scholarly journals Evaluation of Stoichiometry, Stability Constants and Gibbs Free Energies of Acetaminophen-Zn (II) complex at Different Temperatures

2020 ◽  
Vol 24 (7) ◽  
pp. 1137-1143
Author(s):  
O.V. Ikpeazu ◽  
I.E. Otuokere ◽  
K.K. Igwe
Keyword(s):  
Free Energy ◽  
Stability Constant ◽  
Gibbs Free Energy ◽  
Stability Constants ◽  
Continuous Variation ◽  
Variation Method ◽  
Ratio Method ◽  
Free Energies ◽  
Different Temperatures ◽  
Continuous Variation Method

Acetaminophen also known as paracetamol, is a drug used in the treatment of pain and fever. It is essentially used for the relief of mild to moderate pain. The presence of phenol and carbonyl oxygen atom enables acetaminophen to behave as a bidentate ligand. The stoichiometry, stability constants and Gibbs free energies of acetaminophen-Zn (II) were determined colorimetrically at 25 and 40 oC using continuous variation and mole  ratio methods. The formation of Zn (II) complex with acetaminophen was studied colorimetrically at an absorption maximum of 630 nm at different temperatures. The data showed that Zn (II) and acetaminophen combine in the molar ratio of 1:1 at pH 7.4 with ionic strength maintained using 0.1M KNO3. Calculated stability constants values were 2.70 x 103 and 2.20 x 103 using continuous variation method and 7.21 x 103 and 7.21 x 103 using mole ratio methods at 25 and 40 oC respectively. Calculated ΔGƟ for the complex were - 1.96 x 104 and -1.98 x 104 J using continuous variation method and -2.2 x 104 J and - 2.31 x 104 J using mole ratio method at 25 and 40 oC respectively. The stability constant and Gibbs free energy results suggested that acetaminophen used in the study is a good chelating agent and can be an efficient antidote in the therapy of Zn (II) overload or poisoning. Keywords: Acetaminophen, Zinc, complex, stability constant, Gibbs free energy.

scholarly journals Determination of Stability Constants and Thermodynamic parameters of Cefotaxime –Fe(III) Complex at Different Temperatures

2020 ◽  
Vol 45 (4) ◽  
Author(s):  
O. V. Ikpeazu ◽  
I. E. Otuokere ◽  
K. K. Igwe
Keyword(s):  
Stability Constants ◽  
Chelating Agent ◽  
Continuous Variation ◽  
Molar Ratio ◽  
Variation Method ◽  
Ratio Method ◽  
Lactam Antibiotic ◽  
Different Temperatures ◽  
Mole Ratio Method ◽  
Continuous Variation Method

Cefotaxime, a β-lactam antibiotic, has a structure which enables it to act as a chelating agent. The formation of Fe(III) complex with cefotaxime has been studied colorimetrically at an absorption maximum of 480 nm at different temperatures. The data showed that Fe(III) and cefotaxime combine in the molar ratio of 1:1  at pH 7.4 with ionic strength maintained using 0.1M KNO3. The stability constants of the complex were calculated to be 1.56 - 1.90 x 104 by continuous variation method and 1.34 - 1.71 x 104 by mole ratio method at 25 and 40 oC respectively. ∆HƟ values for the complex were calculated to be -1.02 x 104 and -1.05 x 104 J by continuous variation method and mole ratio method respectively. ∆GƟ of the complex were calculated to be -2.44 – (-2.51) x 104 J by continuous variation method and -2.41- (- 2.48)  x 104 J by mole ratio method at 25 and 40 oC.  ∆SƟ of the complex were calculated to be 2.44 - 2.51 x 104 J/K by continuous variation method and -2.41 -2.48) x 104 J/K by mole ratio method at 25 and 40 oC respectively. Cefotaxime is a good chelating agent and can be an efficient antidote in the therapy of copper overload or poisoning.  

scholarly journals Colorimetric Determination of Stability Constant of Sulfamethoxazole-Cu(II) Complex at Different Temperatures by Continuous Variation Method

