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1.
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
2.
The two-state reaction mechanism of the Pt 4+/− with N 2O (CO) on the quartet and doublet potential energy surfaces has been investigated at the B3LYP level. The effect of Pt 4
− anion assistance is analyzed using the activation strain model in which the activation energy (Δ Ε
≠) is decomposed into the distortion energies
(\Updelta E 1 \textdist ) (\Updelta E^{ \ne }_{\text{dist}} ) and the stabilizing transition state (TS) interaction energies
(\Updelta E 1 \textint ) (\Updelta E^{ \ne }_{\text{int}} ) , namely
\Updelta E 1 = \Updelta E 1 \textdist + \Updelta E 1 \textint \Updelta E^{ \ne } = \Updelta E^{ \ne }_{\text{dist}} + \Updelta E^{ \ne }_{\text{int}} . The lowering of activation barriers through Pt 4
− anion assistance is caused by the TS interaction
\Updelta E 1 \textint \Updelta E^{ \ne }_{\text{int}} (−90.7 to −95.6 kcal/mol) becoming more stabilizing. This is attributed to the N 2O π*-LUMO and Pt d HOMO back-donation interactions. However, the strength of the back-donation interactions has significantly
impact on the reaction mechanism. For the Pt 4
− anion system, it has very significant back-bonding interaction (N 2O negative charge of 0.79e), HOMO has 81.5% π* LUMO(N 2O) character, with 3d orbital contributions of 10.7% from Pt (3) and 7.7% from Pt (7) near the 4TS4 transition state. This facilitates the bending of the N 2O molecule, the N–O bond weakening, and an O −( 2P) dissociation without surface crossing. For the Pt 4
+ cation system, the strength of the charge transfer is weaker, which leads to the diabatic (spin conserving) dissociation
of N 2O: N 2O( 1∑ +) → N 2( 1∑ g+) + O( 1D). The quartet to doublet state transition should occur efficiently near the 4TS1 due to the larger SOC value calculated of 677.9 cm −1. Not only will the reaction overcome spin-change-induced barrier (ca. 7 kcal/mol) but also overcome adiabatic barrier (ca.
40.1 kcal/mol).Therefore, the lack of a thermodynamic driving force is an important factor contributing to the low efficiency
of the reaction system. 相似文献
3.
This article reports the values of the standard ( p
o = 0.1 MPa) molar enthalpies of formation, in the gaseous phase,
\Updelta \textf H\textm\texto ( \text g ), {{\Updelta}}_{\text{f}} H_{\text{m}}^{\text{o}} \left( {\text{g}} \right), at T = 298.15 K, of 2-acetyl-5-nitrothiophene and 5-nitro-2-thiophenecarboxaldehyde as −(48.8 ± 1.6) and (4.4 ± 1.3) kJ mol −1, respectively. These values were derived from experimental thermodynamic parameters, namely, the standard ( p
o = 0.1 MPa) molar enthalpies of formation, in the crystalline phase,
\Updelta \textf H\textm\texto ( \text cr ) , {{\Updelta}}_{\text{f}} H_{\text{m}}^{\text{o}} \left( {\text{cr}} \right) , at T = 298.15 K, obtained from the standard molar enthalpies of combustion,
\Updelta \textc H\textm\texto , {{\Updelta}}_{\text{c}} H_{\text{m}}^{\text{o}} , measured by rotating bomb combustion calorimetry, and from the standard molar enthalpies of sublimation, at T = 298.15 K, determined from the temperature–vapour pressure dependence, obtained by the Knudsen mass loss effusion method.
The results are interpreted in terms of enthalpic increments and the enthalpic contribution of the nitro group in the substituted
thiophene ring is compared with the same contribution in other structurally similar compounds. 相似文献
4.
The apparent molar volumes ( V
φ
) of glycine, L-alanine and L-serine in aqueous 0 to 4 mol⋅kg −1 N-methylacetamide (NMA) solutions have been obtained by density measurement at 298.15 K. The standard partial molar volumes
( Vf0)V_{\phi}^{0}) and standard partial molar volumes of transfer (D trVf0)\Delta_{\mathrm{tr}}V_{\phi}^{0}) have been determined for these amino acids. It has been show that hydrophilic-hydrophilic interactions between the charged
groups of the amino acids and the –CONH– group of NMA predominate for glycine and L-serine, but for L-alanine the interactions
between its side group (–CH 3) and NMA predominate. The –CH 3 group of L-alanine has much more influence on the value of D trVf0\Delta_{\mathrm{tr}}V_{\phi}^{0} than that of the –OH group of L-serine. The results have been interpreted in terms of a co-sphere overlap model. 相似文献
5.
