共查询到20条相似文献,搜索用时 31 毫秒
1.
Low-lying structures of water cationic clusters and the compounds with the OH radical have become a hot topic in recent years. We here investigate the cluster \( {\left({\mathrm{H}}_2\mathrm{O}\right)}_{10}^{+} \) and calculate its ideal structures by the quantum chemical calculation together with the particle swarm optimization method. We analyzed the properties of the obtained lower-energy isomers of \( {\left({\mathrm{H}}_2\mathrm{O}\right)}_{10}^{+} \). Their energies are further re-optimized and demonstrated at three different methods with two basis sets. Based on our numerical calculations, a new cage-like structure of \( {\left({\mathrm{H}}_2\mathrm{O}\right)}_{10}^{+} \) with the lowest energy is obtained at MP2/aug-cc-pVDZ level. Our results showed the comparison of energy order at different conditions and demonstrated the influence of temperature on the relative Gibbs energy and IR spectra. Moreover, we also contained the molecule orbitals to discuss the stability of these representative isomers. 相似文献
2.
The molar enthalpies of solution of 2-aminopyridine at various molalities were measured at T=298.15 K in double-distilled water by means of an isoperibol solution-reaction calorimeter. According to Pitzer’s theory,
the molar enthalpy of solution of the title compound at infinite dilution was calculated to be DsolHm¥ = 14.34 kJ·mol-1\Delta_{\mathrm{sol}}H_{\mathrm{m}}^{\infty} = 14.34~\mbox{kJ}\cdot\mbox{mol}^{-1}, and Pitzer’s ion interaction parameters bMX(0)L, bMX(1)L\beta_{\mathrm{MX}}^{(0)L}, \beta_{\mathrm{MX}}^{(1)L}, and CMXfLC_{\mathrm{MX}}^{\phi L} were obtained. Values of the relative apparent molar enthalpies (
φ
L) and relative partial molar enthalpies of the compound ([`(L)]2)\bar{L}_{2}) were derived from the experimental enthalpies of solution of the compound. The standard molar enthalpy of formation of the
cation C5H7N2 +\mathrm{C}_{5}\mathrm{H}_{7}\mathrm{N}_{2}^{ +} in aqueous solution was calculated to be DfHmo(C5H7N2+,aq)=-(2.096±0.801) kJ·mol-1\Delta_{\mathrm{f}}H_{\mathrm{m}}^{\mathrm{o}}(\mathrm{C}_{5}\mathrm{H}_{7}\mathrm{N}_{2}^{+},\mbox{aq})=-(2.096\pm 0.801)~\mbox{kJ}\cdot\mbox{mol}^{-1}. 相似文献
3.
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
4.
Henri Schmit Christoph Rathgeber Peter Hennemann Stefan Hiebler 《Journal of Thermal Analysis and Calorimetry》2014,117(2):595-602
A three-step method to determine the eutectic composition of a binary or ternary mixture is introduced. The method consists in creating a temperature–composition diagram, validating the predicted eutectic composition via differential scanning calorimetry and subsequent T-History measurements. To test the three-step method, we use two novel eutectic phase change materials based on \(\mathrm{Zn}(\hbox {NO}_3)_2\cdot 6\mathrm{H}_{2}{\mathrm O}\) and \(\mathrm{NH}_4\mathrm{NO}_3\) respectively \(\mathrm{Mn}(\hbox {NO}_3)_2\cdot 6\mathrm{H}_{2}{\hbox {O}}\) and \(\mathrm{NH}_4\mathrm{NO}_3\) with equilibrium liquidus temperatures of 12.4 and 3.9 \(\,^{\circ }\mathrm {C}\) respectively with corresponding melting enthalpies of 135 J \(\mathrm{g}^{-1}\) (237 J \(\mathrm{cm}^{-3}\) ) respectively 133 J \(\mathrm{g}^{-1}\) (225 J \(\mathrm{cm}^{-3}\) ). We find eutectic compositions of 75/25 mass% for \(\mathrm{Zn}(\hbox {NO}_3)_2\cdot \mathrm{6H}_{2}{\mathrm{O}}\) and \(\mathrm{NH}_4\mathrm{NO}_3\) and 73/27 mass% for \(\mathrm{Mn}(\hbox {NO}_3)_2\cdot 6\mathrm{H}_{2}{\mathrm{O}}\) and \(\mathrm{NH}_4\mathrm{NO}_3\) . Considering a temperature range of 15 K around the phase change, a maximum storage capacity of about 172 J \(\mathrm{g}^{-1}\) (302 J \(\mathrm{cm}^{-3}\) ) respectively 162 J \(\mathrm{g}^{-1}\) (274 J \(\mathrm{cm}^{-3}\) ) was determined for \(\mathrm{Zn}(\hbox {NO}_3)_2\cdot \mathrm{6H}_{2}{\mathrm{O}}\) and \(\mathrm{NH}_4\mathrm{NO}_3\) respectively \(\mathrm{Mn}(\hbox {NO}_3)_2\cdot \mathrm{6H}_{2}{\mathrm{O}}\) and \(\mathrm{NH}_4\mathrm{NO}_3\) . 相似文献
5.
