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1.
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
2.
As a new method, stable-isotope dilution activation analysis has been developed. When an element consists of at least two stable isotopes which are converted easily to the radioactive nuclides through nuclear reactions, the total amount of the element (xg) can be determined by irradiating simultaneously the duplicated sample containing small amounts of either enriched isotope (y g), and by using the following equation. $${{x = y\left( {{M \mathord{\left/ {\vphantom {M {M*}}} \right. \kern-\nulldelimiterspace} {M*}}} \right)\left[ {\left( {{{R*} \mathord{\left/ {\vphantom {{R*} R}} \right. \kern-\nulldelimiterspace} R}} \right)\left( {{{\theta _2^* } \mathord{\left/ {\vphantom {{\theta _2^* } {\theta _2 }}} \right. \kern-\nulldelimiterspace} {\theta _2 }}} \right) - \left( {{{\theta _1^* } \mathord{\left/ {\vphantom {{\theta _1^* } {\theta _1 }}} \right. \kern-\nulldelimiterspace} {\theta _1 }}} \right)} \right]} \mathord{\left/ {\vphantom {{x = y\left( {{M \mathord{\left/ {\vphantom {M {M*}}} \right. \kern-\nulldelimiterspace} {M*}}} \right)\left[ {\left( {{{R*} \mathord{\left/ {\vphantom {{R*} R}} \right. \kern-\nulldelimiterspace} R}} \right)\left( {{{\theta _2^* } \mathord{\left/ {\vphantom {{\theta _2^* } {\theta _2 }}} \right. \kern-\nulldelimiterspace} {\theta _2 }}} \right) - \left( {{{\theta _1^* } \mathord{\left/ {\vphantom {{\theta _1^* } {\theta _1 }}} \right. \kern-\nulldelimiterspace} {\theta _1 }}} \right)} \right]} {\left[ {1 - \left( {{{R*} \mathord{\left/ {\vphantom {{R*} R}} \right. \kern-\nulldelimiterspace} R}} \right)} \right]}}} \right. \kern-\nulldelimiterspace} {\left[ {1 - \left( {{{R*} \mathord{\left/ {\vphantom {{R*} R}} \right. \kern-\nulldelimiterspace} R}} \right)} \right]}}$$ Where M and M* are atomic weights of the element to be determined and the enriched isotope used as a spike,θ 1 andθ 2 are natural abundances of two stable isotopes in the element,θ 1 * andθ 2 * are isotopic compositions of the above isotopes in the enriched isotope, and R and R* are counting ratios of gamma-rays emitted by two radionuclides produced in the sample and the isotopic mixture. Neither calibration standard nor correction of irradiation conditions are necessary for this method. Usefulness of the present method was verified by photon activations of Ca, Zn and Ce using isotopically enriched48ca,68Zn and142Ce. 相似文献
3.
Summary The oxidation of H2O2 by [W(CN)8]3– has been studied in aqueous media between pH 7.87 and 12.10 using both conventional and stopped-flow spectrophotometry. The reaction proceeds without generation of free radicals. The experimental overall rate law,
, strongly suggests two types of mechanisms. The first pathway, characterized by the pH-dependent rate constant k
s, given by
, involves the formation of [W(CN)8· H2O2]3–, [W(CN)8· H2O2·W(CN)8]6– and [W(CN)8· HO]3– intermediates in rapid pre-equilibria steps, and is followed by a one-electron transfer step involving [W(CN)8·HO]3– (k
a) and its conjugate base [W(CN)8·O]4– (k
b). At 25 °C, I = 0.20 m (NaCl), the rate constant
with H
a
=40±6kJmol–1 and S
a
=–151±22JK–1mol–1; the rate constant
with H
b
=36±1kJmol–1 and S
b
=–136±2JK–1mol–1 at 25 °C, I = 0.20 m (NaCl); the acid dissociation constant of [W(CN)8·HO]3–, K
5
=(5.9±1.7)×10–10
m, with
and
is the first acid dissociation constant of H2O2. The second pathway, with rate constant, k
f, involves the formation of [W(CN)8· HO2]4– and is followed by a formal two-electron redox process with [W(CN)8]3–. The pH-dependent rate constant, k
f, is given by
. The rate constant k
7
=23±6m
–1
s
–1 with
and
at 25°C, I = 0.20 m (NaCl). 相似文献
4.
