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1.
The solubility of rhodochrosite (MnCO3) at 25°C under constant carbon dioxide partial pressure p(CO2) was determined in NaCl solutions as a function of ionic strength I. The dissolution of MnCO3(s) for the reaction
has been determined as a function of pH. From these values, we have determined the equilibrium constant for the stoichiometric solubility of MnCO3(s) in NaCl solutions
These values have been fitted to the equation
with a standard error of = 0.1 with Iand concentrations in molalities. The extrapolated value of log K
o
sp(–10.3) in water is in good agreement with literature data (–10.1 to 10.8) determined in solutions of different composition and ionic strength. The measured values of the activity coefficient, T(Mn2+) and T(CO3
2–), have been used to estimate the stability constant for the formation of the MnCO3ion pair, K
*(MnCO3
0). The value of K
0(MnCO3
0) calculated from the values of K
*(MnCO3) by the Pitzer equation ( = 0.1) in this study (4.8 ± 0.1) is in reasonable agreement with literature data. 相似文献
2.
The equilibrium constant for the hydrolytic disproportionation of I2
has been determined at 25°C and at ionic strength 0.2 M(NaClO4) in buffered solution. The reaction was followed in the pH range where the equilibrium concentration of I2, I–, and IO3
–are commensurable, i.e., the fast equilibrium
is also established. The equilibrium concentrations of I2and I3
–were determined spectrophotometrically, and the concentrations of all the other species participating in process (1) were calculated from the stoichiometric constraints. The constants determined are \log K_1 = -47.61\pm 0.07 and \log K_2 = 2.86 \pm 0.01. 相似文献
3.
H. R. Galleguillos-Castro F. Hernández-Luis L. Fernández-Mérida M.A. Esteso 《Journal of solution chemistry》1999,28(6):791-807
Activity coefficients for sodium chloride in the NaCl + Na2SO4 + H2O ternary system were determined from emf measurements of the cell
at 15, 25, 35, and 45°C and at total ionic strengths from 0.1 to 6 mol-kg–1. These activity coefficient were analyzed by using the Harned rule and the treatments of Scatchard–Rush–Johnson and Pitzer. The analysis of activity coefficients at trace concentration was also achieved and qualitatively interpreted by considering the ionic interactions that can take place in the mixed system. Finally, the excess Gibbs energy of the mixtures was calculated and qualitatively analyzed against the composition of the system. 相似文献
4.
Solubility of Oxygen in Some 1-1, 2-1, 1-2, and 2-2 Electrolytes as a Function of Concentration at 25°C 总被引：1，自引：0，他引：1
The solubility of oxygen has been measured in a number of electrolytes [(LiCl, KCl, RbCl, CsCl, NaF, NaBr, NaI, NaNO3, KBr, KI, KNO3, CaCl2, SrCl2, BaCl2, Li2SO4, K2SO4, Mn(NO3)3)] as a function of concentration at 25°C. The solubilities, mol (kg-H2O)–1, have been fitted to a function of the molality m (standard deviation < 3mol-kg–1)
where A and B are adjustable parameters and the activity coefficient of oxygen )O2) = [O2]0/[O2]. The limiting salting coefficient, k
S = (ln / m)m=0 = A, was determined for all salts. The salting coefficients for the chlorides and sodium salts showed a near linear correlation with the crystal molar volume V
cryst = 2.52 r
3. The salting coefficients determined from the Scaled Particle Theory were in reasonable agreement with the measured values. The activity coefficients of oxygen in the solutions have been interpreted using the Pitzer equation
where
is a parameter that accounts for the interaction of O2 with cations (c) and anions (a) with molalities m
a and m
c, and
accounts for interactions for O2 with the cation and anion pair (c-a). The
and
coefficients determined for the most of the ions are in reasonable agreement with the tabulations of Clegg and Brimblecombe. The values of
for most of the ions are a linear function of the electrostriction molar volume (Velect = V0 – V
cryst). 相似文献
5.
The oxidation of H2NOH is first-order both in [NH3OH+] and [AuCl4
–]. The rate is increased by the increase in [Cl–] and decreased with increase in [H+]. The stoichiometry ratio, [NH3OH+]/[AuCl4
–], is 1. The mechanism consists of the following reactions.
The rate law deduced from the reactions (i)–(iv) is given by Equation (v) considering that [H+] K
a.
The reaction (iii) is a combination of the following reactions:
The activation parameters for the reactions (ii) and (iii) are consistent with an outer-sphere electron transfer mechanism. 相似文献
6.
Dubey Sapna Sharma Neetu Khandelwal Chandra L. Sharma Prem D. 《Transition Metal Chemistry》2003,28(2):176-181
The kinetics of osmium(VIII)-catalyzed oxidation of hypophosphite with hexacyanoferrate(III) in alkaline medium has been studied. The rate is independent of the concentration of the oxidant. The order with respect to hydroxide ion is variable. Rate law (1) conforms with the experimental observations.
The equilibrium constant 'K
1' for step (2)
has been evaluated kinetically to be (21 ± 5.0), (23 ± 5.0), (26 ± 6) and (32 ± 6) at 25, 30, 32 and 35 °C and I = 1.0 mol dm–3 respectively. The energy and entropy of activation were calculated to be (42 ± 2.0) kJ mol–1 and (82 ± 6.0) J K–1 mol–1 respectively. A plausible reaction mechanism has been suggested. 相似文献
7.
The thermal decomposition of zirconium oxyhydroxides prepared by the mixture of aqueous zirconium oxychloride solutions and aqueous solutions of sodium hydroxide or ammonium hydroxide under various conditions has been examined by thermogravimetry, differential thermal analysis, X-ray diffraction study and infrared spectrophotometry. As a result, it is seen that the thermal decomposition of zirconium oxyhydroxide, in which the composition is ZrO2-x(OH)2xyH2O where x2 and 1y<2, proceeds according to the following process:
This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
8.
