共查询到20条相似文献，搜索用时 15 毫秒
1.
The kinetics of the redox reaction between dimethylhydroxylamine (DMH) and vanadium(V) in nitric acid has been studied by spectrophotometry at 23.1 °C. The rate equation of the reaction is determined as -d[V(V)]/d t= k[V(V)][DMH] by investigating the influence of the concentrations of V(V) and DMH, acidity, ionic strength and the ratio of the initial concentrations of reactants on the redox reaction. The rate constant of the reaction k = 9.95±0.52 (mol/l) -1.s -1 when the ionic strength is 1.00 mol/l. The activation energy of the reaction is 22.1 kJ/mol. A possible mechanism of the redox reaction has been suggested on the basis of an electron spin resonance(ESR) spectrum of dimethyl nitroxyl radical, (CH 3) 2O. 相似文献
2.
We have investigated effects of shear flow on the structure of lamellar phase in hepta(oxyethylene glycol)— n—hexadecylether—water system using small-angle neutron scattering (SANS) under shear flow at the shear rates ( ) from 10 –3 s –1 to 50 s –1. In the range =10 –2 ~1 s –1, significant changes have been observed in both intensity and position of the reflection peak. Small-angle X-ray scattering without shear has been also measured at various concentrations and temperatures. It has been suggested from these results that the shear flow causes contraction of lamellar domains and formation of a new domain composed of disrupted bilayers which grows rapidly with increasing shear rate and reconstructs original microstructures.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
3.
The kinetics of oxidation-reduction reaction between N,N-diethylhydroxylamine (DEHAN) and neptunium (VI) in nitric acid media has been studied by spectrophotometry at 25.2 °C. The rate equation is -d[Np(VI)/dt= k[Np(VI)][DEHAN]/[H +] found by investigating the influence of concentration, acidity, ionic strength and temperature on the reaction. The rate constant of the reaction k is 23.0±1.8 min –1 for = 2.0 mol/l. A possible mechanism of reaction has been suggested according to the ESR spectra of nitroxide radical produced in the DEHAN+V(V) system. 相似文献
4.
The power-time curves of two species of bacteria, Vibro metschnikovii, Vibro bollisae were determined calorimetrically by using a 2277 bioactivity monitor. The power-time curve equation of bacterial growth in the log phase can be expressed as . A self-function recursion equation, fi=b 1fi+1+b 2fi+2, was obtained through the perfect non-linear function . A linear equation, i/ i+1= b1+ b2i+2/ i+1, was obtained by using the self-function recursion equation. The rate constants of bacterial growth k1, the time constant of the calorimeter k, the generation times G, and the pre-exponential factors A were obtained from the power—time curve equations.Power—time curve equations of bacterial growth in the log phase are expressed for V.metschnikovii as =1.05(e 0.0228t–e –0.0175t), and for V. bollisae as =1.58(e 0.0278t–e –0.0170t).This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
5.
The solubility of siderite (FeCO 3) at 25°C under constant CO 2 partial pressure [ p(CO 2)] was determined in NaCl solutions as a function of ionic strength. The dissolution of FeCO 3(s) for the reaction has been determined as a function of pH = – log[H +]. From these values we have determined the equilibrium constant for the stoichiometric solubility to FeCO 3(s) in NaCl These values have been fitted to the equation with a standard error of s = 0.15. The extrapolated value of log( K
o
sp) – 10.9 in water is in good agreement with data in the literature (– 10.8 to – 11.2) determined in solutions of different composition and ionic strength.The measured values of the activity coefficient, T(Fe 2+) T(CO 3
2–), have been used to estimate the stability constant for the formation of the FeCO 3 ion pair, K*(FeCO 3). The values of K*(FeCO 3) have been fitted to the equation ( s = 0.09) The value of log[ K
o(FeCO 3)] in water found in this study (6.3 ± 0.2) is slightly higher than the value found from extrapolations in 1.0 m NaClO 4 solutions (5.9 ± 0.2). These differences are related to the model used to determine the activity coefficients of the Fe(II) and carbonate species in the two solutions. 相似文献
6.
The kinetics of the reaction of manganese(III) with oxalic acid (OA) has been studied in H 2SO 4 solutions. Under the experimental conditions of 6 × 10 –3 <> 0 < 0.4=" mol="> –3 and [H 2SO 4] 0 0.2 mol dm –3 the observed pseudo-first order rate constant k
obs follows the expression |
相似文献
7.