2020 ◽  
Vol 5 (7) ◽  
pp. 78-83
Author(s):  
O.V. Ikpeazu ◽  
I.E. Otuokere ◽  
K.K. Igwe
Keyword(s):  
Stability Constant ◽  
Bacterial Infections ◽  
Classical Equation ◽  
Theoretical Explanation ◽  
Continuous Variation ◽  
Molar Ratio ◽  
Variation Method ◽  
Colorimetric Determination ◽  
Continuous Variation Method ◽  
Tract Infections

Sulfamethoxazole is an antibiotic that is used for the treatment of bacterial infections such as prostatitis, bronchitis and urinary tract infections. It is effective against gram negative and gram positive bacteria. Classical equation has been used in the calculation of stability constant of SulfamethoxazoleCu(II) complex depending on the theoretical explanation of the stoichiometry. The formation of Cu(II) complex with sulfamethoxazole was studied colorimetrically at an absorption maximum of 430 nm at 25, 30, 35 and 40 oC. The data showed that Cu(II) and sulfamethoxazole combine in the molar ratio of 1:2 at pH 7.4 with ionic strength maintained using 0.1M KNO3. Calculated stability constants values were 4.02 x 106 , 2.93 x 106 , 1.37 x 106 and 9.21 x 105 using continuous variation method. Calculated ∆GƟ for the complex were -3.77 x 104 , -3.75 x 104 , -3.62 x 104 and - 3.57 x 104 . The stoichiometry, stability constant and Gibbs free energy results suggested that sulfamethoxazole used in the study is a good chelating agent and can be an efficient antidote in the therapy of Cu(II) overload or poisoning

Chelate formation between lead(II) and 1,2,5,8-tetrahydroxyanthraquinone (quinalizarin): Spectrophotometric studies on the composition and stability

1967 ◽  
Vol 20 (7) ◽  
pp. 1385 ◽  
Author(s):  
KC Srivastava ◽  
SK Banerji
Keyword(s):  
Free Energy ◽  
Aqueous Ethanol ◽  
Free Energy Change ◽  
Energy Change ◽  
Variation Method ◽  
Ratio Method ◽  
Chelate Formation ◽  
Mole Ratio Method ◽  
Continuous Variation Method ◽  
Absorbance Data

The formation of a bluish violet chelate between bivalent lead and 1,2,5,8-tetrahydroxyanthraquinone (quinalizarin) with maximum absorption at 520mμ has been studied. The chelate is soluble in aqueous ethanol. The composition of the chelate has been determined by three methods. The chelate has a composition of 1 : 1 and is stable at pH 6.1-8.5. The values of log K determined in 50% ethanolic medium by the method of Dey et al., the continuous variation method, and the mole ratio method, using absorbance data, are 4.1 � 0.1, 4.0 � 0.0, and 4.1� � 0.1 respectively at 30�, pH 6.3. The free energy change of formation, calculated from the three values of log K, is -5.7 � 0.1, -5.6 � 0.0, and -5.7 � 0.1 kcal respectively.

Chemical equilibrium and chemical kinetics

2018 ◽  
Author(s):  
Dennis Sherwood ◽  
Paul Dalby
Keyword(s):  
Free Energy ◽  
Equilibrium Constant ◽  
Gibbs Free Energy ◽  
Chemical Kinetics ◽  
Chemical Equilibrium ◽  
First Principles ◽  
Effect Of Temperature ◽  
Total System ◽  
Free Energies

Building on the previous chapter, this chapter examines gas phase chemical equilibrium, and the equilibrium constant. This chapter takes a rigorous, yet very clear, ‘first principles’ approach, expressing the total Gibbs free energy of a reaction mixture at any time as the sum of the instantaneous Gibbs free energies of each component, as expressed in terms of the extent-of-reaction. The equilibrium reaction mixture is then defined as the point at which the total system Gibbs free energy is a minimum, from which concepts such as the equilibrium constant emerge. The chapter also explores the temperature dependence of equilibrium, this being one example of Le Chatelier’s principle. Finally, the chapter links thermodynamics to chemical kinetics by showing how the equilibrium constant is the ratio of the forward and backward rate constants. We also introduce the Arrhenius equation, closing with a discussion of the overall effect of temperature on chemical equilibrium.

scholarly journals Kinetics and thermodynamic properties related to the drying of 'Cabacinha' pepper fruits