Jia-Zhen Yang Dian-Zhen Lu Hong-Chang Li Chao-Jun Hou 《Journal of solution chemistry》2003,32(6):559-567
The determination of the second dissociation constant of carbonic acid K
2 in 5, 15, and 25 mass% ethanol—water mixed solvents has been made using cell of the type:
at 5 to 45°C. From these data, thermodynamic quantities, dissociation enthalpy, and dissociation entropy were determined. The dependence of pK
2 on dielectric constant of the mixed solvents is discussed in term of the Beveridge model. 相似文献
9.
Dissociation Constants for Citric Acid in NaCl and KCl Solutions and their Mixtures at 25 °C 总被引：1，自引：0，他引：1
The constants for the dissociation of citric acid (H3C) have been determined from potentiometric titrations in aqueous NaCl and KCl solutions and their mixtures as a function of ionic strength (0.05–4.5 mol-dm–3) at 25 °C. The stoichiometric dissociation constants (Ki*)
were used to determine Pitzer parameters for citric acid (H3C), and the anions, H2C–, HC2–, and C3–. The thermodynamic constants (Ki) needed for these calculations were taken from the work of R. G. Bates and G. D. Pinching (J. Amer. Chem. Soc. 71, 1274; 1949) to fit to the equations (T/K):
The values of Pitzer interaction parameters for Na+ and K+ with H3C, H2C–, HC2–, and C3– have been determined from the measured pK values. These parameters represent the values of pK1*, pK2*, and pK3*, respectively, with standard errors of = 0.003–0.006, 0.015–0.016, and 0.019–0.023 for the first, second, and third dissociation constants. A simple mixing of the pK* values for the pure salts in dilute solutions yield values for the mixtures that are in good agreement with the measured values. The full Pitzer equations are necessary to estimate the values of pKi* in the mixtures at high ionic strengths. The interaction parameters found for the mixtures are Na-K – H2C = – 0.00823 ± 0.0009; Na-K – HC = – 0.0233 ± 0.0009, and Na-K – C = 0.0299 ± 0.0055 with standard errors of (pK1) = 0.011, (pK2) = 0.011, and (pK3) = 0.055. 相似文献
10.
Rosso Janina A. Villata Laura S. Mártire Daniel O. Capparelli Alberto L. 《Transition Metal Chemistry》1998,23(5):645-648
The molecular oxygen-mediated decomposition of the binuclear complex, prepared from oxomolybdate(V) and L-(+)-cysteine, was studied spectrophotometrically at pH 3.5–5.6. The formation of MoVI was detected. The effects of pH and [O2] on the decomposition kinetics are given by the equation:
with the apparent first order rate constant, kobs, expressed in s–1 and the concentrations in molar units. 相似文献
11.
Khan Zaheer Rafiquee Mohammad Z. A. Niaz Mohammad A. Khan Abdul Aziz Kabir-ud-Din 《Transition Metal Chemistry》1998,23(5):537-540
The kinetics of alkaline hydrolysis of Co(Asn)2, yielding Co(OH)2, NH3 and aspartic acid, have been studied spectrophotometrically, and the effects of CoII and NaOH concentrations on the reaction rate determined. The rate increases with increasing [NaOH], whereas variation of [CoII] has no significant effect. The kinetics of NH3 evolution conform to the rate law:
It is proposed that the reaction proceeds through formation of a dianionic tetrahedral intermediate. 相似文献
12.
The enthalpies and entropies of evaporation of Al(CH3)3–Sn(CH3)4and Ga(CH3)3–Sn(CH3)4solutions were determined. It was established that solvates are formed in these systems and that the dissociation energies of specific interactions in them change in the following order:
(10.3) >
>
>
(4.08 kJ mol–1),
(6.52) >
(5.14) >
>
(4.08 kJ mol–1). 相似文献
13.
Leopoldo Ceraulo Serena Fanara Angela Ruggirello Vincenzo Turco Liveri 《Journal of Cluster Science》2007,18(4):883-895
The state of the water-soluble salt iron(III) chloride in AOT reverse micelles dispersed in carbon tetrachloride has been
investigated by FT-IR spectroscopy. Interestingly, while the entrapment of a lot of water-soluble inorganic salts in AOT reverse
micelles requires preliminarily the presence of significant amounts of water within the micellar core, solubilization of FeCl3 occurs without the need to add water in the micellar solution reaching the very high solubility value, expressed as the maximum
salt-to-surfactant molar ratio, of 1.30. The analysis of the spectral features of the investigated samples leads to hypothesize
that iron(III) chloride is confined within the reverse micellar core as small size melted clusters of ionic species arising
from the reactions
accompanied by a marked structural rearrangement of the AOT head group domain surrounding the micellar core and a shift of
the sodium counterion from the micellar core surface to its interior. This picture has been further corroborated by conductivity
measurements of FeCl3/AOT/CCl4 solutions as a function of the salt-to-surfactant molar ratio. 相似文献
14.
Electron transfer mediation to an anode, whose potential is judiciously controlled, provides the conceptual basis for the development of novel chronoamperometric biosensors. The mediators are appropriately selected redox couples (Ox/Red) which are amenable to recycling in the following type of enzyme E catalyzed reaction sequence
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相似文献
15.
A new method of measuring the pH of high-temperature aqueous solutions using optical indicators was developed. The absorbance spectrum of acridine changes as a function of pH, allowing its use as an optical indicator for pH. The pKa of acridine were experimentally determined in KOH-AcOH pH-buffer solutions at temperatures from 5 to 250°C at vaporsaturated pressures:
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