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1.
The interfacial tension of lauric, myristic and palmitic acids at the dodecane/water interface and of their sodium salts at the air/water interface were measured using the Du Noüy (ring) method. On the basis of these results the standard free energies of adsorption (ΔG0ad) and of micellization (ΔG0mic) of the above mentioned systems were calculated. According to deviations of the Langmuir isotherm, the corresponding interactions were discussed from the dependence of the standard free energy of adsorption on the interface coverage (Θ).  相似文献   

2.
The standard thermodynamic quantities, ΔG0, ΔH0, and ΔS0, associated with the ionization process of benzoic acid in formamide have been evaluated. The standard potentials of the Ag(s)/AgCNS(s)/CNS and the Ag(s)/Ag3Ci(s)/Ci3− electrode, and the standard thermodynamic quantities for the electrode processes have been calculated in formamide, at different temperatures.  相似文献   

3.
The e.m.f. of the galvanic cells Pt,C,Te(l),NiTeO3,NiO/15 YSZ/O2 (Po2 = 0.21 atm),Pt and Pt,C,NiTeO3,Ni3TeO6,NiO/15 YSZ/O2 (Po2 = 0.21 atm),Pt (where 15 YSZ=15 mass% yttria-stabilized zirconia) was measured over the ranges 833–1104 K and 624–964 K respectively, and could be represented by the least-squares expressions E(1)±1.48 (mV) = 888.72 − 0.504277 (K) and E(II) ±4.21 (mV) = 895.26 − 0.81543T (K).

After correcting for the standard state of oxygen in the air reference electrode, and by combining with the standard Gibbs energies of formation of NiO and TeO2 from the literature, the following expressions could be derived for the ΔG°f of NiTeO3 and Ni3TeO6: ΔGf°(NiTeO3) ± 2.03 (kJ mol−1) = −577.30 + 0.26692T (K) and ΔG°f(Ni3TeO6)±2.54 (kJ mol−1) = −1218.66 + 0.58837T (K).  相似文献   


4.
Medium-resolution spectra of the N2 b1Πu-X1Σg+ band system were recorded by 1 + 1 multiphoton ionization. In the spectra we found different linewidths for transitions to different vibrational levels in the b 1Πu state: Δν0 = 0.50 ± 0.05 cm−1, Δν1 = 0.28 ± 0.02 cm−1, Δν2 = 0.65 ± 0.06 cm−1, Δν3 = 3.2 ± 0.5 cm−1, Δν4 = 0.60 ± 0.07 cm−1, and Δν5 = 0.28 ± 0.02 cm−1. From these linewidths, predissociation lifetimes τν were obtained: τ0 = 16 ± 3 ps, τ1 > 150 ps, τ2 = 10 ± 2 ps, τ3 = 1.6 ± 0.3 ps, τ4 = 9 ± 2 ps, and τ5 > 150 ps. Band origins and rotational constants for the b 1Πuν = 0 and 1 levels were determined for the 14N2 and 14N15N molecules.  相似文献   

5.
Manganese hydrogen phosphate monohydrate, MnHPO4·H2O, a new phase, is synthesized. Its solubility is investigated in the temperature range 35–50°C and pH range 3.4–7.5. Ksp, ΔH0, ΔS0 and ΔG0 for the dissolution are reported. The decrease in solubility with increase in pH is explained as due to a surface coating of insoluble basic phosphate.  相似文献   

6.
The temperature dependence of chiral separations was investigated in combined system of reversed-phase (RP) liquid chromatography using two chiral additives: single or β native cyclodextrins and their permethylated derivatives. The model tested compounds of pharmaceutical interest were: methylphenobarbital, mephenytoin, morsuximide and camphor. Taking the localization of a complexation process as a criterion – the combined system with two selectors has been rationalized as occurring in three stages. The influence of temperature (in narrow range of 20°C) on retention and enantioselectivity was studied in; System I (complexation occurs in the mobile phase), in System II (complexation on the stationary phase) and in System III (complexation in both phases together). In System III (as for System I) it has been found that the model compounds could be classified into three groups based on their retention dependence on temperature: retention decrease with temperature decrease, retention increase with temperature decrease or no influence of temperature on retention. For all the compounds investigated, decrease in temperature increases the selectivity. Standard enthalpy (ΔH0) and entropy (ΔS0) changes of solute transfer between the mobile and the stationary phase and standard enthalpy (ΔH0CD) and entropy (ΔS0CD) changes of complex formation were also calculated. In Systems I and III, if the complexation in the mobile phase is favored process compared with interaction with the stationary phases (RP or covered by permethylated cyclodextrin), the shortest retention time and the best selectivity is observed at low temperature.  相似文献   

7.
The thermodynamic data (ΔG0, ΔH0 and TΔS0) of the solvation of tetraphenylarsonium-tetraphenylborate (Ph4AsPh4B) and its neutral parts, tetraphenylgermanium (Ph4Ge) and tetraphenylmethane (Ph4C) in methanol—N,N-dimethylformamide mixed solvents are discussed.

