Determination of Kinetic Parameters of the Crystal Violet Reaction With Sodium Hydroxide Applying Absorbance Technique and the Laws of Lambeert-Beer and Arrhenius

Abstract

A reaction widely used to test CSTR reactors is the reaction between crystal violet and sodium hydroxide, since crystal violet discolouration occurs in proportion to the reaction's progress (ATKINS, 2006;RANGEL, 1995). The present work has the objective of verifying first order kinetics and obtaining the kinetic parameters, such as rate constant, frequency factor and activation energy for the present reaction. A calibration curve was constructed, obeying the Lambeert-Beer Law, so that it is possible to know the concentration in each time period of the reaction by the absorbance technique. All samples were analyzed at a wavelength of 595nm, due to providing a higher absorbance value. The results obtained were proportionality constant of 824,383 L mol DETERMINAÇÃO DE PARÂMETROS CINÉTICOS DA REAÇÃO DO CRISTAL VIOLETA COM O HIDRÓXIDO DE SÓDIO APLICANDO A TÉCNICA DA ABSORBÂNCIA E AS LEIS DE LAMBEERT-BEER E ARRHENIUSRESUMO Uma reação bastante utilizada a fim de testes em reatores do tipo CSTR é a reação entre cristal violeta e hidróxido de sódio, já que ocorre a descoloração do cristal violeta em proporção ao avanço da reação (ATKINS, 2006;RANGEL, 1995). O presente trabalho tem como objetivo a verificação da cinética de primeira ordem e obtenção dos parâmetros cinéticos, como a constante de velocidade, o fator de frequência e a energia de ativação para a presente reação. Construiu-se uma curva de calibração, obedecendo a Lei de Lambeert-Beer, para que seja possível saber a concentração em cada período de tempo da reação por meio da técnica da absorbância. Todas as amostras foram analisadas a um comprimento de onda de 595nm, devido a fornecer um maior valor de absorbância. Os resultados obtidos foram: constante de proporcionalidade de 824.383 L mol -1 cm -1

Liquid–liquid phase reaction between crystal violet and sodium hydroxide: kinetic study and precipitate analysis

“…As shown in figure 3 b–e , all datasets are linear when the natural log of [CV + ] is plotted against reaction time, indicating that the order dependence with respect to [CV + ] is 1st order, which is in accordance with previous studies [ 4 , 12 , 13 , 18 ].

Figure 3 ( a ) Calibration plot for UV-vis absorbance versus CV concentration.

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“…(M) NaOH conc. (M) 6°C 2.600 × 10 −6 0.008–0.024 0.032 [s −1 ] 0.38 0.62 [ 4 ] 21°C 2.600 × 10 −6 0.008–0.024 0.120 [s −1 ] 0.24 0.76 [ 4 ] 30°C 8.812 × 10 −5 0.04 0.130 [M −1 s −1 ] 1.00 1.00 [ 13 ] 7.5°C 1.985 × 10 −5 0.01–0.05 0.034 [M −1 s −1 ] 1.00 1.00 [ 14 ] 21°C 1.985 × 10 −5 0.01–0.05 0.118 [M −1 s −1 ] 1.00 1.00 [ 14 ] 45°C 1.985 × 10 −5 0.01–0.05 0.721 [M −1 s −1 ] 1.00 1.00 [ 14 ] room temp. a 1.0 × 10 −5 0.004–0.008 0.160 [M −1 s −1 ] 1.00 1.00 [ …”

“…Another variation in the rate constants may arise due to the selection of different CV peak wavelengths (i.e. 530, 590 and 595 nm) from the UV-vis spectra, although this effect is expected to be minor [ 13 , 14 ]. As shown in table 1 , it is clear that the reaction rate is directly related to the reaction temperature.…”

“…Highly concentrated solutions of NaOH may lead to a difference in the reaction rate constant, which requires further investigation. Based on the literature results, it is concluded that several reaction conditions such as mixing conditions, concentrations of reactants (CV or NaOH) and reaction temperatures, could contribute to the discrepancy of rate constants [4,[13][14][15][16]. The steady state or transient state condition may also affect the rate constant values.…”

Studi Stabilitas Kadar Parasetamol Drops yang Dicampur Minuman Teh Manis Pada Suhu Ruang (≤ 30 °C) Dan Suhu Dingin (2-8 °C)

“…Hal ini dapat dilakukan dengan cara membuat kurva kalibrasi dari beberapa set larutan standar yang telah diketahui konsentrasinya 18 . Kurva kalibrasi merupakan metode standar yang dapat digunakan untuk menentukan konsentrasi suatu analit berdasarkan hukum Lambert-Beer 19 . Hasil absorbansi pada uji linearitas atau kurva baku terdapat pada gambar 2.…”