Toshiyuki Abe Keiji Nagai Takeshi Matsukawa Akio Tajiri Takayoshi Norimatsu 《Journal of Solid State Electrochemistry》2007,11(2):303-309
We have recently reported that the organic bilayer of 3,4,9,10-perylenetetracarboxyl-bisbenzimidazole (PTCBI, n-type semiconductor) and 29H,31H-phthalocyanine (H2Pc, p-type semiconductor), which is a part of a photovoltaic cell, acts as a photoanode in the water phase (Abe et al., ChemPhysChem 5:716, [2004]); in that case, the generation of the photocurrent involving an irreversible thiol oxidation at the H2Pc/water interface took place to be coupled with hole conduction through the H2Pc layer, based on the photophysical character of the bilayer. In the present work, the photoelectrode characteristics of the bilayer were investigated in the water phase containing a redox molecule , where the photo-induced oxidation and reduction for the couple were found to take place at the bilayer. The photoanodic current involving the oxidation efficiently occurred at the interface of H2Pc/water, similar to the previous example. In the view of the voltammograms obtained, it was noted that there are pin-holes in the H2Pc layer of the bilayer, leading to a cathodic reaction with at the PTCBI surface especially in the dark; that is, the band bending at the PTCBI/water interface can essentially be reduced by applying a negative potential [e.g., < ∼ 0 V (vs Ag/AgCl)] to the PTCBI, when the cathodic reaction may take place through the conduction band of the PTCBI. Moreover, under that applied potential condition of irradiation, the photogenerated electron carrier part can move to the PTCBI surface, thus enhancing the reduction of . 相似文献
5.
Doz. Dr. Maria Pryszczewska 《Monatshefte für Chemie / Chemical Monthly》1974,105(4):726-734
Quantitative studies of the rate of Cu2S-formation by thioacetamide (TAA) were made with the help of the polarographic method of continuous registration at constant potential, and the following equation for the reaction rate between Cu+-ions andTAA in ammoniacal solutions was derived: 1 $$ - \frac{{d[Cu^I ]}}{{dt}} = k \cdot \frac{{[Cu^I ] \cdot [CH_3 CSNH_2 ]}}{{[NH_3 H_2 O]^{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{$2$}}} \cdot [H^ + ]}}\frac{{^{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 4}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{$4$}}} }}{{^{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 {10}}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{${10}$}}} }} \cdot \frac{{f_{Cu} }}{{f_{H^{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 {10}}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{${10}$}}} } }}$$ The value at 25.0° of the rate constantk is (1.6±0.2)·10?2 mole7/20·litre?7/20·sec?1. The validity of equation (1) has been proved over the pH range 8.5–9.5 and the ammonia concentration of 4.0·10?2–4.0·10?1 mole per litre, by only a small excess ofTAA and moderate reaction rates. 相似文献
6.
Reinaldo F. Teófilo Helder J. Ceragioli Alfredo C. Peterlevitz Leonardo M. Da Silva Flavio S. Damos Márcia M. C. Ferreira Vitor Baranauskas Lauro T. Kubota 《Journal of Solid State Electrochemistry》2007,11(10):1449-1457
The electrochemical properties of boron-doped diamond (BDD) polycrystalline films grown on tungsten wire substrates using
ethanol as a precursor are described. The results obtained show that the use of ethanol improves the electrochemistry properties
of “as-grown” BDD, as it minimizes the graphitic phase upon the surface of BDD, during the growth process. The BDD electrodes
were characterized by Raman spectroscopy, scanning electronic microscopy, cyclic voltammetry (CV), and electrochemical impedance
spectroscopy (EIS). The boron-doping levels of the films were estimated to be ∼1020 B/cm3. The electrochemical behavior was evaluated using the and redox couples and dopamine. Apparent heterogeneous electro-transfer rate constants were determined for these redox systems using the CV and EIS techniques. values in the range of 0.01–0.1 cm s−1 were observed for the and redox couples, while in the special case of dopamine, a lower value of 10−5 cm s−1 was found. The obtained results showed that the use of CH3CH2OH (ethanol) as a carbon source constitutes a promising alternative for manufacturing BDD electrodes for electroanalytical
applications. 相似文献
7.
The quantitative study of the equilibrium Pu4++Cl−⇋Pu3++1/2 Cl2 in LiCl−KCl (70–30% mol) at 455, 500, 550 and 600°C by visible and near I.R. absorption spectrophotometry allows the calculation
of the reaction's equilibrium constant, the mean thermodynamic data ΔH=27±14 kJ·mol−1 and ΔS=37±17 J·mol−1·K−1 and the standard potential of the couple
.
相似文献
8.
