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1.
The hydrolysis of (C2H5)2Sn2+, (C2H5)3Sn+ and (n‐C3H7)3Sn+ has been studied, by potentiometric measurements ([H+]‐glass electrode), in NaNO3, NaCl, NaCl/Na2SO4 mixtures and in a synthetic seawater (SSWE), as an ionic medium simulating the major composition of natural seawater, at different ionic strengths (0 ≤ I ≤ 5 mol dm?3) and salinities (15 ≤ S ≤ 45), and at t = 25 °C. Five hydrolytic species for (C2H5)2Sn2+, three for (C2H5)3Sn+ and two for (C3H7)3Sn+ are found. Interactions with the anion components of SSWE, considered as single‐salt seawater, are determined by means of a complex formation model. A predictive equation for the calculation of unknown hydrolysis constants of trialkyltin(IV) cations, such as tributyltin(IV), in NaNO3, NaCl, and SSWE media at different ionic strengths is proposed. Equilibrium constants obtained are also used to determine the interaction parameters of Pitzer equations. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
2.
Concetta De Stefano Claudia Foti Antonio Gianguzza Francesca Marrone Silvio Sammartano 《应用有机金属化学》1999,13(11):805-811
The hydrolysis of methyltin(IV) trichloride (CH3SnCl3) has been studied in aqueous NaCl and NaNO3 solutions (0 < I/mol dm−3 ≤ 1), at different temperatures (15 ≤ T/°C ≤ 45) bypotentiometric measurements (H+‐glass electrode). By considering the generic hydrolytic <?tw=97.2%>reaction pCH3Sn3+ + qH2O = (CH3Sn)p(OH)q3p−q<?tw>+ qH+ (logβpq), we have the formation of five species and logβ12 = −3.36, logβ13 = −8.99, logβ14 = −20.27 and logβ25 = −7.61. The first hydrolysis step is measurable only at very low pH values and was not determined: a rough estimate of the hydrolysis constant is logβ11 = −1.5 (± 0.5). The dependence on ionic strength of logβpq is quite different in NaNO3 and NaCl solutions, and the formation at low pH values of the species CH3Sn(OH)Cl+ has been found with logβ = −1.40. Hydrolysis constants strongly depend on temperature and from the relationships logβpq = f(T), ΔH ° values have been calculated. Speciation problems of CH3Sn3+ in aqueous solution are discussed. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
3.
4.
J. M. Santana-Casiano M. González-Dávila F. J. Millero 《Journal of solution chemistry》2008,37(6):749-762
The stability constants for the hydrolysis of Cu(II) and formation of chloride complexes in NaClO4 solution, at 25 °C, have been examined using the Pitzer equations. The calculated activity coefficients of CuOH+, Cu(OH)2, Cu2(OH)3+, Cu2(OH)22+, CuCl+ and CuCl2 have been used to determine the Pitzer parameter (β
i
(0), β
i
(1), and C
i
) for these complexes. These parameters yield values for the hydrolysis constants (log 10
β
1*, log 10
β
2*, log 10
β
2,1* and log 10
β
2,2*) and the formation of the chloride complexes (log 10
β
CuCl* and
that agree with the experimental measurements, respectively to ±0.01,±0.02,±0.03,±0.06,±0.03 and ±0.07.
The stability constants for the hydrolysis and chloride complexes of Cu(II) were found to be related to those of other divalent
metals over a wide range of ionic strength. This has allowed us to use the calculated Pitzer parameters for copper complexes
to model the stability constants and activity coefficients of hydroxide and chloride complexes of other divalent metals. The
applicability of the Pitzer Cu(II) model to the ionic strength dependence of hydrolysis of zinc and cadmium is presented.
The resulting thermodynamic hydroxide and chloride constants for zinc are
and
. For cadmium the thermodynamic hydrolysis constants are
and
. The Cu(II) model allows one to determine the stability of other divalent metal complexes over a wide range of concentration
when little experimental data are available. More reliable stepwise stability constants for divalent metals are needed to
test the linearity found for the chloro complexes. 相似文献
5.
