatin as precursor and to characterize the following techniques: Thermogravimetric analysis (TG), Xray diffraction (XRD), surface area (BET), Scanning electron microscopy (SEM) spectroscopy in the infrared region (FTIR), and colorimetric measurements by the CIEL*a*b*method. The route of synthesis used was confirmed viable from the results. Crystalline, monophasic and high surface area compounds were obtained. The powders presented green coloration with phase obtained from 500 ºC.
Síntese e caracterização de novos compostos de coordenação de oxidovanádio (IV) contendo ligantes podantes
(2021-07-15) Silva Neto, José Paulino da; Belian, Mônica Freire; Silva, Wagner Eduardo da; http://lattes.cnpq.br/8612340815622413; http://lattes.cnpq.br/2626644337183959; http://lattes.cnpq.br/3123733088755951
Since the 70’, inorganic compounds have been studied and applied as alternatives in the treatment of several diseases such as cancers, rheumatoid arthritis, and diabetes mellitus (DM). The latter is a disease that, due to its high incidence, has worrying epidemiological numbers. DM can be caused by genetic or external factors and causes serious disturbances in the metabolism of proteins, carbohydrates, and lipids, and can be classified into two subtypes. Type 1 (DM1) is caused by the non-secretion of insulin due to the autoimmune destruction of pancreatic β-cells; type 2 (DM2) occurs when cells in peripheral tissues become resistant to the chemical stimulation of the insulin. In both cases, the patients have the general picture of high blood glucose (hyperglycemia). to improve or provide alternatives to the current treatments against diabetes, compounds based on metals such as vanadium have been studied and developed, due to their already recognized antidiabetic activity. Thus, in this work, vanadium compounds were synthesized using organic ligands to providing greater absorption and fewer side effects in future applications of the compounds obtained. Furthermore, the synthesized compounds were also characterized, as well as the ligands, which underwent chemical modifications. And based on the results of spectroscopy in the infrared region, as the displacements, the lower wavenumber of the sulfone group of taurine, or the intense peak referring to the stretching of the C=O bond (1668 cm-1) in the ligand T2DO (in addition to NMR data of 1H and 13C, for this ligand) corroborate with the proposed structures and with the operation of the methodologies used. The mass spectra show strong evidence for obtaining oxovanadium complexes (IV) with the suggested structures since besides being possible to verify the peak referring to the molecular ion it is also possible to predict fragmentations in the structures of the chemical species.
Uso de modelos na abordagem de geometria de sólidos cristalinos: experiência vivenciada na monitoria de Química Inorgânica L1
(2021-07-12) Aciole, Rayane Cristine Gomes; Barros, Ivoneide de Carvalho Lopes; http://lattes.cnpq.br/5272867419216787; http://lattes.cnpq.br/2384434357313163
The objective of this work is to study crystalline solid structures using low-cost molecular models from a sequential didactic intervention. This research was executed out during the academic monitoring period in order to improve the understanding of students about inorganic chemistry subject in the chemistry course. This work followed a pretest-posttest design on chemical bonds and solid structures, before and after the didactic intervention. The participants were 19 undergraduate students from a 4th period college chemistry course. The results obtained previously indicated that the students' understanding of chemical bonds was regular. Regarding questions about solid 90% of the students' answers were categorized as unsatisfactory. In the didactic intervention, the concrete models was built with Styrofoam balls and wooden sticks by the students. Then, non-tradicional classes and oral activities were applied. With the results of the post-test it was observed the students were able to use and visualize the built models as a tool to learn concepts of crystalline solids. At the end of the process, all students evaluated the methodology used as positive. Therefore, this study showed that the use of concrete models is an effective strategy for teaching solid structures. Finally, this research indicated that it is necessary to devote more time to teach the concept about chemical bonds within this theme and also others in Chemistry for a better understanding of this content.