The oxidation of aquaethylenediaminetetraacetatocobaltate(II) [Co(EDTA)(H2O)]−2 by N-bromosuccinimide (NBS) in aqueous solution has been studied spectrophotometrically over the pH 6.10–7.02 range at 25 °C.
The reaction is first-order with respect to complex and the oxidant, and it obeys the following rate law:
\textRate = k\textet K 2 K 3 [ \textCo\textII ( \textEDTA )( \textH 2 \textO ) - 2 ]\textT [\textNBS] \mathord | / |
\vphantom [\textNBS] ( [ \textH + ] + K 2 ) ( [ \textH + ] + K 2 ) {\text{Rate}} = k^{\text{et} } K_{ 2} K_{ 3} \left[ {{\text{Co}}^{\text{II}} \left( {\text{EDTA}} \right)\left( {{\text{H}}_{ 2} {\text{O}}} \right)^{ - 2} } \right]_{\text{T}} {{[{\text{NBS}}]} \mathord{\left/ {\vphantom {{[{\text{NBS}}]} {\left( {\left[ {{\text{H}}^{ + } } \right]{ + }K_{ 2} } \right)}}} \right. \kern-\nulldelimiterspace} {\left( {\left[ {{\text{H}}^{ + } } \right]{ + }K_{ 2} } \right)}} 相似文献
9.
The Gibbs free energies of formation of Eu3RuO7(s) and Eu2Ru2O7(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:
10.
Oxidation of 3-(4-methoxyphenoxy)-1,2-propanediol (MPPD) by bis(hydrogenperiodato) argentate(III) complex anion, [Ag(HIO6)2]5− has been studied in aqueous alkaline medium by use of conventional spectrophotometry. The major oxidation product of MPPD
has been identified as 3-(4-methoxyphenoxy)-2-ketone-1-propanol by mass spectrometry. The reaction shows overall second-order
kinetics, being first-order in both [Ag(III)] and [MPPD]. The effects of [OH−] and periodate concentration on the observed second-order rate constants k′ have been analyzed, and accordingly an empirical expression has been deduced:
11.
Potentiometric method was used to measure the redox potentials of Tm3+/Tm2+ in a eutectic melt of sodium, potassium, and cesium chlorides relative to a chlorine reference electrode in the temperature
range 823–973 K. The main thermodynamic characteristics of the redox reaction TmCl2(solution) + 1/2Cl2(g) ⇆ TmCl3(solution) were calculate from the conditional standard potentials $
E_{{{Tm^{3 + } } \mathord{\left/
{\vphantom {{Tm^{3 + } } {Tm^{2 + } }}} \right.
\kern-\nulldelimiterspace} {Tm^{2 + } }}}^*
$
E_{{{Tm^{3 + } } \mathord{\left/
{\vphantom {{Tm^{3 + } } {Tm^{2 + } }}} \right.
\kern-\nulldelimiterspace} {Tm^{2 + } }}}^*
. 相似文献
12.
R. Pankajavalli Ashish Jain R. Babu S. Anthonysamy K. Ananthasivan V. Ganesan K. Nagarajan 《Journal of Thermal Analysis and Calorimetry》2013,111(2):1609-1614
The standard Gibbs energy of formation of Pr2TeO6 $ (\Updelta_{\text{f}} G^{^\circ } \left( {{ \Pr }_{ 2} {\text{TeO}}_{ 6} ,\;{\text{s}}} \right)) $ was derived from its vapour pressure in the temperature range of 1,400–1,480 K. The vapour pressure of TeO2 (g) was measured by employing a thermogravimetry-based transpiration method. The temperature dependence of the vapour pressure of TeO2 over the mixture Pr2TeO6 (s) + Pr2O3 (s) generated by the incongruent vapourization reaction, Pr2TeO6 (s) = Pr2O3 (s) + TeO2 (g) + ½ O2 (g) could be represented as: $ { \log }\left\{ {{{p\left( {{\text{TeO}}_{ 2} ,\;{\text{g}}} \right)} \mathord{\left/ {\vphantom {{p\left( {{\text{TeO}}_{ 2} ,\;{\text{g}}} \right)} {{\text{Pa}} \pm 0.0 4}}} \right. \kern-0em} {{\text{Pa}} \pm 0.0 4}}} \right\} = 19. 