Ultraviolet absorbance spectra of ferric ions in 0.68m NaClO4 were studied as a function of pH at 4.0, 14.9, and 25.0°C. The results provided an evaluation of the stability constant for the formation of FeOH2+ which is *1=[FeOH
+][H
+]/[Fe
3+]. The enthalpy change for the reaction Fe3++H2O FeOH2++H+ was calculated as 10.0±0.3 kcal-mole–1. Increasing temperature was also found to promote the reaction Fe3++2H2O Fe(OH)
2
+
+2H+. Our results were combined with the results of other to produce an expression describing the first hydrolysis equilibrium at ionic strengths between 0 and 3m and temperatures between 4.0 and 45.0°C at 1 atm total pressure. At 25°C and 0.68m the ionic strength *1=1.90×10-3 相似文献
6.
Elham M. Abd-Alla 《Monatshefte für Chemie / Chemical Monthly》2003,134(9):1177-1184
Summary. Equilibria studies in aqueous solution containing 25% dioxane (V/V) are reported for dimethyltin(IV) and trimethyltin(IV) (M) complexes with some imidazole derivatives (L). Stoichiometry and stability constants for the complexes formed were determined at 25°C and ionic strength 0.1M NaNO3. The results of the dimethyltin(IV) complexes showed the best fit of the titration curves when complexes ML, ML
2, ML
2H–1, and ML
2H–2 were expected beside the hydrolysis products of the dimethyltin(IV) cation, while the calculations of the trimethyltin(IV) complexes reported the presence of only the complexes ML, MLH–1, and the hydrolysis products of the trimethyltin(IV) cation. The concentration distribution of each species of the complexes in solution was evaluated. The stability of all complexes formed was investigated and discussed in terms of molecular structure of the ligand imidazole and the nature of the alkyltin cation. It is deduced that the stability of the complex formed increases as the basicity of the ligand imidazole is increased. On the other hand, the trimethyltin(IV) cation has a very low ability to form complexes compared to the dimethyltin(IV) cation.Received November 22, 2002; accepted (revised) March 3, 2003
Published online August 18, 2003 相似文献
7.
Hydrolysis constants of protactinium(V) at tracer scale were deduced from the variations of partition coefficient of Pa(V) in the system: TTA/toluene/Pa(V)/H2O/H+/Na+/ClO–
4, as a function of TTA and proton concentrations, ionic strength (0.1 3 M), and temperature (10 60°C). Extrapolations of theses constants to zero ionic strength were performed using the SIT model. Standard thermodynamic data (under atmospheric pressure) related to the two hydrolysis equilibria involved, were derived from the temperature dependence of the hydrolysis constants at infinite dilution. 相似文献
8.
Pasquale Crea Concetta De Stefano Mutsa Kambarami Frank J. Millero Virender K. Sharma 《Journal of solution chemistry》2008,37(9):1245-1259
The protonation constants for oxidized glutathione, H
i−1L(4−i+1)−, K
i
H=[H
i
L(4−i)−]/[H
i−1L(4−i+1)−][H+] i=1,2,…,6 have been measured at 5, 25 and 45 °C as a function of the ionic strength (0.1 to 5.4 mol⋅[kg(H2O)]−1) in NaCl solutions. The effect of ionic strength on the measured protonation constants has been used to determine the thermodynamic
values (K
i
H0) and the enthalpy (ΔH
i
) for the dissociation reaction using the SIT model and Pitzer equations. The SIT (ε) and Pitzer parameters (β
(0), β
(1) and C) for the dissociation products (L4−, HL3−, H2L2−, H3L−, H4L, H5L+, H6L2+) have been determined as a function of temperature. These results can be used to examine the effect of ionic strength and
temperature on glutathione in aqueous solutions with NaCl as the major component (body fluids, seawater and brines). 相似文献
9.
