scholarly journals EQUILIBRIA PROCESSES IN AQUEOUS SOLUTIONS OF K2CrO4 – HNO3 – KNO3 – H2O AND K2Cr2O7 – NaOH – KNO3 – H2O SYSTEMS

2021 ◽  
Vol 26 (2(78)) ◽  
pp. 56-72
Author(s):  
Yu. A Oleksii ◽  
O. Yu. Mariichak ◽  
G. M. Rozantsev ◽  
S. A. Shyshkanov ◽  
S.V. Radio
Keyword(s):  
Mathematical Modeling ◽  
Aqueous Solutions ◽  
Equilibrium Constants ◽  
Equilibrium Concentration ◽  
Quantitative Composition ◽  
Anion Formation ◽  
Chromium Vi ◽  
Vis Spectroscopy ◽  
Pitzer Method ◽  
Quasi Newton

The equilibria processes in aqueous solutions of CrO42– – H+ – H2O and Cr2O72– – OH– – H2O systems were studied by pH‑potentiometric titration, mathematical modeling and UV–Vis. spectroscopy. It was established that in the CrO42– – H+ – H2O systems with acidity ZН = ν(H+)/ν(Cr(VI)) = 0–2.5 the processes of dichromate and hydrochromate anion formation and hydrolytic conversion of dichromate to hydrochromate take place, for which the logarithms of the equilibrium concentration constants were calculated by the quasi-Newton method (CLINP 2.1 software; 95 % confidence probability). The calculated values of the logarithms of the concentration equilibrium constants lgKC reliably agree with the literature data. The calculated lgKC were used to build of chromium(VI) anions distribution diagrams depending on ZH, and ZOH in solutions. For the first time, by the Pitzer method the thermodynamic equilibria constants of hydrochromate HCrO4– (lgK10 = 6,94), the dichromate anion Cr2O72– (lgK20 = 15,49) formation processes from the CrO4 2– and H+ ions, and the logarithm of equilibrium constant of the interconversion of the dichromate anion to the hydrochromate anion (lgK30 = –1,61) were calculated. Mathematical modeling and UV–Vis. spectroscopy show that the composition of anions in Cr2O72– – OH– – H2O solutions with alkality ZOH = ν(OH–)/ν(Cr(VI)) = 0–2.5 is identical to CrO42– – H+ – H2O systems. It is established that the experimental dependencies pH = f(Z) for the Cr2O72– – OH– – H2O system can be reliably reproduced by hydrolysis reactions of dichromate anion to hydrochromate anion and by subsequent neutralization to chromate anion with equilibrium constants calculated for processes in CrO42– – H+ – H2O solutions with same ionic strengths. The quantitative composition of chromium(VI) solutions was confirmed qualitatively by UV–Vis. spectroscopy.

scholarly journals Structural Fragments Izopolivolframat–Anions and Gibbs Energy of Formation

2015 ◽  
Vol 16 (3) ◽  
pp. 524-527
Author(s):  
G.M. Rozantsev
Keyword(s):  
Mathematical Modeling ◽  
Gibbs Energy ◽  
Standard Gibbs Energy ◽  
Equilibrium Constants ◽  
Building Blocks ◽  
Pitzer Method ◽  
Titration Data ◽  
Thermodynamic Probability ◽  
Energy Of Formation ◽  
Concentration Constants

The method of mathematical modeling (program CLINP 2.1, Newton's method) on the basis of the pH-potentiometric titration data allowed to calculate concentration constants of isopolytungstate anions (IPTA) formation at different ionic forces (I = 0,01 ‑ 0,5 M). Thermodynamic constants of IPTA formation were obtained as a result of processing by Pitzer method using the concentration constans. The standard Gibbs energy of isopolytungstate anions formation were calculated. The last ones allowed to estimate the thermodynamic probability of the reactions, that can be used in the synthesis of salts containing these anions. The structure of known isopolytungstates can be built from the combination of such fragments: WO, W2O, W3O, W4O and W5O. The calculation of standard Gibbs energy of these fragments formation allowed to characterize the structure of hexatungstate-anion W6O20(OH)26-, which does not contain three terminal oxygen atoms. Such approach of using Gibbs energy of building blocks was recommended for prediction of equilibrium constants values in the mathematical modeling.

The reactions of oligoalcohols with arsenic, arsenous, boric and germanic acids

1980 ◽  
Vol 45 (10) ◽  
pp. 2645-2655 ◽  
Author(s):  
Antonín Mikan ◽  
Miloš Bartušek
Keyword(s):  
Aqueous Solutions ◽  
Equilibrium Constants ◽  
Dilute Aqueous Solutions

The reactions of sorbitol, mannitol, adonitol, dulcitol, glucose and glycerol with H3AsO4, H3AsO3, H3BO3 and GeO2 acids in dilute aqueous solutions were studied by potentiometric neutralization titrations. The formation of the following chelates was demonstrated: As(V)L3-, As(III)L(OH)2-, HAs(III)L(OH)2, BL2-, GeL2(OH)- and GeL32- and the equilibrium constants for their formation were found. Conditions for formation of these chelates of organic oligohydroxy compounds are discussed.