K. Sharanabasamma Mahantesh A. Angadi Manjalee S. Salunke Suresh M. Tuwar 《Journal of solution chemistry》2012,41(2):187-199
The kinetics of oxidation of L-valine by a copper(III) periodate complex was studied spectrophotometrically. The inverse second-order
dependency on [OH−] was due to the formation of the protonated diperiodatocuprate(III) complex ([Cu(H3IO6)2]−) from [Cu(H2IO6)2]3−. The retarding effect of initially added periodate suggests that the dissociation of copper(III) periodate complex occurs
in a pre-equilibrium step in which it loses one periodate ligand. Among the various forms of copper(III) periodate complex
occurring in alkaline solutions, the monoperiodatocuprate(III) appears to be the active form of copper(III) periodate complex.
The observed second-order dependency of [L-valine] on the rate of reaction appears to result from formation of a complex with
monoperiodatocuprate(III) followed by oxidation in a slow step. A suitable mechanism consistent with experimental results
was proposed. The rate law was derived as:
- \fracd[DPC]dt = \frackK1K2K3[Cu(H2IO6)2]f3- [L -Val]f2[H3IO62 -]f[OH - ]f2.- \frac{\mathrm{d}[\mathrm{DPC}]}{\mathrm{d}t} =\frac{kK_{1}K_{2}K_{3}[\mathrm{Cu}(\mathrm{H}_{2}\mathrm{IO}_{6})_{2}]_{\mathrm{f}}^{3-} [\mathrm{L} -\mathrm{Val}]_{\mathrm{f}}^{2}}{[\mathrm{H}_{3}\mathrm{IO}_{6}^{2 -}]_{\mathrm{f}}[\mathrm{OH}^{ -} ]_{\mathrm{f}}^{2}}. 相似文献
6.
The acid?Cbase behavior of $\mathrm{Fe}(\mathrm{CN})_{6}^{4-}$ was investigated by measuring the formal potentials of the $\mathrm{Fe}(\mathrm{CN})_{6}^{3-}$ / $\mathrm{Fe}(\mathrm{CN})_{6}^{4-}$ couple over a wide range of acidic and neutral solution compositions. The experimental data were fitted to a model taking into account the protonated forms of $\mathrm{Fe}(\mathrm{CN})_{6}^{4-}$ and using values of the activities of species in solution, calculated with a simple solution model and a series of binary data available in the literature. The fitting needed to take account of the protonated species $\mathrm{HFe}(\mathrm{CN})_{6}^{3-}$ and $\mathrm{H}_{2}\mathrm{Fe}(\mathrm{CN})_{6}^{2-}$ , already described in the literature, but also the species $\mathrm{H}_{3}\mathrm{Fe}(\mathrm{CN})_{6}^{-}$ (associated with the acid?Cbase equilibrium $\mathrm{H}_{3}\mathrm{Fe}(\mathrm{CN})_{6}^{-}\rightleftharpoons \mathrm{H}_{2}\mathrm{Fe}(\mathrm{CN})_{6}^{2-} + \mathrm{H}^{+}$ ). The acidic dissociation constants of $\mathrm{HFe}(\mathrm{CN})_{6}^{3-}$ , $\mathrm{H}_{2}\mathrm{Fe}(\mathrm{CN})_{6}^{2-}$ and $\mathrm{H}_{3}\mathrm{Fe}(\mathrm{CN})_{6}^{-}$ were found to be $\mathrm{p}K^{\mathrm{II}}_{1}= 3.9\pm0.1$ , $\mathrm{p}K^{\mathrm{II}}_{2} = 2.0\pm0.1$ , and $\mathrm{p}K^{\mathrm{II}}_{3} = 0.0\pm0.1$ , respectively. These constants were determined by taking into account that the activities of the species are independent of the ionic strength. 相似文献
7.
H. Lopez-Gonzalez J. R. Peralta-Videa E. T. Romero-Guzman A. Rojas-Hernandez J. L. Gardea-Torresdey 《Journal of solution chemistry》2010,39(4):522-532
The determination of equilibrium constants is difficult when several chemical species are simultaneously present in solution.
