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1.
The standard molar Gibbs free energy of formation of YRhO 3(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:
( - )\text Pt - Rh/{ \text Y2\text O\text3( \text s ) + \text YRh\text O3( \text s ) + \text Rh( \text s ) }//\text CSZ//\text O2( p( \text O2 ) = 21.21 \text kPa )/\text Pt - 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 YRhO 3(s) from elements in their standard state using this electrochemical cell has been calculated and can be represented by:
D \textfG\texto{ \text YRh\text O3( \text s ) }/\text kJ \text mo\text l - 1( ±1.61 ) = - 1,147.4 + 0.2815 T ( \text K ) {\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 YRhO 3(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 YRhO 3(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
2.
Combustion calorimetry, Calvet-drop sublimation calorimetry, and the Knudsen effusion method were used to determine the standard
( p
o = 0.1 MPa) molar enthalpies of formation of monoclinic (form I) and gaseous paracetamol, at T = 298.15 K:
\Updelta \textf H\textm\texto ( \text C 8 \text H 9 \text O 2 \text N,\text cr I ) = - ( 4 10.4 ±1. 3)\text kJ \text mol - 1 \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ cr I}}} \right) = - ( 4 10.4 \pm 1. 3){\text{ kJ}}\;{\text{mol}}^{ - 1} and
\Updelta \textf H\textm\texto ( \text C 8 \text H 9 \text O 2 \text N,\text g ) = - ( 2 80.5 ±1. 9)\text kJ \text mol - 1 . \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ g}}} \right) = - ( 2 80.5 \pm 1. 9){\text{ kJ}}\;{\text{mol}}^{ - 1} . From the obtained
\Updelta \textf H\textm\texto ( \text C 8 \text H 9 \text O 2 \text N,\text cr I ) \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ cr I}}} \right) value and published data, it was also possible to derive the standard molar enthalpies of formation of the two other known
polymorphs of paracetamol (forms II and III), at 298.15 K:
\Updelta \textf H\textm\texto ( \text C 8 \text H 9 \text O 2 \text N,\text crII ) = - ( 40 8.4 ±1. 3)\text kJ \text mol - 1 \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ crII}}} \right) = - ( 40 8.4 \pm 1. 3){\text{ kJ}}\;{\text{mol}}^{ - 1} and
\Updelta \textf H\textm\texto ( \text C 8 \text H 9 \text O 2 \text N,\text crIII ) = - ( 40 7.4 ±1. 3)\text kJ \text mol - 1 . \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ crIII}}} \right) = - ( 40 7.4 \pm 1. 3){\text{ kJ}}\;{\text{mol}}^{ - 1} . The proposed
\Updelta \textf H\textm\texto ( \text C 8 \text H 9 \text O 2 \text N,\text g ) \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ g}}} \right) value, together with the experimental enthalpies of formation of acetophenone and 4′-hydroxyacetophenone, taken from the
literature, and a re-evaluated enthalpy of formation of acetanilide,
\Updelta \textf H\textm\texto ( \text C 8 \text H 9 \text ON,\text g ) = - ( 10 9. 2 ± 2. 2)\text kJ \text mol - 1 , \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{ON}},{\text{ g}}} \right) = - ( 10 9. 2\,\pm\,2. 2){\text{ kJ}}\;{\text{mol}}^{ - 1} , were used to assess the predictions of the B3LYP/cc-pVTZ and CBS-QB3 methods for the enthalpy of a isodesmic and isogyric
reaction involving those species. This test supported the reliability of the theoretical methods, and indicated a good thermodynamic
consistency between the
\Updelta \textf H\textm\texto \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} (C 8H 9O 2N, g) value obtained in this study and the remaining experimental data used in the
\Updelta \textr H\textm\texto \Updelta_{\text{r}} H_{\text{m}}^{\text{o}} calculation. It also led to the conclusion that the presently recommended enthalpy of formation of gaseous acetanilide in
Cox and Pilcher and Pedley’s compilations should be corrected by ~20 kJ mol −1. 相似文献
3.
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 D solHm¥ = 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 b MX(0)L, b MX(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 C 5H 7N 2 +\mathrm{C}_{5}\mathrm{H}_{7}\mathrm{N}_{2}^{ +} in aqueous solution was calculated to be D fHmo(C 5H 7N 2+,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
4.