Densities, viscosities, and refractive indices of three amino acids (glycine, L-alanine, and L-valine) in aqueous solutions
of an ionic liquid, 1-propyl-3-methylimidazolium bromide, have been measured at 298.15 K. These data have been used to calculate
apparent molar volumes ( V
φ
), viscosity B-coefficients, and molar refractions of these mixtures. The standard partial molar volumes ( Vf0V_{\phi}^{0}) and standard partial molar volumes of transfer (D trVf0\Delta_{\mathrm{tr}}V_{\phi}^{0}) have been determined for these amino acid solutions from these density data. The resulting values of Vf0V_{\phi}^{0} and D trVf0\Delta_{\mathrm{tr}}V_{\phi}^{0} for transfer of amino acids from water to aqueous ionic liquid solutions have been interpreted in terms of solute + solvent
interactions. These data also indicate that hydrophobic interactions predominate in L-alanine and L-valine solutions. Linear
correlations were found for both Vf0V_{\phi}^{0} and the viscosity B-coefficient with the number of carbon atoms in the alkyl chain of the amino acids, and have been used to estimate the contribution
of the charged end groups (NH 3+\mathrm{NH}_{3}^{+}, COO −), the CH 2 group, and other alkyl chains of the amino acids. The viscosity and molar refractivity results have been used to confirm
the conclusions obtained from volumetric properties. 相似文献
6.
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
7.
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
8.
Dilatometric measurements of excess molar volumes, VE and excess partial molar volumes, [`( V)] \texti\textE\overline V _{\text{i}}^{\text{E}} have been made for binary mixtures of acetonitrile with 1,2-ethanediol, 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, and 1,2-hexanediol at 20°C over the entire composition range. VE for acetonitrile + 1,2-ethanediol and 1,2-propanediol mixtures are negative over the entire range of mole fractions and positive values are obtained for all remaining mixtures. The results are explained in terms of dissociation of the self-associated 1,2-alkanediol molecules and the formation of aggregates between unlike molecules through O—H...N=C hydrogen bonding. From the experimental results, VE were calculated and correlated by Redlich–Kister type function in terms of mole fractions. The excess partial molar volumes were extrapolated to zero concentration to obtain the limiting values at infinite dilution, [`( V)] \texti\textE,o\overline V _{\text{i}}^{{\text{E,o}}}
. 相似文献
9.
The enthalpies of dissolution in ethyl acetate and acetone of hexanitrohexaazaisowurtzitane (CL-20) were measured by means
of a RD496-2000 Calvet microcalorimeter at 298.15 K, respectively. Empirical formulae for the calculation of the enthalpy
of dissolution (Δ diss
H), relative partial molar enthalpy (Δ diss
H
partial), relative apparent molar enthalpy (Δ diss
H
apparent), and the enthalpy of dilution (Δ dil
H
1,2) of each process were obtained from the experimental data of the enthalpy of dissolution of CL-20. The corresponding kinetic
equations describing the two dissolution processes were
\frac\text da\text dt = 1.60 ×10 - 2 (1 - a) 0.84 {\frac{{{\text{d}}\alpha }}{{{\text{d}}t}}} = 1.60 \times 10^{ - 2} (1 - \alpha )^{0.84} for dissolution process of CL-20 in ethyl acetate, and
\frac\text da\text dt = 2.15 ×10 - 2 (1 - a) 0.89 {\frac{{{\text{d}}\alpha }}{{{\text{d}}t}}} = 2.15 \times 10^{ - 2} (1 - \alpha )^{0.89} for dissolution process of CL-20 in acetone. 相似文献
10.