An aqueous thermodynamic model is developed, which accurately describes the effects of Na+ complexation, ionic strength, carbonate concentration, and temperature on the complexation of Sr2+ by ethylenedinitrilotetraacetic acid (EDTA) under basic conditions. The model is developed from the analysis of literature data on apparent equilibrium constants, enthalpies, and heat capacities, as well as on an extensive set of solubility data on SrCO3(c) in the presence of EDTA obtained as part of this study. The solubility data for SrCO3(c) were obtained in solutions ranging in Na2CO3 concentration from 0.01 to 1.8 m, in NaNO3 concentration from 0 to 5 m, and at temperatures extending to 75C. The final aqueous thermodynamic model is based upon the equations of Pitzer and requires the inclusion of a NaEDTA3– species. An accurate model for the ionic strength dependence of the ion-interaction coefficients for the SrEDTA2– and NaEDTA3–aqueous species allows the extrapolation of standard state equilibrium constants for these species, which are significantly different from the 0.1 m reference state values available in the literature. The final model is tested by application to chemical systems containing competing metal ions (i.e., Ca2+) to further verify the proposed model and indicate the applicability of the model parameters to chemical systems containing other divalent metal-EDTA complexes. 相似文献
10.
Robert C. Moore Marian Borkowski Michael G. Bronikowski Jianfeng Chen Oleg S. Pokrovsky Yuanxian Xia Gregory R. Choppin 《Journal of solution chemistry》1999,28(5):521-531
The stability constants of NpO
2
+
, UO
2
2+
Am3+, and Th4+ with acetate and lactate anions has been measured in 0.3–5.0m NaCl media at 25°C by the solvent extraction technique. For the 1:1 complexation, the values of the stability constants increased in the order: NpO
2
+
< Am3+ <
2
2+
< Th4+, in accordance with the actinide charge density and reflecting the strongly ionic bonding of the complexes. The Pitzer ionic interaction parameters were calculated and used to estimate the thermodynamic stability constants at I = 0. Because our data were collected mainly in the high ionic strength region values of (1) were estimated from values reported in the literature. For all stability constants the Pitzer model gives an excellent representation of the data using three interaction parameters (0), (1), and COn leave from Institute of 相似文献
11.
G. E. Boyd 《Journal of solution chemistry》1977,6(3):135-148
Osmotic coefficients for aqueous mixtures of sodium chloride with benzyltrimethylammonium chloride, BzMe3NCl, obtained by the gravimetric isopiestic vapor pressure comparison method are interpreted with the McKay-Perring transform, with the Scatchard neutral electrolyte treatment, and with the Pitzer ion-component equations. Molal ionic and mean ionic activity coefficients for Na+ and Cl– ions and for NaCl, respectively, in these mixtures at unit total ionic strength also were determined with an electrochemical cell. The excess free energy chenges Gex on mixing NaCl with BzMe3NCl were estimated and employed to gain an insight into the relative importance of like and unlike cation-cation interactions. 相似文献
12.
Frank J. Millero Sara Sotolongo David J. Stade Carmen A. Vega 《Journal of solution chemistry》1991,20(11):1079-1092
The oxidation of Fe(II) with H2O2 has been measured in NaCl and NaClO4 solutions as a function of pH, temperature T (K) and ionic strength (M, mol-L–1). The rate constants, k (M–1-sec–1), d[Fe(II)]/DT=-k[Fe(II)][2O2]at pH=6.5 have been fitted to equations of the formlog k = log k0+ AI
1/2+BI+CI
1/2/T
Where log k0=15.53-3425/T in water; A=–2.3, –1.35; B=0.334, 0.180; and C=391, 235, respectively, for NaCl (=0.09) and NaClO4 ( =0.08). Measurements made in NaCl solutions with added anions yield rates in the order B(OH)
4
–
>HCO
3
–
>ClO
4
–
>Cl–>NO
3
–
>SO
4
2–
and are attributed to the relative strength of the interactions of Fe2+ or FeOH+ with these anions. The FeB(OH)
4
+
species is more reactive while the FeCO
3
0
, FeCl+, FeNO
3
+
and FeSO
4
0
species are less reactive than the FeOH+ ion pair. The general trend is similar to our earlier studies of the oxidation of Fe(II) with O2 except for B(OH)
4
–
. The effect of pH on the logk was found to be a quadratic function of the concentration of H+ or OH– from pH=4 to 8. These results have been attributed to the different rate constants for Fe2+ (k0) and FeOH+ (k1) which are related to the measured k by, k=k0Fe + k1FeOH, where i is the molar fraction of species i. The rates increase due to the greater reactivity of FeOH+ compared to Fe2+. k0 is independent of composition and ionic strength but k1 is a function of ionic strength and composition due to the interactions of FeOH+ with various anions. 相似文献
13.