The 17O-NMR spin-lattice relaxation times ( T
1) of water molecules in aqueous solutions of n-alkylsulfonate (C 1 to C 6) and arylsulfonic anions were determined as a function of concentration at 298 K. Values of the dynamic hydration number,
(S -) = nh - (t c- /t c0 - 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 (t c -/t c0\tau_{\mathrm{c}}^{ -}/\tau_{\mathrm{c}}^{0}) of the rotational correlation times (t c -\tau_{\mathrm{c}}^{ -} ) of the water molecules around each sulfonate anion in the aqueous solutions to the rotational correlation time of pure water
(t c0\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 t c -/t c0\tau_{\mathrm{c}}^{ -}/\tau_{\mathrm{c}}^{0} values for alkylsulfonate anions increase with increasing ASA in the homologous-series range of C 1 to C 4, 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
5.
l-cysteine undergoes facile electron transfer with heteropoly 10-tungstodivanadophosphate,
[ \textPV\textV \textV\textV \textW 1 0 \textO 4 0 ]5 - , \left[ {{\text{PV}}^{\text{V}} {\text{V}}^{\text{V}} {\text{W}}_{ 1 0} {\text{O}}_{ 4 0} } \right]^{5 - } , at ambient temperature in aqueous acid medium. The stoichiometric ratio of [cysteine]/[oxidant] is 2.0. The products of the
reaction are cystine and two electron-reduced heteropoly blue, [PVIVVIVW10O40]7−. The rates of the electron transfer reaction were measured spectrophotometrically in acetate–acetic acid buffers at 25 °C.
The orders of the reaction with respect to both [cysteine] and [oxidant] are unity, and the reaction exhibits simple second-order
kinetics at constant pH. The pH-rate profile indicates the participation of deprotonated cysteine in the reaction. The reaction
proceeds through an outer-sphere mechanism. For the dianion −SCH2CH(NH3
+)COO−, the rate constant for the cross electron transfer reaction is 96 M−1s−1 at 25 °C. The self-exchange rate constant for the
- \textSCH2 \textCH( \textNH3 + )\textCOO - \mathord | / |
\vphantom - \textSCH2 \textCH( \textNH3 + )\textCOO - ·\textSCH2 \textCH( \textNH3 + )\textCOO - ·\textSCH2 \textCH( \textNH3 + )\textCOO - {{{}^{ - }{\text{SCH}}_{2} {\text{CH}}\left( {{{\text{NH}}_{3}}^{ + } } \right){\text{COO}}^{ - } } \mathord{\left/ {\vphantom {{{}^{ - }{\text{SCH}}_{2} {\text{CH}}\left( {{{\text{NH}}_{3}}^{ + } } \right){\text{COO}}^{ - } } {{}^{ \bullet }{\text{SCH}}_{2} {\text{CH}}\left( {{{\text{NH}}_{3}}^{ + } } \right){\text{COO}}^{ - } }}} \right. \kern-\nulldelimiterspace} {{}^{ \bullet }{\text{SCH}}_{2} {\text{CH}}\left( {{{\text{NH}}_{3}}^{ + } } \right){\text{COO}}^{ - } }} couple was evaluated using the Rehm–Weller relationship. 相似文献
6.
Apparent molar volumes ( V
2,φ
) and heat capacities ( C
p2,φ
) of glycine in known concentrations (1.0, 2.0, 4.0, 6.0, and 8.0 mol⋅kg −1) of aqueous formamide (FM), acetamide (AM), and N, N-dimethylacetamide (DMA) solutions at T=298.15 K have been calculated from relative density and specific heat capacity measurements. These measurements were completed
using a vibrating-tube flow densimeter and a Picker flow microcalorimeter, respectively. The concentration dependences of
the apparent molar data have been used to calculate standard partial molar properties. The latter values have been combined
with previously published standard partial molar volumes and heat capacities for glycine in water to calculate volumes and
heat capacities associated with the transfer of glycine from water to the investigated aqueous amide solutions, D[`( V)] 2,tro\Delta\overline{V}_{\mathrm{2,tr}}^{\mathrm{o}} and D[`( C)] p2,tro\Delta\overline{C}_{p\mathrm{2,tr}}^{\mathrm{o}} respectively. Calculated values for D[`( V)] 2,tro\Delta\overline{V}_{\mathrm{2,tr}}^{\mathrm{o}} and D[`( C)] p2,tro\Delta\overline{C}_{p\mathrm{2,tr}}^{\mathrm{o}} are positive for all investigated concentrations of aqueous FM and AM solutions. However, values for D[`( C)] p2,tro\Delta\overline{C}_{p\mathrm{2,tr}}^{\mathrm{o}} associated with aqueous DMA solutions are found to be negative. The reported transfer properties increase with increasing
co-solute (amide) concentration. This observation is discussed in terms of solute + co-solute interactions. The transfer properties
have also been used to estimate interaction coefficients. 相似文献
7.