The kinetics of the oxidation-reduction reaction between N,N-diethylhydroxylamine (DEHAN) and vanadium(V) in nitric acid media have been studied by spectrophotometry at 13.5 °C. The rate equation of reaction was found to be -d[V(V)]/d t = k [V(V)] [DEHAN] by investigating the influence of the concentration, acidity, ionic strength and the effect of initial concentration on reaction. The rate constant of reaction k = 36.38 mol/l -2 ·min -1 when = 2.0 mol/l. A possible mechanism of reaction has been suggested on the basis of chemical analysis, 1 H NMR and ESR spectra. 相似文献
8.
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
9.
The kinetics and mechanism of chromium(VI) oxidation of L-methionine in acidic medium have been studied spectrophotometrically. The reaction proceeds via the formation of a transient intermediate ( max = 410–420 nm) which decomposes by a proton catalyzed pathway. The rate law is: The activation enthalpy and activation entropy for the reaction have been calculated to be H
* = 43.85 kJ mol –1, S
* = –286.87 JK –1 mol –1. Also values of k
1, k
–1 and k
3 were determined: 27.2 × 10 –3 M –1 S –1, 1.97 × 10 –3 S –1, 7.2 × 10 –3 s –1, respectively. The results are compared with those of related studies for reduction of chromate by amino acids. 相似文献
10.
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
11.
In this work some calorimetric measurements were also carried out on the electrorefining silver by using different current densities with a Calvet type microcalorimeter at room temperature. The ratio ( R) of the measured heat ( m) to the input electric energy ( in) and the excess heat ( ex), i.e., difference between m and in during the electrorefining process, were discussed in terms of general thermodynamics. It was found that the R and ex for silver were related with the current density or cell voltage employed in the experiment. The results obtained here also indicate that the heat generation under different conditions, such as different currents or voltages may be caused partially by the irreversibility of the process or by some unknown processes.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
12.
Conditional stability constants of 2-[ bis(2-hydroxyethyl)amino]-2(hydroxymethyl)-1,3-propanediol (BT) complexes of trivalent rare earth element (Ln) ions (La, Nd, Eu, Gd, Yb, Dy, Er, Lu) and Y were determined potentiometrically in aqueous NaCl solutions at 30°C and 0.1 M ionic strength. Least-squares fitting shows that, at <0.04 molal BT, the complex LnBT 3+ is dominant, with LnBT 2
3+ forming a secondary complex, where: Conditional stability constants appear to be directly related to the ionic radius of the trivalent ion in question. The optimal ionic radius, 104–105 pm, yields values of log
(Gd) and
(Yb). Complexation drops off steeply on either side of the ideal ionic radius. In relating the stability constants to ionic radius, it is assumed that BT complexes with Gd, Dy, Er, and Lu have coordination number eight, whereas those with La, Nd, and Eu have coordination number nine. The smoothest trend of stability constants with ionic radius is obtained if Yb–BT complexes are assumed to have coordination number nine. These results may reflect the ability of BT to form an ionic radius-specific chelate structure. 相似文献
13.
The solubility of rhodochrosite (MnCO 3) at 25°C under constant carbon dioxide partial pressure p(CO 2) was determined in NaCl solutions as a function of ionic strength I. The dissolution of MnCO 3(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 MnCO 3(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(Mn 2+) and T(CO 3
2–), have been used to estimate the stability constant for the formation of the MnCO 3ion pair, K
*(MnCO 3
0). The value of K
0(MnCO 3
0) calculated from the values of K
*(MnCO 3) by the Pitzer equation ( = 0.1) in this study (4.8 ± 0.1) is in reasonable agreement with literature data. 相似文献
14.
The kinetics of the first order autocatalytic decomposition reaction of highly nitrated nitrocellulose (HNNC, 14.14%N) was studied by using thermogravimetry (TG). The results show that the TG curve for the initial 50% of mass-loss of HNNC can be described by the first order autocatalytic equation and that for the latter 50% mass-loss of HNNC described by the reaction equations
and This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
15.