In this investigation, optical emission spectroscopic determinations of chromium(III) concentration in a 10−4 mol⋅dm−3 solution, prepared from K2Cr2O7 reduced in HNO3 or HCl media, were used to construct the pCr(aq)–pC
H diagram. This diagram was used to calculate the pC
H borderline of precipitation, to estimate the solubility product (log10Ksp,Cr(OH)3*)(\log_{10}K_{\mathrm{sp,Cr(OH)}_{3}}^{*}), and the hydrolysis constants (log10bCr,H*,log10bCr,2H*(\log_{10}\beta_{\mathrm{Cr,H}}^{*},\log_{10}\beta_{\mathrm{Cr,2H}}^{*}, and log10bCr,3H*)\log_{10}\beta_{\mathrm{Cr,3H}}^{*}) of Cr(III). The hydrolysis constants were also calculated using the SQUAD and SUPERQUAD software, along with the average
ligand number method. UV-Vis absorption data and associated variables were used in SQUAD, SUPERQUAD, and the average ligand
calculations. Results are: 9.00±0.04 for the pC
H at the onset of precipitation, 12.40 for log10Ksp,Cr(OH)3*\log_{10}K_{\mathrm{sp,Cr(OH)}_{3}}^{*}, −3.52±0.02 for log10bCr,H*\log_{10}\beta_{\mathrm{Cr,H}}^{*}, −9.30±0.87 for log10bCr,2H*\log_{10}\beta_{\mathrm{Cr,2H}}^{*} and −17.18±0.16 for log10bCr,3H*\log_{10}\beta_{\mathrm{Cr,3H}}^{*}, respectively. All methods produced essentially the same values for the hydrolysis constants of Cr(III). 相似文献
8.
Ye Qin Wei-Feng Xue Jian-Guo Liu Wei-Guo Xu Chuan-Wei Yan Jia-Zhen Yang 《Journal of solution chemistry》2010,39(6):857-863
The molar enthalpies of solution of VOSO4⋅3.52H2O(s) at various molalities in water and in aqueous sulfuric acid (0.1 mol⋅kg−1), Δsol
H
m, were measured by a solution-reaction isoperibol calorimeter at 298.15±0.01 K. An improved Archer’s method to estimate the
standard molar enthalpy of solution, DsolH0m\Delta_{\mathrm{sol}}H^{0}_{\mathrm{m}}, was put forward. In terms of the improved method, the values of DsolH0m=-24.12±0.03 kJ·mol-1\Delta_{\mathrm{sol}}H^{0}_{\mathrm{m}}=-24.12\pm 0.03~\mbox{kJ}{\cdot}\mbox{mol}^{-1} of VOSO4⋅3.52H2O(s) in water and DsolH0m=-15.38±0.06 kJ·mol-1\Delta_{\mathrm{sol}}H^{0}_{\mathrm{m}}=-15.38\pm 0.06~\mbox{kJ}{\cdot}\mbox{mol}^{-1} in aqueous sulfuric acid were obtained, respectively. The data indicates that the energy state of VOSO4 in aqueous H2SO4 is higher than that in pure water. 相似文献
9.
Nicotinic acid (also known as niacin) was recrystallized from anhydrous ethanol. X-ray crystallography was applied to characterize its crystal structure. The crystal belongs to the monoclinic system, space group P2(1)/c. The crystal cell parameters are a = 0.71401(4) nm, b = 1.16195(7) nm, c = 0.71974(6) nm, α = 90°, β = 113.514(3)°, γ = 90° and Z = 4. Molar enthalpies of dissolution of the compound, at different molalities m/(mol·kg?1) were measured with an isoperibol solution–reaction calorimeter at T = 298.15 K. The molar enthalpy of solution at infinite dilution was calculated, according to Pitzer’s electrolyte solution model and found to be \( \Delta_{\text{sol}} H_{m}^{\infty } = ( 2 7. 3 \pm 0. 2) \) kJ·mol?1 and Pitzer’s parameters (\( \beta_{{\text{MX}}}^{{\text{(0)}L}} \), \( \beta_{{\text{MX}}}^{{\text{(1)}L}} \) and \( C_{{\text{MX}}}^{\phi L} \)) were obtained. The values of apparent relative molar enthalpies (\( {}^{\phi }L \)) and relative partial molar enthalpies (\( \overline{{L_{2} }} \) and \( \overline{{L_{1} }} \)) of the solute and the solvent at different molalities were derived from the experimental enthalpy of dissolution values of the compound. Also, the standard molar enthalpy of formation of the anion \( {\text{C}}_{ 6} {\text{H}}_{ 4} \text{NO}_{2}^{-} \) in aqueous solution was calculated to be \( {\Delta_{\text{f}}^{} H}_{\text{m}}^{\text{o}} ({\text{C}}_{ 6} {\text{H}}_{ 4} {\text{NO}}_{2}^{-} \text{,aq}) = - \left( {603.2 \pm 1.2} \right)\;{\text{kJ}}{\cdot}{\text{mol}}^{-1} \). 相似文献
10.