The study elementarily investigated the effect of the cathode structure on the electrochemical performance of anode-supported
solid oxide fuel cells. Four single cells were fabricated with different cathode structures, and the total cathode thickness
was 15, 55, 85, and 85 μm for cell-A, cell-B, cell-C, and cell-D, respectively. The cell-A, cell-B, and cell-D included only
one cathode layer, which was fabricated by
( \text La0.74 \text Bi0.10 \text Sr0.16 )\text MnO3 - d \left( {{\text{La}}_{0.74} {\text{Bi}}_{0.10} {\text{Sr}}_{0.16} } \right){\text{MnO}}_{{3 - \delta }} (LBSM) electrode material. The cathode of the cell-C was composed of a
( \text La0.74 \text Bi0.10 \text Sr0.16 )\text MnO3 - d - ( \text Bi0.7 \text Er0.3 \text O1.5 ) \left( {{\text{La}}_{0.74} {\text{Bi}}_{0.10} {\text{Sr}}_{0.16} } \right){\text{MnO}}_{{3 - \delta }} - \left( {{\text{Bi}}_{0.7} {\text{Er}}_{0.3} {\text{O}}_{1.5} } \right) (LBSM–ESB) cathode functional layer and a LBSM cathode layer. Different cathode structures leaded to dissimilar polarization
character for the four cells. At 750°C, the total polarization resistance ( R
p) of the cell-A was 1.11, 0.41 and 0.53 Ω cm 2 at the current of 0, 400, and 800 mA, respectively, and that of the cell-B was 1.10, 0.39, and 0.23 Ω cm 2 at the current of 0, 400, and 800 mA, respectively. For cell-C and cell-D, their polarization character was similar to that
of the cell-B and R
p also decreased with the increase of the current. The maximum power density was 0.81, 1.01, 0.79, and 0.43 W cm −2 at 750°C for cell-D, cell-C, cell-B, and cell-A, respectively. The results demonstrated that cathode structures evidently
influenced the electrochemical performance of anode-supported solid oxide fuel cells. 相似文献
8.
The molar conductivities ( Λ) of solutions of bis(2,2′-bipyridine) bis(thiocyanate)chromium(III) triiodide [Cr III(bipy) 2(SCN) 2]I 3 (where bipy denotes 2,2′-bipyridine, C 10H 8N 2), [
_3^-\mathrm{A}^{+}\mathrm{I}_{3}^{-}
], were measured in acetonitrile (ACN) at the temperatures 294.15, 299.15, and 305.15 K. In addition, cyclic voltammograms
(CVs) of [
A +I 3-\mathrm{A}^{+}\mathrm{I}_{3}^{-}
] were recorded on platinum, gold, and glassy carbon working electrodes in ACN, using n-tetrabutylammonium hexafluorophosphate (NBu 4PF 6) as the supporting electrolyte, at scan rates ( v) ranging from 0.05 to 0.12 V⋅s −1. Furthermore, electrochemical impedance spectroscopic (EIS) measurements were carried out in the frequency range 50 Hz< f<50 kHz using these three working electrodes. The measured molar conductivities ( Λ) demonstrate that [
A +I 3-\mathrm{A}^{+}\mathrm{I}_{3}^{-}
] behaves as uni-univalent electrolyte in ACN over the investigated temperature range. The Λ values were analyzed by means of the Lee-Wheaton conductivity equation in order to estimate the limiting molar conductivities ( Λ
o), as well as the thermodynamic association constants ( K
A), at each experimental temperature for formation of [A +
I 3-\mathrm{I}_{3}^{-}
] ion-pairs. The limiting ionic conductivities (
l ±o\lambda_{\pm}^{\mathrm{o}}
), the diffusion coefficients at infinite dilution ( D
±), as well as the Stokes’ radii ( r
St) were determined for both A + and
I 3-\mathrm{I}_{3}^{-}
ions. The thermodynamic parameters for the ionic association process, i.e. the Gibbs energy (
D GAo\Delta G_{\mathrm{A}}^{\mathrm{o}}
), enthalpy (
D HAo\Delta H_{\mathrm{A}}^{\mathrm{o}}
), and entropy (
D SAo\Delta S_{\mathrm{A}}^{\mathrm{o}}
), were also determined. The mobility and diffusivity of the A + ion increase linearly with increasing temperature because the solvent medium becomes less viscous as the temperature increases.