2016 ◽  
Vol 20 (2) ◽  
pp. 174-180 ◽  
Author(s):  
Hellismar W. da Silva ◽  
Renato S. Rodovalho ◽  
Marya F. Velasco ◽  
Camila F. Silva ◽  
Luís S. R. Vale
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Free Energy ◽  
Thermodynamic Properties ◽  
Gibbs Free Energy ◽  
Removal Rate ◽  
Effective Diffusion ◽  
Drying Time ◽  
Three Samples ◽  
Different Temperatures

ABSTRACT The objective of this study was to determine and model the drying kinetics of 'Cabacinha' pepper fruits at different temperatures of the drying air, as well as obtain the thermodynamic properties involved in the drying process of the product. Drying was carried out under controlled conductions of temperature (60, 70, 80, 90 and 100 °C) using three samples of 130 g of fruit, which were weighed periodically until constant mass. The experimental data were adjusted to different mathematical models often used in the representation of fruit drying. Effective diffusion coefficients, calculated from the mathematical model of liquid diffusion, were used to obtain activation energy, enthalpy, entropy and Gibbs free energy. The Midilli model showed the best fit to the experimental data of drying of 'Cabacinha' pepper fruits. The increase in drying temperature promoted an increase in water removal rate, effective diffusion coefficient and Gibbs free energy, besides a reduction in fruit drying time and in the values of entropy and enthalpy. The activation energy for the drying of pepper fruits was 36.09 kJ mol-1.

scholarly journals Rationalisation of the activities of phenolic (vitamin E-type) antioxidants

2003 ◽  
Vol 17 (4) ◽  
pp. 753-762
Author(s):  
Christopher J. Rhodes ◽  
Thuy T. Tran ◽  
Philip Denton ◽  
Harry Morris
Keyword(s):  
Free Energy ◽  
Vitamin E ◽  
Gibbs Free Energy ◽  
State Theory ◽  
Linear Free Energy Relationship ◽  
Free Energies ◽  
Gibbs Free Energy Change ◽  
Linear Free Energy ◽  
Free Energy Of Activation ◽  
Enthalpy And Entropy

Using Transition-State Theory, experimental rate constants, determined over a range of temperatures, for reactions of vitamin E type antioxidants are analysed in terms of their enthalpies and entropies of activation. It is further shown that computational methods may be employed to calculate enthalpies and entropies, and hence Gibbs Free Energies, for the overall reactions. Within the Linear Free Energy Relationship (LFER) assumption, that the Gibbs Free Energy of activation is proportional to the overall Gibbs Free Energy change for the reaction, it is possible to rationalise, and even to predict, the relative contributions of enthalpy and entropy for reactions of interest, involving potential antioxidants.

Modeling of Liquid-Liquid Demixing Curve in Lead-Zinc Binary System

2018 ◽  
Vol 18 ◽  
pp. 49-54
Author(s):  
Naceur Amel ◽  
Adjadj Fouzia
Keyword(s):  
Mathematical Model ◽  
Free Energy ◽  
Phase Separation ◽  
Binary System ◽  
Free Energies ◽  
Common Tangent ◽  
Different Temperatures ◽  
Lead Zinc ◽  
The Common ◽  
Zn Alloys

In this work we discussed the modeling of the demixing curve in the liquid state in the Lead – Zinc binary system. We are interested to recalculate the free energies relating on Pb-Zn alloys for several temperatures based on the thermodynamic data collected in the bibliography. This calculation allows us to trace the curve of phase separation from a program after obtaining the mole fractions corresponding to the common tangent to the curve of the free energy with two minima at different temperatures. To do this, we used the Matlab 7.1 as the programming language and the Redlich-Kister polynomial as a mathematical model of development. The results obtained are very satisfactory by comparing them with those of the bibliography.

scholarly journals Determination of Iron in Raw Materials, During Fabric Processing, and in Wastewaters of the Textile Industry

1999 ◽  
Vol 82 (3) ◽  
pp. 683-688 ◽  
Author(s):  
Zorana Grabaric ◽  
Ljerka Bokic ◽  
Branka Stefanovic
Keyword(s):  
Stability Constants ◽  
Textile Industry ◽  
Raw Materials ◽  
Variation Method ◽  
Ratio Method ◽  
Industrial Water ◽  
Complex Species ◽  
Woolen Fabric ◽  
Good Agreement