The kinetics of the reactions of ClO 3
− with HSO 3
− and H 2SO 3 was studied by measuring the concentration of [Cl −] and [H +] both in chlorate-bisulfite and chlorate-sulfite/bisulfite solutions. A reaction mechanism was applied for simulation of
the experimental observations. Rate constants k 1 = (1±0.5)·10 −4 M −1 s −1 and k 2 = (0.23±0.01) M −1 s −1 were determined for the following reactions:
Rate constant k 1 was obtained directly from the experimental results of chloratesulfite/ bisulfite reactions, where reaction (1) is predominant.
Rate constant k 2 was obtained by computer fitting of [Cl −] and [H +] to the experimental values both in chlorate-bisulfite and chlorate-sulfite/bisulfite reactions. 相似文献
16.
Crystalline gallosilicates with a pentasil (MFI) framework containing Ga 3+ in lattice positions were synthesised. The kinetic features of the hydrothermal system containing triethyl- n-butylammonium cations (TEBA) + as template in the gel system have been investigated. The gallosilicate products were characterized by XRD, framework-IR, TG/DTA, 29Si and 71Ga MASNMR and sorption measurements using standard techniques. |
相似文献
17.
The theory of the polarographic catalytic currents (mechanism CE) has been developed for the system: Ni 2+-L-X p− where L: pyridine (Py), nicotinamide (NA), N, N-diethylnicotinamide (DEN), nicotine (NC) and X p−: NO −
3, AcO −, HPO 2−
4 . The theory is based on the kinetic parallel heterogeneous catalytic reactions:
with the use of Langmuir’s adsorbed isotherm. The kinetic equations obtained for average and instantaneous currents allowed
to determine the Langmuir’s parameters (NA<DEN<NC), kinetic parameters and the contribution of reactions 1a and b to the summary catalytic currents. The k
h″ value rises with the increase of the NiX 2−p stability constant. The correlation k
h″≫ k
h′ was explained by the additional effect of the field electrode through X p−. These effects base the reaction 1b instead of accepted early alternative reaction of the ligand exchange. In spite of the fact that k
h″≫ k
h′, the contribution of the reaction 1a in the summary catalytic current attained more than 60% (Py, DEN) due to the influence of the ψ 0 potential.
Dedicated to Professor Zbigniew Galus on the occasion of his 70th birthday and in recognition of his many contributions to
electrochemistry 相似文献
18.
The equilibrium constant for the hydrolytic disproportionation of I 2
has been determined at 25°C and at ionic strength 0.2 M(NaClO 4) in buffered solution. The reaction was followed in the pH range where the equilibrium concentration of I 2, I –, and IO 3
–are commensurable, i.e., the fast equilibrium is also established. The equilibrium concentrations of I 2and I 3
–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
19.
The kinetics of oxidation of N-methyl- p-aminophenol (metol) by H 2O 2 in the presence of trace levels of Fe III have been studied in an HClO 4 medium. The reaction mechanism is complex and the catalytic role of Fe III in the sulphato form is indicated. The following rate law accounts for the experimental observations: |
相似文献
20.
The density and compressibility of seawater salt solutions for ionic strengths 0to 0.8 m, temperatures 0–40°C, and applied pressure 0 to 1000 barare fitted tothe Pitzer equations. The apparent molal volumes and compressibilities ( X) arefitted to equations of the form where I is the ionic strength, m is the molality of seasalt, A
X is the Debye—Hückelslope for the volume ( X = V) or compressibility( X = ) and g( y) = (2/ y
2)[1 – (1 + y)exp( x)] where y = 2 I
0.5. The Pitzer parameters (0)X, (1)X, and C
Xare fitted to functions of temperature and pressure in the form where a
ij are adjustable parameters, Y
X is the Pitzer parameter, T is the temperaturein K, T
R = 298.15 K, and P is the applied pressure in bars ( P = 0 at 1 atm or1.013 bar). The standard deviations of the seawater fits are 8.3×10 –6 cm 3-g –1for the specific volumes, 0.0007×10 –6 bar –1 for the compressibilities, and0.63×10 –6 K –1 for the thermal expansibilities. At 25°C, the measured densitiesof seawater are compared to the calculated values using Pitzer coefficients forthe major sea salts. The results agree with the measured values to within 45×10 –6g-cm –3. 相似文献
|
|
|
|
|