The K
A values indicate that significant ion association occurs that is not influenced by temperature changes. The ion-pair formation
process is exothermic (
D HAo < 0\Delta H_{\mathrm{A}}^{\mathrm{o}}<0
), leading to the generation of additional entropy (
$\Delta S_{\mathrm{A}}^{\mathrm{o}}>0$\Delta S_{\mathrm{A}}^{\mathrm{o}}>0
). As a result, the Gibbs energy
D GAo\Delta G_{\mathrm{A}}^{\mathrm{o}}
is negative (
D GAo < 0\Delta G_{\mathrm{A}}^{\mathrm{o}}<0
) and the formation of
[A +I 3-][\mathrm{A}^{+}\mathrm{I}_{3}^{-}]
becomes favorable. CV studies on
[A +I 3-][\mathrm{A}^{+}\mathrm{I}_{3}^{-}]
solutions indicated that the redox pair Cr 3+/2+ appears to be quasi-reversible on a glassy carbon electrode but is completely irreversible on platinum and gold electrodes.
EIS experiments confirm that, among these three electrodes, the glassy carbon working electrode has the smallest resistance
to electron transfer. 相似文献
9.
Oxidation of 3-(4-methoxyphenoxy)-1,2-propanediol (MPPD) by bis(hydrogenperiodato) argentate(III) complex anion, [Ag(HIO 6) 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: where [IO 4
−] tot denotes the total concentration of periodate and k
a = (0.19 ± 0.04) M −1 s −1, k
b = (10.5 ± 0.3) M −2 s −1, and K
1 = (5.0 ± 0.8) × 10 −4 M at 25.0 °C and ionic strength of 0.30 M. Activation parameters associated with k
a and k
b have been calculated. A mechanism is proposed, involving two pre-equilibria, leading to formation of a periodato–Ag(III)–MPPD
complex. In the subsequent rate-determining steps, this complex undergoes inner-sphere electron-transfer from the coordinated
MPPD molecule to the metal center by two paths: one path is independent of OH −, while the other is facilitated by a hydroxide ion. 相似文献
10.
Glutathione (GSH) undergoes facile electron transfer with vanadium(V)-substituted Keggin-type heteropolyoxometalates,
[ \text PV\textV \text W 1 1 \text O 4 0 ] 4 - [ {\text{PV}}^{\text{V}} {\text{W}}_{ 1 1} {\text{O}}_{ 4 0} ]^{{ 4 { - }}} (HPA1) and
[ \text PV\textV \text V\textV \text W 1 0 \text O 4 0 ] 5 - [ {\text{PV}}^{\text{V}} {\text{V}}^{\text{V}} {\text{W}}_{ 1 0} {\text{O}}_{ 4 0} ]^{{ 5 { - }}} (HPA2). The kinetics of these reactions have been investigated in phthalate buffers spectrophotometrically at 25 °C in aqueous
medium. One mole of HPA1 consumes one mole of GSH and the product is the one-electron reduced heteropoly blue,
[ \text PV\textIV \text W 1 1 \text O 40 ] 5- [ {\text{PV}}^{\text{IV}} {\text{W}}_{ 1 1} {\text{O}}_{ 40} ]^{ 5- } . But in the GSH-HPA2 reaction, one mole of HPA2 consumes two moles of GSH and gives the two-electron reduced heteropoly blue
[ \text PV\textIV \text V\textIV \text W 10 \text O 40 ] 7- [ {\text{PV}}^{\text{IV}} {\text{V}}^{\text{IV}} {\text{W}}_{ 10} {\text{O}}_{ 40} ]^{ 7- } . Both reactions show overall third-order kinetics. At constant pH, the order with respect to both [HPA] species is one and
order with respect to [GSH] is two. At constant [GSH], the rate shows inverse dependence on [H +], suggesting participation of the deprotonated thiol group of GSH in the reaction. A suitable mechanism has been proposed
and a rate law for the title reaction is derived. The antimicrobial activities of HPA1, HPA2 and
[ \text PV\textV \text V\textV \text V\textV \text W 9 \text O 4 0 ] 6 - [ {\text{PV}}^{\text{V}} {\text{V}}^{\text{V}} {\text{V}}^{\text{V}} {\text{W}}_{ 9} {\text{O}}_{ 4 0} ]^{{ 6 { - }}} (HPA3) against MRSA were tested in vitro in combination with vancomycin and penicillin G. The HPAs sensitize MRSA towards
penicillin G. 相似文献
11.