The stoichiometries of limiting carbonate complexes of lanthanide(III) ions were investigated by solubility measurements of
hydrated NaLn(CO3)2 solid compounds (Ln = La, Nd, Eu and Dy) at room temperature in aqueous solutions of high ionic strength (3.5 mol⋅kg−1 NaClO4) and high CO32-\mathrm{CO_{3}^{2-}} concentrations (0.1 to 1.5 mol⋅kg−1). The results were interpreted by considering the stability of carbonate complexes, with limiting species found to be La(CO3)45-\mathrm{La(CO_{3})_{4}^{5-}}, Nd(CO3)45-\mathrm{Nd(CO_{3})_{4}^{5-}}, Eu(CO3)33-\mathrm{Eu(CO_{3})_{3}^{3-}} and Dy(CO3)33-\mathrm{Dy(CO_{3})_{3}^{3-}}. TRLFS measurements on the Eu and Dy solutions confirmed the predominance of a single aqueous complex in all the samples.
Equilibrium constants were determined for the reaction Ln(CO3)33-+CO32-\mathrm{Ln(CO_{3})_{3}^{3-}}+\mathrm{CO_{3}^{2-}} ⇌ Ln(CO3)45-\mathrm{Ln(CO_{3})_{4}^{5-}}: log10K3.5m NaClO44,La=0.7±0.3\log_{10}K\mathrm{^{3.5m\:NaClO_{4}}_{4,La}=0.7\pm0.3}, log10K3.5m NaClO44,Nd=1.3±0.3\log_{10}K\mathrm{^{3.5m\:NaClO_{4}}_{4,Nd}=1.3\pm0.3}, and for Ln = Eu and Dy, log10K3.5m NaClO44,Ln £ -0.4\log_{10}K\mathrm{^{3.5m\:NaClO_{4}}_{4,Ln}\leq-0.4}. These results suggest that tetracarbonato complexes are stable only for the light lanthanide ions in up to 1.5 molal CO32-\mathrm{CO_{3}^{2-}} aqueous solutions, in agreement with our recent capillary electrophoresis study. Comparison with literature results indicates
that analogies between actinide(III) and lanthanide(III) ions of similar ionic radii do not hold in concentrated carbonate
solutions. Am(CO3)33-\mathrm{Am(CO_{3})_{3}^{3-}} was previously evidenced by solubility measurements, whereas we have observed that Nd(CO3)45-\mathrm{Nd(CO_{3})_{4}^{5-}} predominates in similar conditions. We may speculate that small chemical differences between Ln(III) and An(III) could result
in macroscopic differences when their coordination sphere is complete. 相似文献
11.
Shoichi Okouchi Pariya Thanatuksorn Shiego Ikeda Hisashi Uedaira 《Journal of solution chemistry》2011,40(5):775-785
The 17O-NMR spin-lattice relaxation times (T
1) of water molecules in aqueous solutions of n-alkylsulfonate (C1 to C6) and arylsulfonic anions were determined as a function of concentration at 298 K. Values of the dynamic hydration number,
(S-) = nh - (tc- /tc0 - 1)(\mathrm{S}^{-}) = n_{\mathrm{h}}^{ -} (\tau_{\mathrm{c}}^{-} /\tau_{\mathrm{c}}^{0} - 1), were determined from the concentration dependence of T
1. The ratios (tc -/tc0\tau_{\mathrm{c}}^{ -}/\tau_{\mathrm{c}}^{0}) of the rotational correlation times (tc -\tau_{\mathrm{c}}^{ -} ) of the water molecules around each sulfonate anion in the aqueous solutions to the rotational correlation time of pure water
(tc0\tau_{\mathrm{c}}^{0}) were obtained from the n
DHN(S−) and the hydration number (nh -n_{\mathrm{h}}^{ -} ) results, which was calculated from the water accessible surface area (ASA) of the solute molecule. The tc -/tc0\tau_{\mathrm{c}}^{ -}/\tau_{\mathrm{c}}^{0} values for alkylsulfonate anions increase with increasing ASA in the homologous-series range of C1 to C4, but then become approximately constant. This result shows that the water structures of hydrophobic hydration near large
size alkyl groups are less ordered. The rotational motions of water molecules around an aromatic group are faster than those
around an n-alkyl group with the same ASA. That is, the number of water–water hydrogen bonds in the hydration water of aromatic groups
is smaller in comparison with the hydration water of an n-alkyl group having the same ASA. Hydrophobic hydration is strongly disturbed by a sulfonate group, which acts as a water
structure breaker. The disturbance effect decreases in the following order: $\mbox{--} \mathrm{SO}_{3}^{-} > \mbox{--} \mathrm{NH}_{3}^{ +} > \mathrm{OH}> \mathrm{NH}_{2}$\mbox{--} \mathrm{SO}_{3}^{-} > \mbox{--} \mathrm{NH}_{3}^{ +} > \mathrm{OH}> \mathrm{NH}_{2}. The partial molar volumes and viscosity B
V
coefficients for alkylsulfonate anions are linearly dependent on their n
DHN(S−) values. 相似文献
12.