Densities, viscosities and ultrasonic speeds of sound for binary mixtures of 1,2-dimethoxyethane (DME) with benzene, toluene,
chlorobenzene, benzyl chloride, benzaldehyde, nitrobenzene, and aniline are reported over the entire composition range at
ambient pressure and temperature (i.e., T=298.15 K and p=1.01×10 5 Pa). These experimental data were utilized to derive the excess molar volumes ( VmEV_{\mathrm{m}}^{\mathrm{E}}), excess viscosities ( η
E), and various acoustic parameters including the deviation in isentropic compressibility (Δ κ
S
), internal pressure ( π
I), and excess enthalpy ( H
E). From the excess molar volumes ( VmEV_{\mathrm{m}}^{\mathrm{E}}), the excess partial molar volumes ([`( V)] m,1E\overline{V}_{\mathrm{m},1}^{\mathrm{E}} and [`( V)] m,2E\overline{V}_{\mathrm{m},2}^{\mathrm{E}}) and excess partial molar volumes at infinite dilution ([`( V)] m,10,E\overline{V}_{\mathrm{m},1}^{0,\mathrm{E}} and [`( V)] m,20,E\overline{V}_{\mathrm{m},2}^{0,\mathrm{E}}) were derived and discussed for each liquid component in the mixtures. The excess/deviation properties were found to be either
negative or positive, depending on the molecular interactions and the nature of the liquid mixtures. 相似文献
11.
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
12.
The solubilities of N-[tris(hydroxymethyl)methyl]-3-aminopropanesulfonic acid (TAPS) or N-[tris(hydroxymethyl)methyl]-3-amino-2-hydroxypropanesulfonic
acid (TAPSO) in water and in aqueous solutions of CH 3COOK (KAc), KBr, KCl, or NaCl were determined from density measurements at 298.15 K. The solubilities of TAPS in aqueous solution
decrease with increasing concentration of the salts (salting-out effect), whereas those of TAPSO increase with increasing
concentration of the salts (salting-in effect). The solubility and density data were further used to calculate the apparent
transfer Gibbs energies, Δ tr
G, and transfer molar volumes, D trVfo\Delta_{\mathrm{tr}}V_{\phi}^{\mathrm{o}}, of these buffers from water to aqueous electrolyte solutions at 298.15 K. The contributions of various functional groups
of TAPS, TAPSO, and the related buffers (tris(hydroxymethyl)aminomethane, TRIS, and N-tris[hydroxymethyl]-4-amino-butanesulfonic
acid, TABS) to the transfer properties were systematically estimated from the calculated Δ tr
G and D trVfo\Delta_{\mathrm{tr}}V_{\phi}^{\mathrm{o}}. 相似文献
13.
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
14.
A ternary binuclear complex of dysprosium chloride hexahydrate with m-nitrobenzoic acid and 1,10-phenanthroline, [Dy( m-NBA) 3phen] 2·4H 2O ( m-NBA: m-nitrobenzoate; phen: 1,10-phenanthroline) was synthesized. The dissolution enthalpies of [2phen·H 2O(s)], [6 m-HNBA(s)], [2DyCl 3·6H 2O(s)], and [Dy( m-NBA) 3phen] 2·4H 2O(s) in the calorimetric solvent (V DMSO:V MeOH = 3:2) were determined by the solution–reaction isoperibol calorimeter at 298.15 K to be
\Updelta \texts H\textmq \Updelta_{\text{s}} H_{\text{m}}^{\theta } [2phen·H 2O(s), 298.15 K] = 21.7367 ± 0.3150 kJ·mol −1,
\Updelta \texts H\textmq \Updelta_{\text{s}} H_{\text{m}}^{\theta } [6 m-HNBA(s), 298.15 K] = 15.3635 ± 0.2235 kJ·mol −1,
\Updelta \texts H\textmq \Updelta_{\text{s}} H_{\text{m}}^{\theta } [2DyCl 3·6H 2O(s), 298.15 K] = −203.5331 ± 0.2200 kJ·mol −1, and
\Updelta \texts H\textmq \Updelta_{\text{s}} H_{\text{m}}^{\theta } [[Dy( m-NBA) 3phen] 2·4H 2O(s), 298.15 K] = 53.5965 ± 0.2367 kJ·mol −1, respectively. The enthalpy change of the reaction was determined to be
\Updelta \textr H\textmq = 3 6 9. 4 9 ±0. 5 6 \text kJ·\text mol - 1 . \Updelta_{\text{r}} H_{\text{m}}^{\theta } = 3 6 9. 4 9 \pm 0. 5 6 \;{\text{kJ}}\cdot {\text{mol}}^{ - 1} . According to the above results and the relevant data in the literature, through Hess’ law, the standard molar enthalpy of
formation of [Dy( m-NBA) 3phen] 2·4H 2O(s) was estimated to be
\Updelta \textf H\textmq \Updelta_{\text{f}} H_{\text{m}}^{\theta } [[Dy( m-NBA) 3phen] 2·4H 2O(s), 298.15 K] = −5525 ± 6 kJ·mol −1. 相似文献
15.
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
16.