The molar enthalpies of solution of VOSO 4⋅3.52H 2O(s) at various molalities in water and in aqueous sulfuric acid (0.1 mol⋅kg −1), Δ sol
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, D solH0m\Delta_{\mathrm{sol}}H^{0}_{\mathrm{m}}, was put forward. In terms of the improved method, the values of D solH0m=-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 VOSO 4⋅3.52H 2O(s) in water and D solH0m=-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 VOSO 4 in aqueous H 2SO 4 is higher than that in pure water. 相似文献
12.
Extraction of microamounts of cesium by a nitrobenzene solution of ammonium dicarbollylcobaltate
( \text NH 4 + \text B - ) ( {{\text{NH}}_{ 4}^{ + } {\text{B}}^{ - } }) and thallium dicarbollylcobaltate
( \text Tl + \text B - ) ( {{\text{Tl}}^{ + } {\text{B}}^{ - } }) in the presence of 2,3-naphtho-15-crown-5 (N15C5, L) has been investigated. The equilibrium data have been explained assuming
that the complexes
\text ML + {\text{ML}}^{ + } and
\text ML 2 + {\text{ML}}_{ 2}^{ + }
( \text M + = \text NH4 + ,\text Tl + ,\text Cs + ) ( {{\text{M}}^{ + } = {\text{NH}}_{4}^{ + } ,{\text{Tl}}^{ + } ,{\text{Cs}}^{ + } } ) are present in the organic phase. The stability constants of the
\text ML + {\text{ML}}^{ + } and
\text ML2 + {\text{ML}}_{2}^{ + } species
( \text M + = \text NH4 + ,\text Tl + ) ( {{\text{M}}^{ + } = {\text{NH}}_{4}^{ + } ,{\text{Tl}}^{ + } }) in nitrobenzene saturated with water have been determined. It was found that the stability of the complex cations
\text ML + {\text{ML}}^{ + } and
\text ML2 + {\text{ML}}_{2}^{ + }
(\text M + = \text NH4 + ,\text Tl + ,\text Cs + ; \text L = \text N15\text C5) ({{\text{M}}^{ + } = {\text{NH}}_{4}^{ + } ,{\text{Tl}}^{ + } ,{\text{Cs}}^{ + } ;\;{\text{L}} = {\text{N}}15{\text{C}}5}) in the mentioned medium increases in the
\text Cs + < \text NH4 + < \text Tl + {\text{Cs}}^{ + }\,<\, {\text{NH}}_{4}^{ + }\,<\,{\text{Tl}}^{ + } order. 相似文献
13.