The kinetics of oxidation of tartaric acid by Ce(IV) in the absence and presence of acrylamide has been investigated spectrophotometrically in aqueous H2SO4–HClO4 media at a constant ionic strength 2.0M and 25°C. Oxidation of tartaric acid in both cases was first order with respect to Ce(IV). Kinetic data showed that the reaction involves the formation of an unstable complex and an intermediate free radical. The activation parameters were calculated to be E
a
=91.3±0.4 kJ-mol–1, S=20.2±1.0 J-mol–1-K–1, H=88.8±0.4 kJ-mol–1. A polymerization mechanism is discussed. 相似文献
14.
The rates of oxidation of Fe(II) in NaCl and NaClO
4
solutions were studied as a function of pH (6 to 9), temperature (5 to 25°C), and ionic strength (0 to 6m). The rates are second order with respect to [H+] or [OH–] and independent of ionic strength and temperature. The overall rate of the oxidation is given by
相似文献
15.
Fe(III) hydrolysis and fluoride complexation behavior was examined in 0.68 molal sodium perchlorate at 25°C. Our assessment of the complexation of Fe(III) by fluoride ions produced the following results: logF1 = 5.155, logF2 = 9.107, logF3 = 11.96, logF4 = 13.75, where logFn = 5.155=[FeF
n
(3-n)+
][Fe3+]–1[F–]–n. The stepwise fluoride complexation constants,FK
n+1, obtained in our work (where logF
K
n+1 =logFn) indicate that K
n+1/K
n
=0.072±0.01. Formation constants for equilibria, Fe3++nH2OFe(OH)
n
(3–n)+
+nH+, expressed in the form
n
*
[Fe(OH)
n
(3-n)+
][H+]n
,[Fe
3+]-1, were estimated as
1
*
= –2.754, and
2
*
–7. Our study indicates that the results of previous hydrolysis investigations include very large overestimates of Fe(OH)
2
+
formation constants. 相似文献
16.
When the sodium ion (Na+) concentration is increased above 0.5 mol-dm−3 (M), the concentrations of dissolved silica in aqueous sodium chloride (NaCl) and sodium nitrate (NaNO3) solutions decrease because of the salting out effect. On the other hand, the concentration of the dissolved silica in aqueous sodium sulfate (Na2SO4) solutions increases monotonously as the concentration of Na+ is increased above 0.5 M. The purpose of this study is to determine the reasons why the salting-out effect is not observed in Na2SO4 solutions. FAB-MS (Fast Atom Bombardment Mass Spectrometry) was used to sample directly the silica species dissolved in aqueous Na2SO4, NaCl, and NaNO3 solutions. In the FAB-MS spectra of these solutions, the peak intensity ratios of the linear tetramer to the cyclic tetramer largely increased for Na+ concentrations between (0.1 and 1) M. This shows that some characteristics of the Na2SO4 solutions are similar to those of the NaCl and NaNO3 solutions. In Na2SO4 solutions, however, when the concentration of Na+ is higher than 1 M, the peak intensity of the dimer is much higher than those of the other silicate complexes. In Na2SO4 solutions, the SO42− ion undergoes partial hydrolysis to form HSO−4 and OH− is produced. In particular, in the range where the concentration of SO42− is high, the pH of the solution increases slightly. This higher pH yields more dimers from the hydrolysis of silicate complexes. This increase in dimer production agrees with the observation that silica dissolves in sodium hydroxide (NaOH) solutions mainly as a dimer when the concentration of NaOH is less than 0.1 M. In Na2SO4 solutions at high concentrations, a salting-out effect is not observed for silica. This is due to the increase in the concentration of OH−, which accelerates the hydrolysis of silica and results in dimer formation. 相似文献
17.