Abstract The Schiff base 2-(2-pyridylmethyieneamino)phenol (PMAP) was investigated as a spectrophotometric reagent for determination of iron in caustic soda, cotton yarn and fabric, woolen fabric, and industrial water. The solution properties of Fe(III)-PMAP complexes were determined. At pH 4.4 and 5.6, Fe(III) forms stable complexes with PMAP, with molar absorption coefficients (ε) of 3.00 × 103 and 7.44 × 103/M.cm, respectively. Composition and cumulative stability constants were determined by the mole ratio method (MRM) and the mole fraction variation method (MFVM). At the lower pH (4.4), the predominant complex species in the solution obtained with both methods are ML2, with fairly good agreement of stability constants: log βML2 = 7.00 ± 0.04 with MRM and 7.31 ± 0.01 with MFVM. At the higher pH (5.6), the composition and stability constants of predominant complex species in the solution obtained with the 2 methods were not in good agreement, perhaps because of the coexistence of several species, such as Fe-PMAP, Fe-hydroxo, and Fe-acetate complexes. PMAP is a sensitive reagent for determination of Fe(III). The detection limit of 0.4 μg/mL is lower than those of other frequently used spectrophotometric reagents for Fe. The reagent is ecologically more acceptable, because extraction with organic solvents is avoided. All measurements were made at pH 5.6 because sensitivity was higher at this pH. The high Fe values obtained for industrial water (31.8 μg/mL) indicate that some modifications in the process have to be done. Concentration of Fe in wastewater was much lower (15.9 μg/mL). The results for cotton and woolen fabric indicate that accumulation of Fe in wool is much higher than in cotton (84.4 μg/mL and 29.3-53.1 μg/mL, respectively).

Design and Thermodynamic Analysis on One-Step Amination of Benzene to Aniline Systems

2012 ◽  
Vol 550-553 ◽  
pp. 2607-2611
Author(s):  
Chun Hua Yang ◽  
Gang Chen ◽  
Long Zhang
Keyword(s):  
Hydrogen Peroxide ◽  
Free Energy ◽  
Equilibrium Constant ◽  
Gibbs Free Energy ◽  
Driving Force ◽  
Theoretical Basis ◽  
Free Energies ◽  
One Step ◽  
The One ◽  
Further Development

Seven systems of one-step synthesis of aniline were designed, and it was determined which one could occur spontaneously through the calculation of Gibbs free energy of it. Among the seven systems, the Gibbs free energy of the one with ammonia as the aminating agent and hydrogen peroxide as the oxidant was the lowest, thus its process driving force was the largest, that is, .For this system just mentioned above, the standard Gibbs free energies, the equilibrium constant and the equilibrium conversions of benzene under different conditions were discussed ,which was expected to provide a theoretical basis for further development and application of the system.

Effect of mechanical activation on the structure of pulverized coal and iron ore powder

2019 ◽  
Vol 116 (6) ◽  
pp. 624
Author(s):  
Rufei Wei ◽  
Dongwen Xiang ◽  
Hongming Long ◽  
Jiaxin Li ◽  
Qingmin Meng
Keyword(s):  
Free Energy ◽  
Mechanical Activation ◽  
Gibbs Free Energy ◽  
Iron Ore ◽  
Pulverized Coal ◽  
Activation Process ◽  
Free Energies ◽  
Boundary Area ◽  
Particle Sizer ◽  
Storage Energy

Morphologies and structures of pulverized coal and iron ore powder after mechanical activation were studied by SEM, XRD, FTIR and laser particle sizer. The microcrystalline structure of coal was found to be destroyed by mechanical activation via reducing the pile height and number of layers, and the organic structure of coal was altered through the destruction of the ether bond. Mechanical activation led to distortions and dislocations of the crystal lattice of iron ore, decreasing crystallite size, increasing the grain boundary area, and producing an amorphous phase. These increased the Gibbs free energies of dislocations and grain boundaries as well as the surface Gibbs free energy and the amorphization Gibbs free energy, which would eventually increase the energy stored in iron ore called mechanical storage energy. The longer the mechanical activation process, the higher mechanical storage energy for the iron ore will be saved. The amorphization Gibbs free energy is the biggest among the four kinds of Gibbs free energy, accounting for 94.8% ∼ 87.1% of the total storage energy in the mechanical activated iron ore.

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