Thermal decomposition kinetics of magnesite were investigated using non-isothermal TG-DSC technique at heating rate (β) of
15, 20, 25, 35, and 40 K min −1. The method combined Friedman equation and Kissinger equation was applied to calculate the E and lg A values. A new multiple rate iso-temperature method was used to determine the magnesite thermal decomposition mechanism function,
based on the assumption of a series of mechanism functions. The mechanism corresponding to this value of F( a), which with high correlation coefficient ( r-squared value) of linear regression analysis and the slope was equal to −1.000, was selected. And the Malek method was also
used to further study the magnesite decomposition kinetics. The research results showed that the decomposition of magnesite
was controlled by three-dimension diffusion; mechanism function was the anti-Jander equation, the apparent activation energy
( E), and the pre-exponential term ( A) were 156.12 kJ mol −1 and 10 5.61 s −1, respectively. The kinetic equation was
\frac\textda\textdT = \frac105. 6 1 bexp( - \frac18777.9T ){ \frac32(1 + a)2/3 [(1 + a)1/3 - 1] - 1 }, \frac{{{\text{d}}\alpha }}{{{\text{d}}T}} = \frac{{10^{5. 6 1} }}{\beta }\exp \left( { - \frac{18777.9}{T}} \right)\left\{ {\frac{3}{2}(1 + \alpha )^{2/3} [(1 + \alpha )^{1/3} - 1]^{ - 1} } \right\}, 相似文献
14.
MX-80 bentonite was characterized by XRD and FTIR in detail. The sorption of Th(IV) on MX-80 bentonite was studied as a function
of pH and ionic strength in the presence and absence of humic acid/fulvic acid. The results indicate that the sorption of
Th(IV) on MX-80 bentonite increases from 0 to 95% at pH range of 0–4, and then maintains high level with increasing pH values.
The sorption of Th(IV) on bentonite decreases with increasing ionic strength. The diffusion layer model (DLM) is applied to
simulate the sorption of Th(IV) with the aid of FITEQL 3.1 mode. The species of Th(IV) adsorbed on bare MX-80 bentonite are
consisted of “strong” species
o \text YOHTh4 + \equiv {\text{YOHTh}}^{4 + } at low pH and “weak” species
o \text XOTh( OH) 3 \equiv {\text{XOTh(OH)}}_{3} at pH > 4. On HA bound MX-80 bentonite, the species of Th(IV) adsorbed on HA-bentonite hybrids are mainly consisted of
o \text YOThL3 \equiv {\text{YOThL}}_{3} and
o \text XOThL1 \equiv {\text{XOThL}}_{1} at pH < 4, and
o \text XOTh( OH) 3 \equiv {\text{XOTh(OH)}}_{3} at pH > 4. Similar species of Th(IV) adsorbed on FA bound MX-80 bentonite are observed as on FA bound MX-80 bentonite. The
sorption isotherm is simulated by Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models, respectively. The sorption mechanism
of Th(IV) on MX-80 bentonite is discussed in detail. 相似文献
15.
The formation of large even-numbered carbon cluster anions,
\text C\textn - {\text{C}}_{\text{n}}^{ - } , with n up to 500 were observed in the mass spectra generated by laser ablation of graphene and graphene oxide, and the signal
intensity of the latter is much weaker than that of the former. The cluster distributions generated from graphene can be readily
altered by changing the laser energy and the accumulation period in the FT - ICR cell. By choosing suitable experimental conditions,
weak signals of odd-numbered anions from
\text C125 - {\text{C}}_{{125}}^{ - } to
\text C211 - {\text{C}}_{{211}}^{ - } , doubly charged anions from
\text C702 - {\text{C}}_{{70}}^{{2 - }} to
\text C2302 - {\text{C}}_{{230}}^{{2 - }} and triply charged cluster anions from
\text C803 - {\text{C}}_{{80}}^{{3 - }} to
\text C2243 - {\text{C}}_{{224}}^{{3 - }} can be observed. Tandem MS was applied to some selected cluster anions. Though no fragment anions larger than
\text C20 - {\text{C}}_{{20}}^{ - } can be observed by the process of collisional activation with N 2 gas for most cluster ions, several cluster anions can lose units of C 2, C 4, C 6 or C 8 in their collision process. The differences in their dissociation kinetics and structures require further calculations and
experimental studies. 相似文献
16.