An electrogenerated chemiluminescence (ECL) sensor for reduced glutathione was developed based on $ \mathrm{Ru}\left( {\mathrm{bpy}} \right)_3^{2+ } $ -doped silica nanoparticles-modified gold electrode (Ru-DSNPs/Au). These uniform Ru-DSNPs (about 58?+?4 nm) were prepared by a water-in-oil microemulsion method and characterized by transmission electron microscope and scanning electron microscope. With such a unique immobilization method, a considerable $ \mathrm{Ru}\left( {\mathrm{bpy}} \right)_3^{2+ } $ was immobilized three dimensionally on the electrode, which could greatly enhance the ECL response and thus result in an increased sensitivity. The ECL analytical performances of this sensor for reduced glutathione based on the quenched ECL emission of $ \mathrm{Ru}\left( {\mathrm{bpy}} \right)_3^{2+ } $ have been investigated in detail. Under the optimum condition, the ECL intensity was linear with the reduced glutathione concentration in the range of 1.0?×?10?9 to 1.0?×?10?4?mol?L?1 (R?=?0.9971). This method has been successfully applied for the determination of reduced glutathione in serum samples with satisfactory results. The as-prepared ECL sensor for the determination of reduced glutathione displayed good sensitivity and stability. 相似文献
13.
14.
The standard molar Gibbs free energy of formation of YRhO3(s) has been determined using a solid-state electrochemical cell wherein calcia-stabilized zirconia was used as an electrolyte.
The cell can be represented by:
( - )\textPt - Rh/{ \textY2\textO\text3( \texts ) + \textYRh\textO3( \texts ) + \textRh( \texts ) }//\textCSZ//\textO2( p( \textO2 ) = 21.21 \textkPa )/\textPt - Rh( + ) \left( - \right){\text{Pt - Rh/}}\left\{ {{{\text{Y}}_2}{{\text{O}}_{\text{3}}}\left( {\text{s}} \right) + {\text{YRh}}{{\text{O}}_3}\left( {\text{s}} \right) + {\text{Rh}}\left( {\text{s}} \right)} \right\}//{\text{CSZ//}}{{\text{O}}_2}\left( {p\left( {{{\text{O}}_2}} \right) = 21.21\;{\text{kPa}}} \right)/{\text{Pt - Rh}}\left( + \right) . The electromotive force was measured in the temperature range from 920.0 to 1,197.3 K. The standard molar Gibbs energy of
the formation of YRhO3(s) from elements in their standard state using this electrochemical cell has been calculated and can be represented by:
D\textfG\texto{ \textYRh\textO3( \texts ) }/\textkJ \textmo\textl - 1( ±1.61 ) = - 1,147.4 + 0.2815 T ( \textK ) {\Delta_{\text{f}}}{G^{\text{o}}}\left\{ {{\text{YRh}}{{\text{O}}_3}\left( {\text{s}} \right)} \right\}/{\text{kJ}}\;{\text{mo}}{{\text{l}}^{ - 1}}\left( {\pm 1.61} \right) = - 1,147.4 + 0.2815\;T\;\left( {\text{K}} \right) . Standard molar heat capacity Cop,m C^{o}_{{p,m}} (T) of YRhO3(s) was measured using a heat flux-type differential scanning calorimeter in two different temperature ranges from 127 to
299 K and 305 to 646 K. The heat capacity in the higher temperature range was fitted into a polynomial expression and can
be represented by: $ {*{20}{c}} {\mathop C\nolimits_{p,m}^{\text{o}} \left( {{\text{YRh}}{{\text{O}}_3},{\text{s,}}T} \right)\left( {{\text{J}}\;{{\text{K}}^{ - 1}}{\text{mo}}{{\text{l}}^{ - 1}}} \right)} & { = 109.838 + 23.318 \times {{10}^{ - 3}}T\left( {\text{K}} \right)} & { - 12.5964 \times {{10}^5}/{T^2}\left( {\text{K}} \right).} \\ {} & {\left( {305 \leqslant T\left( {\text{K}} \right) \leqslant 646} \right)} & {} \\ $ \begin{array}{*{20}{c}} {\mathop C\nolimits_{p,m}^{\text{o}} \left( {{\text{YRh}}{{\text{O}}_3},{\text{s,}}T} \right)\left( {{\text{J}}\;{{\text{K}}^{ - 1}}{\text{mo}}{{\text{l}}^{ - 1}}} \right)} & { = 109.838 + 23.318 \times {{10}^{ - 3}}T\left( {\text{K}} \right)} & { - 12.5964 \times {{10}^5}/{T^2}\left( {\text{K}} \right).} \\ {} & {\left( {305 \leqslant T\left( {\text{K}} \right) \leqslant 646} \right)} & {} \\ \end{array} The heat capacity of YRhO3(s) was used along with the data obtained from the electrochemical cell to calculate the standard enthalpy and entropy of
formation of the compound at 298.15 K. 相似文献
15.