scholarly journals Investigations of ternary complexes of Co(II) and Ni(II) with thiodiacetate anion and 1,10-phenanthroline or 2,2’-bipyridine in aqueous solutions

2014 ◽  
Vol 13 (1) ◽  
Author(s):  
Dariusz Wyrzykowski ◽  
Joanna Pranczk ◽  
Dagmara Jacewicz ◽  
Aleksandra Tesmar ◽  
Bogusław Pilarski ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Substitution Reactions ◽  
Experimental Conditions ◽  
Kinetic Measurements ◽  
Hydroxo Complexes ◽  
Binary Complexes ◽  
Vis Spectroscopy ◽  
Potentiometric Titration Method ◽  
The Stability ◽  
Ph Range

AbstractA potentiometric titration method (PT) and a stopped-flow kinetic technique monitored by a UV−Vis spectroscopy have been used to characterize the stability of series of Co(II)- and Ni(II)-thiodiacetato complexes, M(TDA), in the presence of 1,10-phenanthroline (phen) or 2,2’-bipyridine (bipy) in aqueous solutions. The stability constants of the binary (1:1), ternary (1:1:1) as well as the resulting hydroxo complexes were evaluated and compared to the corresponding oxydiacetate complexes. Based on the species distribution as a function of pH the relative predominance of the species in the system over a pH range was discussed. Furthermore, the kinetic measurements of the substitution reactions of the aqua ligands to phen or bipy in the coordination sphere of the binary complexes M(TDA) were performed in the 288–303 K temperature range, at a constant concentration of phen or bipy and at seven different concentrations of the binary complexes (0.2–0.5 mM). The kinetic stability of the M(TDA) complexes was discussed in relation to the experimental conditions and the kind of the auxiliary ligands (phen/bipy). Moreover, the influence of the type of primary ligand (thiodiacetate/oxydiacetate) on the substitution rate of the auxiliary ligands was also compared.

scholarly journals Equilibrium constants and protonation site for N-methylbenzenesulfonamides

2011 ◽  
Vol 7 ◽  
pp. 1732-1738 ◽  
Author(s):  
José A Moreira ◽  
Ana M Rosa da Costa ◽  
Luis García-Río ◽  
Márcia Pessêgo
Keyword(s):  
Sulfuric Acid ◽  
Oxygen Atom ◽  
Electron Donor ◽  
Equilibrium Constants ◽  
Acidity Constants ◽  
Protonation Site ◽  
Protonation Equilibria ◽  
Vis Spectroscopy ◽  
Donor Character ◽  
Solvation Parameter

The protonation equilibria of four substituted N-methylbenzenesulfonamides, X-MBS: X = 4-MeO (3a), 4-Me (3b), 4-Cl (3c) and 4-NO2 (3d), in aqueous sulfuric acid were studied at 25 °C by UV–vis spectroscopy. As expected, the values for the acidity constants are highly dependent on the electron-donor character of the substituent (the pK BH+ values are −3.5 ± 0.2, −4.2 ± 0.2, −5.2 ± 0.3 and −6.0 ± 0.3 for 3a, 3b, 3c and 3d, respectively). The solvation parameter m* is always higher than 0.5 and points to a decrease in the importance of solvation on the cation stabilization as the electron-donor character of the substituent increases. Hammett plots of the equilibrium constants showed a better correlation with the σ+ substituent parameter than with σ, which indicates that the initial protonation site is the oxygen atom of the sulfonyl group.

scholarly journals Synthesis of Mn(II)-containing paratungstate B from aqueous solutions acidified by acetic acid

2021 ◽  
pp. 39-48
Keyword(s):  
Thermal Analysis ◽  
Acetic Acid ◽  
Aqueous Solutions ◽  
Equilibrium Constants ◽  
Background Electrolyte ◽  
Equilibrium Processes ◽  
Transformation Processes ◽  
Paratungstate B ◽  
Solution Acidity ◽  
Tungstate Anion

The method of pH-potentiometric titration and mathematical simulation were used to study the equilibrium processes in aqueous solutions of the WO42––CH3COOH–H2O system in the acidity range Z=(CH3COOH)/(Na2WO4)=0.8–1.7 at СW=0.01 mol L–1 and T=2980.1 K, a constant ionic strength being maintained by sodium nitrate as a background electrolyte ((NaNO3)=0.10 mol L–1). We developed the models of polyoxotungstate anions formation and the equilibrium transformation processes, which adequately describe experimental pH vs. Z dependences. It was found that acetic acid using to create the solution acidity that is necessary for the formation of isopoly tungstate anion contributes only to the formation of protonated paratungstate B anions Нх[W12O40(ОН)2](10–х)– (where x=0–4). We calculated the logarithms of the concentration equilibrium constants of the polyanion formation and plotted the distribution diagrams. Double sodium-manganese(II) paratungstate B Na8(H2O)28Mn(H2O)2[H2W12O42]4H2O was synthesized at Z=1.00 to confirm the results of the mathematical modeling. The chemical composition of the prepared salt was established by chemical elemental analysis, thermal analysis, FTIR spectroscopy, and single crystal X-ray analysis. The stepwise process of salt dehydration was studied by means of differential thermal analysis.

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