Twelve surfactant Schiff base ligands were synthesized from salicylaldehyde and its chloro-, bromo- and methoxy- derivatives
by condensation with long-chain aliphatic primary amines, and a number of mixed ligand cobalt(III) surfactant Schiff base
coordination complexes of the type [Co(trien)A] 2+ were synthesized from the corresponding dihalogeno complexes by ligand substitution. The Schiff bases and their complexes
were characterized by physico-chemical and spectroscopic methods. The complexes form foams in aqueous solution upon shaking.
The critical micelle concentration (CMC) values of the complexes in aqueous solution were obtained from conductance measurements.
Specific conductivity data (at 303–323 K) served for the evaluation of the thermodynamics of micellization (
\Updelta G\textm0 \Updelta G_{\text{m}}^{0} ,
\Updelta H\textm0 \Updelta H_{\text{m}}^{0} ,
\Updelta S\textm0 \Updelta S_{\text{m}}^{0} ). The complexes were tested for its antimicrobial activity. 相似文献
17.
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
18.
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
19.
The assumption that potassium permanganate may serve as a kinetics standard in solid decomposition kinetics made a priori
on the basis of the mechanism of the congruent dissociative vaporization of KMnO 4 and its crystal structure was successfully supported experimentally. As expected, the decomposition rate of KMnO 4 does not depend on the kind of foreign gas (He, air, CO 2 and Ar) and on the measurement technique (isothermal or dynamic). Other requirements for KMnO 4 as an ideal kinetics standard are satisfied as well. The use of the third-law method for determining the molar enthalpy of
a reaction
( \Updelta \textr H\textT\texto / n ) \left( {\Updelta_{\text{r}} H_{\text{T}}^{\text{o}} / \nu } \right) provides an excellent reproducibility of results. The mean value of
\Updelta \textr H\textT\texto / n \Updelta_{\text{r}} H_{\text{T}}^{\text{o}} / \nu from 12 experiments in different gases is 138.3 ± 0.6 kJ mol −1, which coincides with the value of 138.1 kJ mol −1 calculated from the isothermal measurements in different gases by the second-law method. As predicted by theory, the random
errors of the second-law and Arrhenius plot methods are 10–20 times greater. In addition, the use of these methods in the
case of dynamic measurements is related to large systematic errors caused by an inaccurate selection of the geometrical (contraction)
model. The third-law method is practically free of these errors. 相似文献
20.
The effect of some prepared compounds, namely 3,5-dimethyl-1 H-pyrazole (P1), 3(5)-amino-5(3)-methylpyrazole (P2), and 1′,3,5,5′-tetramethyl-1′ H-1,3′-bipyrazole (P3), on the corrosion behaviour of steel in 1.0 M hydrochloric acid solution as corrosive medium has been investigated at 308 K using weight-loss measurement, potentiodynamic
polarisation, linear polarisation, and impedance spectroscopy (EIS). Generally, inhibition efficiency of the investigated
compounds was found to depend on the concentration and nature of the inhibitor. P3 was a better inhibitor than P1 and P2,
and its inhibition efficiency increased with increasing concentration of inhibitor, attaining 94% above 10 −3
M. Potentiodynamic polarisation studies clearly reveal that P3 acts essentially as a cathodic inhibitor. E (%) values obtained from different methods are in reasonably good agreement. EIS measurements show an increase of transfer
resistance with inhibitor concentration. Partial π-charge on atoms was calculated. Correlation between the highest occupied
molecular orbital energy E
HOMO and inhibition efficiencies was sought. The temperature effect on the corrosion behaviour of steel in 1.0 M HCl without and with different concentrations of inhibitor P3 was studied in the temperature range 308 to 343 K. Thermodynamic
data, for example heat of adsorption (
\Updelta H\textads° \Updelta H_{\text{ads}}^{^\circ } ), entropy of adsorption (
\Updelta S\textads° \Updelta S_{\text{ads}}^{^\circ } ) and free energy of adsorption (
\Updelta G\textads° \Updelta G_{\text{ads}}^{^\circ } ) were calculated by use of thermodynamic equations. Kinetic activation data, for example E
a, Δ H*, Δ S* and pre-exponential factor, were calculated, and are discussed. The inhibiting action of P3 on the corrosion of steel in
1–10 M hydrochloric acid was also studied by weight-loss measurement. The rate constant and reaction constant were calculated for
the corrosion reactions. Adsorption of P3 on the steel surface in 1.0 M HCl follows the Langmuir isotherm model. 相似文献
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