The oxidation of a ternary complex of chromium(III), [CrIII(DPA)(Mal)(H2O)2]?, involving dipicolinic acid (DPA) as primary ligand and malonic acid (Mal) as co-ligand, was investigated in aqueous acidic medium. The periodate oxidation kinetics of [CrIII(DPA)(Mal)(H2O)2]? to give Cr(VI) under pseudo-first-order conditions were studied at various pH, ionic strength and temperature values. The kinetic equation was found to be as follows: \( {\text{Rate}} = {{\left[ {{\text{IO}}_{4}^{ - } } \right]\left[ {{\text{Cr}}^{\text{III}} } \right]_{\text{T}} \left( {{{k_{5} K_{5} + k_{6} K_{4} K_{6} } \mathord{\left/ {\vphantom {{k_{5} K_{5} + k_{6} K_{4} K_{6} } {\left[ {{\text{H}}^{ + } } \right]}}} \right. \kern-0pt} {\left[ {{\text{H}}^{ + } } \right]}}} \right)} \mathord{\left/ {\vphantom {{\left[ {{\text{IO}}_{4}^{ - } } \right]\left[ {{\text{Cr}}^{\text{III}} } \right]_{\text{T}} \left( {{{k_{5} K_{5} + k_{6} K_{4} K_{6} } \mathord{\left/ {\vphantom {{k_{5} K_{5} + k_{6} K_{4} K_{6} } {\left[ {{\text{H}}^{ + } } \right]}}} \right. \kern-0pt} {\left[ {{\text{H}}^{ + } } \right]}}} \right)} {\left\{ {\left( {\left[ {{\text{H}}^{ + } } \right] + K_{4} } \right) + \left( {K_{5} \left[ {{\text{H}}^{ + } } \right] + K_{6} K_{4} } \right)\left[ {{\text{IO}}_{4}^{ - } } \right]} \right\}}}} \right. \kern-0pt} {\left\{ {\left( {\left[ {{\text{H}}^{ + } } \right] + K_{4} } \right) + \left( {K_{5} \left[ {{\text{H}}^{ + } } \right] + K_{6} K_{4} } \right)\left[ {{\text{IO}}_{4}^{ - } } \right]} \right\}}} \) where k 6 (3.65 × 10?3 s?1) represents the electron transfer reaction rate constant and K 4 (4.60 × 10?4 mol dm?3) represents the dissociation constant for the reaction \( \left[ {{\text{Cr}}^{\text{III}} \left( {\text{DPA}} \right)\left( {\text{Mal}} \right)\left( {{\text{H}}_{2} {\text{O}}} \right)_{2} } \right]^{ - } \rightleftharpoons \left[ {{\text{Cr}}^{\text{III}} \left( {\text{DPA}} \right)\left( {\text{Mal}} \right)\left( {{\text{H}}_{2} {\text{O}}} \right)\left( {\text{OH}} \right)} \right]^{2 - } + {\text{H}}^{ + } \) and K 5 (1.87 mol?1 dm3) and K 6 (22.83 mol?1 dm3) represent the pre-equilibrium formation constants at 30 °C and I = 0.2 mol dm?3. Hexadecyltrimethylammonium bromide (CTAB) was found to enhance the reaction rate, whereas sodium dodecyl sulfate (SDS) had no effect. The thermodynamic activation parameters were estimated, and the oxidation is proposed to proceed via an inner-sphere mechanism involving the coordination of IO4 ? to Cr(III). 相似文献
16.