The values of the free energy of transfer, ΔsMG0, are calculated from measurements of the solubilities of Ph4AsPh4B, Ph4Ge and Ph4C in the successive fractions of MeOH in DMF at three different temperatures (15, 25, 35°C). The values of ΔsMH0 and TΔsMS0 for the derivatives are calculated from ΔsMG0 values.

The values of ΔsMG0, ΔsMH0 and TΔsMS0 of tetraphenylarsonium and tetraphenylborate ions have also been carefully calculated. The ratios of ΔsMG0 values (ΔsMG0 = ΔG0(+)/ΔG0(−)) were found to be greater than unity. Similarly, the ratios of ΔsMH0 and TΔsMS0 for the positive and negative ions were found to be greater than unity.  相似文献   


8.
The and -benzyl derivatives (1 and 2, respectively) of (+)-camphor have been synthesized and are found to exert a strong influence on the circular dichroism n→π* Cotton effects: 1: Δε301max -0.36 (n- heptane) and 2: Δε302max +3.22, relative to camphor: Δε304max +1.8 (n-heptane). Evidence for electric dipole transition moment coupling in these γ, δ -unsaturated systems is found in the n→π* UV: 1: ε291max 84 (n-heptane) and 2: ε285max 303, relative to camphor: ε290max 25.  相似文献   

9.
The standard potentials of silver—silver bromide and silver—silver iodide electrodes in glycerol+water mixtures containing 5, 10, 20 and 30 wt% glycerol were determined from electromotive force measurements of the cell Ag(s), AgX(s), KX(c)//KCl(c), AgCl(s), Ag(s), where X is Br or I, at seven different temperatures in the range 5–35°C. The standard potentials in each solvent are represented as a function of temperature. The standard thermodynamic functions for the electrode reactions, the primary medium effects of various solvents upon X, and the standard thermodynamic quantities for the transfer of 1 g-ion of X from water to the respective glycerol + water media are evaluated and discussed in the light of ion—solvent interactions as well as the structural changes of the solvents. From the values of the Ag/Ag+ and Ag/AgX, X electrodes, the thermodynamic solubility product constants of silver chloride, silver bromide and silver iodide have been determined in glycerol + water solvent mixtures at different temperatures.  相似文献   

10.
The gaseous equilibria involving the molecules AuSi, AuSi2 and Au2Si have been studied by means of the Knudsen effusion technique combined with mass spectrometric analysis of the vapor. The experimentally determined reaction enthalpies were combined with appropriate literature data to obtain the following atomization energies (in kJ mole−1): D00[AuSi(g)] = 301.0 ± 6.0, D00[Au2Si(g)] = 582.7 ± 15 and D00[AuSi2(g)] = 602.1 ± 15. The corresponding D0298 values are: 305.2 ± 6.0, 589.1 ± 15 and 610.5 ± 15, and the standard heats of formation, ΔH0f,298, 518.6, 602.9 and 668.9, respectively.

Comparison of the atomization energies of these silicon—gold molecules with the literature values for the corresponding germanium—gold and tin—gold molecules indicates similarity in the nature of bonding.  相似文献   


11.
ΔG0, ΔH0 and ΔS0 protonation values of some pairs of diastereoisomeric dipeptides have been determined by potentiometry and calorimetry in aqueous solution at 25°C and I = 0.1 mol dm−3 (KNO3). On the basis of the results obtained it has been possible to assess the role played by two different non-covalent interactions, namely the electrostatic interaction and the solvophobic interaction, on the thermodynamic stereoselectivity in the proton complex formation, shown by the systems investigated.  相似文献   

12.
The heats of formation of six radical cations have been calculated using ab initio MO methods at the MP4/6-31 + G(2df, p) level with MP2/6-31G(d, p)-optimized geometries. The theoretical values for ΔH0f,298 (kJ/mol) of the radical ions considered are (experimental values in parentheses): methanol CH3OH+√: 854 (845); methyleneoxonium CH2OH+√2: 815 (816); methyleneimine CH2NH+√: 1076 (1054); aminomethylene HCNH+√2: 1040 (1079); methylamine CH3NH+√2: 863 (843) and methyleneammonium CH2NH+√3: 855 (958). The calculated results thus confirm the discrepancy between experiment and theory on the heats of formation of nitrogen-containing radical cations. In the latter, the distonic species are calculated to be more stable than their classical isomers. The higher stability of the distonic ions has also been discussed. The recommended heat of formation of the methyleneiminium cation CH2NH+2 is 754 kJ/mol.  相似文献   