12- 27132\; \left({\rm{{{\text{K}}}}/T} \right) $ . The $ \Updelta_{\text{f}} G^{^\circ } \;\left( {{ \Pr }_{ 2} {\text{TeO}}_{ 6} } \right) $ could be represented by the relation $ \left\{ {{{\Updelta_{\text{f}} G^{^\circ } \left( {{ \Pr }_{ 2} {\text{TeO}}_{ 6} ,\;{\text{s}}} \right)} \mathord{\left/ {\vphantom {{\Updelta_{\text{f}} G^{^\circ } \left( {{ \Pr }_{ 2} {\text{TeO}}_{ 6} ,\;{\text{s}}} \right)} {\left( {{\text{kJ}}\,{\text{mol}}^{ - 1} } \right)}}} \right. \kern-0em} {\left( {{\text{kJ}}\,{\text{mol}}^{ - 1} } \right)}} \pm 5.0} \right\} = - 2 4 1 5. 1+ 0. 5 7 9 3\;\left(T/{\text{K}}\right) .$ Enthalpy increments of Pr2TeO6 were measured by drop calorimetry in the temperature range of 573–1,273 K and heat capacity, entropy and Gibbs energy functions were derived. The $ \Updelta_{\text{f}} H_{{298\;{\text{K}}}}^{^\circ } \;\left( {{ \Pr }_{ 2} {\text{TeO}}_{ 6} } \right) $ was found to be $ {{ - 2, 40 7. 8 \pm 2.0} \mathord{\left/ {\vphantom {{ - 2, 40 7. 8 \pm 2.0} {\left( {{\text{kJ}}\,{\text{mol}}^{ - 1} } \right)}}} \right. \kern-0em} {\left( {{\text{kJ}}\,{\text{mol}}^{ - 1} } \right)}} $ . 相似文献
13.
The steady-state viscosity η, the dynamic viscosity η′, and the storage modulus G′ of several high-density and low-density polyethylene melts were investigated by using the Instron rheometer and the Weissenberg rheogoniometer. The theoretical relation between the two viscosities as proposed earlier is:\documentclass{article}\pagestyle{empty}\begin{document}$ \eta \left( {\dot \gamma } \right){\rm } = {\rm }\int {H\left( {\ln {\rm }\tau } \right)} {\rm }h\left( \theta \right)g\left( \theta \right)^{{\raise0.7ex\hbox{$3$} \!\mathord{\left/ {\vphantom {3 2}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{$2$}}} \tau {\rm }d{\rm }\ln {\rm }\tau $\end{document}, where \documentclass{article}\pagestyle{empty}\begin{document}$ \theta {\rm } = {\rm }{{\dot \gamma \tau } \mathord{\left/ {\vphantom {{\dot \gamma \tau } 2}} \right. \kern-\nulldelimiterspace} 2} $\end{document}; \documentclass{article}\pagestyle{empty}\begin{document}$ {\dot \gamma } $\end{document} is the shear rate, H is the relaxation spectrum, τ is the relaxation time, \documentclass{article}\pagestyle{empty}\begin{document}$ g\left( \theta \right){\rm } = {\rm }\left( {{2 \mathord{\left/ {\vphantom {2 \pi }} \right. \kern-\nulldelimiterspace} \pi }} \right)\left[ {\cot ^{ - 1} \theta {\rm } + {\rm }{\theta \mathord{\left/ {\vphantom {\theta {\left( {1 + \theta ^2 } \right)}}} \right. \kern-\nulldelimiterspace} {\left( {1 + \theta ^2 } \right)}}} \right] $\end{document}, and \documentclass{article}\pagestyle{empty}\begin{document}$ h\left( \theta \right){\rm } = {\rm }\left( {{2 \mathord{\left/ {\vphantom {2 \pi }} \right. \kern-\nulldelimiterspace} \pi }} \right)\left[ {\cot ^{ - 1} \theta {\rm } + {\rm }{{\theta \left( {1{\rm } - {\rm }\theta ^2 } \right)} \mathord{\left/ {\vphantom {{\theta \left( {1{\rm } - {\rm }\theta ^2 } \right)} {\left( {1{\rm } + {\rm }\theta ^2 } \right)^2 }}} \right. \kern-\nulldelimiterspace} {\left( {1{\rm } + {\rm }\theta ^2 } \right)^2 }}} \right] $\end{document}. Good agreement between the experimental and calculated values was obtained, without any coordinate shift, for high-density polyethylenes as well as for a low density sample with low nw, the weight-average number of branch points per molecule. The correlation, however, was poor with low-density samples with large values of the long-chain branching index nw. This lack of coordination can be related to nw. The empirical relation of Cox and Merz failed in a similar way. 相似文献
14.
Emil N. Rizkalla M. Abd-Elkhalek Mansour Samy S. Anis 《Transition Metal Chemistry》1989,14(2):131-134
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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