Rao L Tian G Di Bernardo P Zanonato P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(39):10985-10993
The hydrolysis of PuVI was studied at variable temperatures (283–343 K) by potentiometry, microcalorimetry, and spectrophotometry. Three hydrolysis reactions, mPuO22++nH2O=(PuO2)m(OH)n+nH+), in which (n,m)=(1,1), (2,2), and (5,3), were invoked to describe the potentiometric and calorimetric data. The equilibrium constants (*βn,m) were determined by potentiometry at 283, 298, 313, 328, and 343 K. As the temperature was increased from 283 to 343 K, *β1,1, *β2,2, and *β5,3, increased by 1, 1.5, and 4 orders of magnitude, respectively. The enhancement of hydrolysis at elevated temperatures is mainly due to the significant increase of the degree of ionization of water as the temperature increases. Measurements by microcalorimetry indicate that the three hydrolysis reactions are all endothermic at 298.15 K, with enthalpies of (35.0±3.4) kJ mol?1, (65.4±1.0) kJ mol?1, and (127.7±1.7) kJ mol?1 for ΔH1,1, ΔH2,2, and ΔH5,3, respectively. The hydrolysis constants at infinite dilution have been obtained with the Specific Ion Interaction approach. The applicability of three approaches for estimating the equilibrium constants at different temperatures, including the constant enthalpy approach, the DQUANT equation, and the Ryzhenko–Bryzgalin model, were evaluated with the data from this work. 相似文献
18.
De Stefano C Milea D Pettignano A Sammartano S 《Analytical and bioanalytical chemistry》2003,376(7):1030-1040
The acid–base properties of phytic acid [myo-inositol 1,2,3,4,5,6-hexakis(dihydrogen phosphate)] (H12Phy; Phy12–=phytate anion) were studied in aqueous solution by potentiometric measurements ([H+]-glass electrode) in lithium and potassium chloride aqueous media at different ionic strengths (0<I mol L–13) and at t=25 °C. The protonation of phytate proved strongly dependent on both ionic medium and ionic strength. The protonation constants obtained in alkali metal chlorides are considerably lower than the corresponding ones obtained in a previous paper in tetraethylammonium iodide (Et4NI; e.g., at I=0.5 mol L–1, logK3H=11.7, 8.0, 9.1, and 9.1 in Et4NI, LiCl, NaCl and KCl, respectively; the protonation constants in Et4NI and NaCl were already reported), owing to the strong interactions occurring between the phytate and alkaline cations present in the background salt. We explained this in terms of complex formation between phytate and alkali metal ions. Experimental evidence allows us to consider the formation of 13 mixed proton–metal–ligand complexes, MjHiPhy(12–i–j)–, (M+=Li+, Na+, K+), with j7 and i6, in the range 2.5pH10 (some measurements, at low ionic strength, were extended to pH=11). In particular, all the species formed are negatively charged: i+j–12=–5, –6. Very high formation percentages of M+–phytate species are observed in all the pH ranges investigated. The stability of alkali metal complexes follows the trend Li+Na+K+. Some measurements were also performed at constant ionic strength (I=0.5 mol L–1), using different mixtures of Et4NI and alkali metal chlorides, in order to confirm the formation of hypothesized and calculated metal–proton–ligand complex species and to obtain conditional protonation constants in these multi-component ionic media.Presented at SIMEC–02, Santiago de Compostela, 2–6 June 2002 相似文献
19.
Donald R. Schreiber James Huebner Seyed Rahmani Frank J. Millero 《Journal of solution chemistry》1993,22(3):201-210
Enthalpies of mixing (m
H) aqueous solutions of CoCl2, CuCl2, and MnCl2 with NaCl solutions were measured at constant ionic strengths of 0.5, 1.0, and 3.0 molal at 25°C. The excess enthalpy equations of Pitzer were then fit to the resulting m
H data. The resulting parameters are the temperature derivatives of the activity coefficient mixing parameters in the Pitzer system. The heat of mixing data for CoCl2 and CuCl2 were in agreement with earlier isomolal results by other workers. 相似文献
20.
Donald R. Schreiber De Von Andres James Huebner Seyed Rahmani 《Journal of solution chemistry》1993,22(5):457-467
The heat of dilution of aqueous solutions of ZnCl2 and the heats of mixing H
m
of aqueous solutions of CdCl2, NiCl2, and ZnCl2 with NaCl solutions were measured at 25°C. The heats of mixing were made at constant ionic strengths of 0.5, 1.0, and 3.0 molal. The excess enthalpy equations of Pitzer were then fitted to the resulting heats of dilution and heats of mixing data. The resulting parameters are the temperature derivatives of the activity coefficient mixing parameters in the Pitzer system. 相似文献
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