The stoichiometries, kinetics and mechanism of the reduction of tetraoxoiodate(VII) ion, IO 4
− to the corresponding trioxoiodate(V) ion, IO 3
− by n-(2-hydroxylethyl)ethylenediaminetriacetatocobaltate(II) ion, [CoHEDTAOH 2] − have been studied in aqueous media at 28 °C, I = 0.50 mol dm −3 (NaClO 4) and [H +] = 7.0 × 10 −3 mol dm −3. The reaction is first order in [Oxidant] and [Reductant], and the rate is inversely dependent on H + concentration in the range 5.00 × 10 −3 ≤ H +≤ 20.00 × 10 −3 mol dm −3 studied. A plot of acid rate constant versus [H +] −1 was linear with intercept. The rate law for the reaction is:
- \frac[ \textCoHEDTAOH2 - ]\textdt = ( a + b[ \textH + ] - 1 )[ \textCoHEDTAOH2 - ][ \textIO4 - ] - {\frac{{\left[ {{\text{CoHEDTAOH}}_{2}^{ - } } \right]}}{{{\text{d}}t}}} = \left( {a + b\left[ {{\text{H}}^{ + } } \right]^{ - 1} } \right)\left[ {{\text{CoHEDTAOH}}_{2}^{ - } } \right]\left[ {{\text{IO}}_{4}^{ - } } \right] 相似文献
17.
The oxidation of aquaethylenediaminetetraacetatocobaltate(II) [Co(EDTA)(H 2O)] −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
19.
Theoretical study of several para-substituted O-nitrosyl carboxylate compounds has been performed using density functional B3LYP method with 6-31G(d,p) basis set. Geometries obtained from DFT calculation were used to perform natural bond orbital analysis. It is noted that weakness in the O 3–N 2 sigma bond is due to $ n_{{{\text{O}}_{1} }} \to \sigma_{{{\text{O}}_{3} - {\text{N}}_{2} }}^{*} Theoretical study of several para-substituted O-nitrosyl carboxylate compounds has been performed using density functional B3LYP method with 6-31G(d,p) basis set. Geometries
obtained from DFT calculation were used to perform natural bond orbital analysis. It is noted that weakness in the O3–N2 sigma bond is due to
n\textO1 ? s\textO3 - \textN2 * n_{{{\text{O}}_{1} }} \to \sigma_{{{\text{O}}_{3} - {\text{N}}_{2} }}^{*} delocalization and is responsible for the longer O3–N2 bond lengths in para-substituted O-nitrosyl carboxylate compounds. It is also noted that decreased occupancy of the localized
s\textO3 -\textN2 \sigma_{{{\text{O}}_{3} --{\text{N}}_{2} }} orbital in the idealized Lewis structure, or increased occupancy of
s\textO3 - \textN2 * \sigma_{{{\text{O}}_{3} - {\text{N}}_{2} }}^{*} of the non-Lewis orbital, and their subsequent impact on molecular stability and geometry (bond lengths) are related with
the resulting p character of the corresponding sulfur natural hybrid orbital of
s\textO3 -\textN2 \sigma_{{{\text{O}}_{3} --{\text{N}}_{2} }} bond orbital. In addition, the charge transfer energy decreases with the increase of the Hammett constants of substituent
groups and the partial charges distribution on the skeletal atoms may approve anticipating that the electrostatic repulsion
or attraction between atoms can give a significant contribution to the intra- and intermolecular interaction. 相似文献
20.
Molar heat capacity measurement on Na 2TeO 4(s) and TiTe 3O 8(s) were carried out using differential scanning calorimeter. The molar heat capacity values were least squares analyzed and the dependence of molar heat capacity with temperature for Na 2TeO 4(s) and TiTe 3O 8(s) can be given as, $$ \begin{gathered} {\text{C}}^{\text{o}}_{{{\text{p}},{\text{m}}}} \left\{ {{\text{Na}}_{ 2} {\text{TeO}}_{ 4} \left( {\text{s}} \right)} \right\} \,={159}.17 { } + 1.2\,\times\,10^{-4}T-{55}.34\,\times\,10^{5}/T^{2};\hfill \\ C^{\text{o}}_{{{\text{p}},{\text{m}}}} \left\{ {{\text{TiTe}}_{ 3} {\text{O}}_{ 8} \left( {\text{s}} \right)} \right\}\,=\,{ 275}.22{ }+{4}.0\,\times\, 10^{-5}T-{58}.28\,\times\,10^{5}/T^{2};\hfill \\ \end{gathered} $$ From this data, other thermodynamic functions were evaluated. 相似文献
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