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1.
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
2.
The decomposition of hydrogen peroxide in the presence of hydroxonitrilotri(methylenephosphonato)iron(III), [Fe(NTMP)(OH) 4–], was studied in nitrate media (=0.10–0.26 M) over the 0.2–0.5 mM concentration range for the iron complex and the temperature range 26–40°C. The rate law; |
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3.
The kinetics of the silylation of hydroxylated silica, the non-porous Aerosil using trimethylchlorosilane, under various reaction conditions has been investigated by a gravimetric technique and found to follow the law: |
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4.
A new approximation has been proposed for calculation of the general temperature integral $
\int\limits_0^T {T^m } e^{ - E/RT} dT
$
\int\limits_0^T {T^m } e^{ - E/RT} dT
, which frequently occurs in the nonisothermal kinetic analysis with the dependence of the frequency factor on the temperature
( A= A
0
T
m). It is in the following form:
|
$
\int\limits_0^T {T^m } e^{ - E/RT} dT = \frac{{RT^{m + 2} }}
{E}e^{ - E/RT} \frac{{0.99954E + (0.044967m + 0.58058)RT}}
{{E + (0.94057m + 2.5400)RT}}
$
\int\limits_0^T {T^m } e^{ - E/RT} dT = \frac{{RT^{m + 2} }}
{E}e^{ - E/RT} \frac{{0.99954E + (0.044967m + 0.58058)RT}}
{{E + (0.94057m + 2.5400)RT}}
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5.
The kinetics of oxidation of the chromium(III)-DL- aspartic acid complex, [CrIIIHL]+ by periodate have been investigated in aqueous medium. In the presence of Fe II as a catalyst, the following rate law is obeyed: Catalysis is believed to be due to the oxidation of iron(II) to iron(III), which acts as the oxidizing agent. Thermodynamic activation parameters were calculated. It is proposed that electron transfer proceeds through an inner-sphere mechanism via coordination of IO
4
-
to Cr III. 相似文献
6.
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
7.
Enthalpic relaxation has been used to model the development of the glass transition in polymers, using kinetic parameters
determined separately. For this purpose the Kohlrausch-Williams-Watt stretched exponential function, relating the extent of
relaxation, Φ(t), to time t and an average relaxation time, τ a, i.e. where β is inversely related to the breadth of the relaxation spectrum, has been adopted. The relaxation time dependence
on temperature was taken to follow the modified Arrhenius relationship, where T is the storage and T′ the fictive temperature, X is the structure factor and ΔH the activation enthalpy. Both have
been found to describe the process of enthalpic relaxation in polymer glasses and a direct comparison has been made with the
change in specific heat observed with different cooling rates in DSC experiments. The effect of variables, such as activation
enthalpies, pre-exponential factors, and the non-linear factors such as X and β on the observed T gs and the temperature range over which the transition occurred have been determined.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
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 ZrO 2-x(OH) 2xyH 2O where x2 and 1 y<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
9.
Alkaline hexacyanoferrate(III) oxidation of freshly prepared solutions of Cr III (pH>12) at 27°C follows the rate law, Equation 1: |
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10.
The oxidation of H 2NOH is first-order both in [NH 3OH +] and [AuCl 4
–]. The rate is increased by the increase in [Cl –] and decreased with increase in [H +]. The stoichiometry ratio, [NH 3OH +]/[AuCl 4
–], 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
11.
The Gibbs free energies of formation of Eu 3RuO 7(s) and Eu 2Ru 2O 7(s) have been determined using solid-state electrochemical technique employing oxide ion conducting electrolyte. The reversible electromotive force (e.m.f.) of the following solid-state electrochemical cells have been measured:
The Gibbs free energies of formation of Eu 3RuO 7(s) and Eu 2Ru 2O 7(s) from elements in their standard state, calculated by the least squares regression analysis of the data obtained in the present study, can be given, respectively, by:
The uncertainty estimates for Δ f
G
o( T) include the standard deviation in e.m.f. and uncertainty in the data taken from the literature. 相似文献
12.
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 p K
2 on dielectric constant of the mixed solvents is discussed in term of the Beveridge model. 相似文献
13.
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
14.
In the search of a useful
method for determining excess enthalpies as a function of temperature Calvet
calorimetry was employed. To this end, excess molar enthalpies at 298.15 and 333.15 K and excess molar heat capacities within 283.15–333.15 K were
determined for the 1-decanol+ n-decane system
over the whole composition range. An isothermal flow Calvet-type calorimeter
was used for measurements, whereas were determined by means of a Setaram
Micro DSC calorimeter. Excess enthalpies within 283.15–333.15 K were
indirectly obtained through the integration of ( T) data using at 298.15 K. The results obtained at 333.15 K agreed with those
determined directly, implying the thermodynamic consistency of the measured
data and, therefore, the reliability of the indirect method. 相似文献
15.
The osmium(VIII) catalysed IO 4
− oxidation of DMF in aqueous alkaline medium follows the rate law:
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16.
Activity coefficients for sodium chloride in the NaCl + Na 2SO 4 + H 2O 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
17.
The kinetics of aqua ligand substitution from cis-[Ru(bipy) 2(H 2O) 2] 2+ by 1, 10-phenanthroline (phen) have been studied spectrophotometrically in the 35 to 50°C temperature range. We propose the following rate law for the reaction within the 3.65 to 5.5 pH range: |
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18.
It is shown that the total differential of the function of the amount of conversion versus temperature and time ( =f(T, t)) is equal to zero non-isothermal kinetics at constant heating rate. Hence, the mathematical expression used in the literature for the rate of the non-isothermal transformation,
, is not valid. 相似文献
19.
The example of the sequence of reactions and the steady-state approximation are used to present a demonstration of the fact that the evolution of the reaction rates
under non-isothermal conditions depends on the ratio of the activation energies and on the heating rate. At the same time,
it is shown that, under isothermal conditions, the ratio of the activation energies plays no role.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
Zusammenfassung Es wird das quantenmechanische Problem eines Teilchens in einem ringförmigen Potential der Art
gelöst.
The motion of a body in a ring-shaped potential The quantum mechanical problem of a particle in the torus shaped potential
is solved.
Résumé Solution du problème quantique de la particule dans un potentiel toroïdal:
.
Dem Andenken an meinen Freund Karl Heinz Hansen gewidmet. 相似文献
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