U. I. Zhorszky 《Journal of mass spectrometry : JMS》1986,21(6):357-365
Bifunctional methoxonium ions \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R} -\mathop {\rm C}\limits^ + ({\rm OCH}_3 ) - ({\rm CH}_2 )_{\rm n} - {\rm OH}({\rm b}) $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R} - \mathop {\rm C}\limits^ + ({\rm OCH}_3 ) - ({\rm CH}_2 )_{\rm n} - {\rm OCH}_3 ({\rm c}) $\end{document} (c) show as the main reactions those caused by functional group interaction, as has already been found for the analogous hydroxonium ions (g). Although there are similarities in the fragmentation behaviour of the isomeric ions b and g, their fragmentation pathways are different, proving b and g as distinct species. The dominant primary fragmentation for b and c is loss of CH3OH. The hydrogen migrations prior to this reaction have been established by deuterium labelling. The findings on the fragmentation behaviour of the bifunctional methoxonium ions have been extended to the general behaviour of hydroxy and alkoxy substituted alkoxonium ions. 相似文献
17.
The oxidation of nanomolar levels of iron(II) with oxygen has been studied in NaCl solutions as a function of temperature (0 to 50?°C), ionic strength (0.7 to 5.6 mol?kg?1), pH (6 to 8) and concentration of added NaHCO3 (0 to 10 mmol?kg?1). The results have been fitted to the overall rate equation: $$\mathrm{d}\mbox{[Fe(II)]}/\mathrm{d}t=-k_{\mathrm{app}}\mbox{[Fe(II)]}[\mbox{O}_{2}]$$ The values of k app have been examined in terms of the Fe(II) complexes with OH? and CO 3 2? . The overall rate constants are given by: $$k_{\mathrm{app}}=\alpha_{\mathrm{Fe}2+}k_{\mathrm{Fe}}+\alpha_{\mathrm{Fe(OH)}+}k_{\mathrm{Fe(OH)}+}+\alpha_{\mathrm{Fe(OH)}2}k_{\mathrm{Fe(OH)}2}+\alpha_{\mathrm{Fe(CO3)}2}k_{\mathrm{Fe(CO3)}2}$$ where α i is the molar fraction and k i is the rate constant of species i. The individual rate constants for the species of Fe(II) interacting with OH? and CO 3 2? have been fitted by equations of the form: $$\begin{array}{l}\ln k_{\mathrm{Fe}2+}=21.0+0.4I^{0.5}-5562/T\\[6pt]\ln k_{\mathrm{FeOH}}=17.1+1.5I^{0.5}-2608/T\\[6pt]\ln k_{\mathrm{Fe(OH)}2}=-6.3-0.6I^{0.5}+6211/T\\[6pt]\ln k_{\mathrm{Fe(CO3)}2}=31.4+5.6I^{0.5}-6698/T\end{array}$$ These individual rate constants can be used to estimate the rates of oxidation of Fe(II) over a large range of temperatures (0 to 50?°C) in NaCl brines (I=0 to 6 mol?kg?1) with different levels of OH? and CO 3 2? . 相似文献
18.
Some equilibria involving gold(I) thiomalate (mercaptosuccinate, TM) complexes have been studied in the aqueous solution at 25 °C and I?=?0.2 mol·L?1 (NaCl). In the acidic region, the oxidation of TM by \( {\text{AuCl}}_{4}^{ - } \) proceeds with the formation of sulfinic acid, and gold(III) is reduced to gold(I). The interaction of gold(I) with TM at nTM/nAu?≤?1 leads to the formation of highly stable cyclic polymeric complexes \( {\text{Au}}_{m} \left( {\text{TM}} \right)_{m}^{*} \) with various degrees of protonation depending on pH. In general, the results agree with the tetrameric form of this complex proposed in the literature. At nTM/nAu?>?1, the processes of opening the cyclic structure, depolymerization and the formation of \( {\text{Au}}\left( {\text{TM}} \right)_{2}^{*} \) occur: \( {\text{Au}}_{4} ( {\text{TM)}}_{4}^{8 - } + {\text{TM}}^{3 - } \rightleftharpoons {\text{Au}}_{ 4} ( {\text{TM)}}_{5}^{11 - } \), log10 K45?=?10.1?±?0.5; 0.25 \( {\text{Au}}_{4} ( {\text{TM)}}_{4}^{8 - } + {\text{TM}}^{3 - } \rightleftharpoons {\text{Au(TM)}}_{2}^{5 - } \), log10 K12?=?4.9?±?0.2. The standard potential of \( {\text{Au(TM)}}_{2}^{5 - } \) is \( E_{1/0}^{ \circ } = -0. 2 5 5\pm 0.0 30{\text{ V}} \). The numerous protonation processes of complexes at pH?<?7 were described with the use of effective functions. 相似文献
19.
\( {\text{CN}} (B^{2}\Sigma ^{ + } \to X^{2}\Sigma ^{ + } ) \) violet system was investigated using optical emission spectroscopy in a non-equilibrium microwave atmospheric-pressure plasma jet in argon expanding in air. From the analysis of the emission spectra of the discharge in the range of 380 and 400 nm, the violet system of CN was found to be overlapped with the \( {\text{N}}_{2}^{ + } \left( {B^{2}\Sigma _{u}^{ + } , v = 1 \to X^{2}\Sigma _{g}^{ + } , v = 1} \right) \) and \( {\text{N}}_{2} \left( {C^{3}\Pi _{u} \to B^{3}\Pi _{g} } \right) \) bands, sequence \( \Delta \upsilon = - \;3 \). A numerical disentangle technique, developed in this work, permitted to obtain a well resolved violet system from the different systems observed, namely the nitrogen First Negative and the Second Positive systems. The \( {\text{CN}} (B^{2}\Sigma ^{ + } \to X^{2}\Sigma ^{ + } ) \) band head intensity was determined and analysed as function of discharge powers between 30 and 150 W and fluxes between 2.5 and 10.0 slm. With aid of this numerical approach it was also possible to obtain the rotational temperature, from (1600 ± 100) to (2300 ± 100) K and vibrational temperature between (9000 ± 800) and (14,000 ± 800) K along the plasma jet. The kinetics of \( {\text{CN}} (B^{2}\Sigma ^{ + } ) \) state was analysed as well. 相似文献
20.
Donald A. Palmer Pascale Bénézeth Caibin Xiao David J. Wesolowski Lawrence M. Anovitz 《Journal of solution chemistry》2011,40(4):680-702
Results of solubility experiments involving crystalline nickel oxide (bunsenite) in aqueous solutions are reported as functions
of temperature (0 to 350 °C) and pH at pressures slightly exceeding (with one exception) saturation vapor pressure. These
experiments were carried out in either flow-through reactors or a hydrogen-electrode concentration cell for mildly acidic
to near neutral pH solutions. The results were treated successfully with a thermodynamic model incorporating only the unhydrolyzed
aqueous nickel species (viz., Ni2+) and the neutrally charged hydrolyzed species (viz., Ni(OH)20)\mathrm{Ni(OH)}_{2}^{0}). The thermodynamic quantities obtained at 25 °C and infinite dilution are, with 2σ uncertainties:
log10Ks0o = (12.40 ±0.29),\varDeltarGmo = -(70. 8 ±1.7)\log_{10}K_{\mathrm{s0}}^{\mathrm{o}} = (12.40 \pm 0.29),\varDelta_{\mathrm{r}}G_{m}^{\mathrm{o}} = -(70. 8 \pm 1.7) kJ⋅mol−1;
\varDeltarHmo = -(105.6 ±1.3)\varDelta_{\mathrm{r}}H_{m}^{\mathrm{o}} = -(105.6 \pm 1.3) kJ⋅mol−1;
\varDeltarSmo = -(116.6 ±3.2)\varDelta_{\mathrm{r}}S_{m}^{\mathrm{o}} =-(116.6 \pm 3.2) J⋅K−1⋅mol−1;
\varDeltarCp,mo = (0 ±13)\varDelta_{\mathrm{r}}C_{p,m}^{\mathrm{o}} = (0 \pm 13) J⋅K−1⋅mol−1; and log10Ks2o = -(8.76 ±0.15)\log_{10}K_{\mathrm{s2}}^{\mathrm{o}} = -(8.76 \pm 0.15);
\varDeltarGmo = (50.0 ±1.7)\varDelta_{\mathrm{r}}G_{m}^{\mathrm{o}} = (50.0 \pm 1.7) kJ⋅mol−1;
\varDeltarHmo = (17.7 ±1.7)\varDelta_{\mathrm{r}}H_{m}^{\mathrm{o}} = (17.7 \pm 1.7) kJ⋅mol−1;
\varDeltarSmo = -(108±7)\varDelta_{\mathrm{r}}S_{m}^{\mathrm{o}} = -(108\pm 7) J⋅K−1⋅mol−1;
\varDeltarCp,mo = -(108 ±3)\varDelta_{\mathrm{r}}C_{p,m}^{\mathrm{o}} = -(108 \pm 3) J⋅K−1⋅mol−1. These results are internally consistent, but the latter set differs from those gleaned from previous studies recorded in
the literature. The corresponding thermodynamic quantities for the formation of Ni2+ and Ni(OH)20\mathrm{Ni(OH)}_{2}^{0} are also estimated. Moreover, the Ni(OH)3 -\mathrm{Ni(OH)}_{3}^{ -} anion was never observed, even in relatively strong basic solutions (mOH - = 0.1m_{\mathrm{OH}^{ -}} = 0.1 mol⋅kg−1), contrary to the conclusions drawn from all but one previous study. 相似文献
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