13.
Saran L  Cavalheiro E  Neves EA 《Talanta》1995,42(12):2027-2032
The highly neutralized ethylenediaminetetraacetate (EDTA) titrant (95–99% as Y4− anion) precipitates with Ag+ cations to form the Ag4Y species, in aqueous medium, which is well characterized from conductometric titration, thermal analysis and potentiometric titration of the silver content of the solid. The precipitate dissolves in excess Y4− to form a complex, AgY3−. Equilibrium studies at 25°C and ionic strength 0.50 M (NaNO3) have shown from solubility and potentiometric measurements that the formation constant (95% confidence level) β1 = (1.93 ± 0.07) × 105 M−1 and the solubility products are KS0 = [Ag +]4[Y4−] = (9.0 ± 0.4) × 10−18 M5 and KS1 = [Ag +]3[AgY3−] = (1.74 ± 0.08) × 10−12 M4. The presence of Na+, rather than ionic strength, markedly affects the equilibrium; the data at ionic strength 0.10 M are: β1 = (1.19 ± 0.03) × 106 M−1, KS0 = (1.6 ± 0.4) × 10−19 M5 and KS1 = (1.9 ± 0.5) × 10−13 M4; at ionic strength tending to zero; β1 = (1.82 ± 0.05) × 107 M−1, KS0 = (2.6 ± 0.8) × 10−22 M5 and KS1 = (5 ± 1) × 10−15 M4. The intrinsic solubility is 2.03 mM silver (I) in 0.50 M NaNO3. Well-defined potentiometric titration curves can be taken in the range 1–2 mM with the Ag indicator electrode. Thermal analysis revealed from differential scanning calorimetry a sharp exothermic peak at 142°C; thermal gravimetry/differential thermal gravimetry has shown mass loss due to silver formation and a brown residue, a water-soluble polymeric acid (decomposition range 135–157°C), tending to pure silver at 600°C, consistent with the original Ag4Y salt.  相似文献   

14.
The fraction FΣ of excited-state oxygen formed as b 1Σg+ was determined for a series of triplet-state photosensitizers in CCl4 solutions. FΣ was determined by monitoring the intensities of (a) O2(b 1Σg+) fluorescence at 1926 nm (O2(b 1Σg+)→O2(a 1Δg) and (b) O2(a 1 Δg) phosphorescence at 1270 nm (O2(a 1Δg) → O2(X3Σg)). Oxygen excited states were formed by energy transfer from substituted benzophenones and acetophenones. The data indicate that FΣ depends on several variables including the orbital configuration of the lowest triplet state and the triplet-state energy. The available data indicate that the sensitizer-oxygen charge transfer (CT) state is not likely to influence FΣ strongly by CT-mediated mixing of various sensitizer-oxygen states.  相似文献   

15.
The heat capacities of NaNO3 and KNO3 were determined from 350 to 800 K by differential scanning calorimetry. Solid-solid transitions and melting were observed at 550 and 583 K for NaNO3 and 406 and 612 K for KNO3, respectively. The entropies associated with the solid-solid transitions were measured to be (8.43± 0.25) J K−1 mole−1 for NaNO3 and (13.8±0.4) J K−1 mole−1 for KNO3. At 298.15 K the values of C0P S0P, {H0(T)-H0(0)}/T and -{G0(T)-H0(0)}/T, respectively, are 91.94, 116.3, 57.73, and 58.55 J K−1 mole−1 for NaNO3 and 95.39, 133.0, 62.93, and 70.02 J K−1 mole−1 for KNO3. Values for S0T, {H0(T)-H0(0)}/T, and -{G0(T)-H0(0)}/T were calculated and tabulated from 15 to 800 K for NaNO3 and KNO3.  相似文献   

16.
《Thermochimica Acta》1991,190(2):319-323
Measurements were made of the dissolution heats of NaBPh4 and Ph4PCl in water-n-propanol mixtures over the whole range of compositions. Assuming the equality of ΔHtr+(Ph4P+) and ΔHtr+(BPh4), the transfer enthalpies of several ions from water to water-n-propanol mixtures at 298.15 K were calculated.  相似文献   

17.
S Boghosian  G.A Voyiatzis 《Polyhedron》1993,12(24):2965-2971
Raman spectra were obtained at temperatures 375–650 K and pressures up to 4 atm from GaCl3-NbCl5 and GaCl3-TaCl5 binary mixtures in the liquid and vapour state. The data indicate formation of NbGaCl8 and TaGaCl8 liquid and vapour dinuclear addition complexes. The spectra were interpreted in terms of a C configuration for the MGaCl8 (M = Nb, Ta) molecules consisting of a MCl6 octahedron sharing an edge with a GaCl4 tetrahedron. A comparison of the spectral features of 1 : 1 GaCl3-NbCl5 and GaCl3-TaCl5 molten mixtures with the spectra of the corresponding polycrystalline samples indicates that the proposed identity for the complexes is maintained in all three phases. The NbGaCl8 and TaGaCl8 complexes exist in the liquid state in a wide temperature range beyond their melting points (125 and 150°C, respectively) and are shown to undergo dissociation to their components [Nb2Cl10(1)/NbCl5(1), Ga2Cl6(1) and Ta2Cl10(1)/TaCl5(1)] with increasing temperature. Both complex molecules are identified in the gaseous state in low percentages among the vapours of their components and are almost totally decomposed at temperatures higher than ca 325°C. The enthalpy of the reaction TaCl5(g) +1/2Ga2Cl6(g) TaGaCl8(g) was determined from accurate relative Raman intensity measurements as ΔH0 = −38±2 kJ mol−1.  相似文献   

18.
A new optically active ONNO-type tetradentate ligand, ethylenediamine-N,N′- di-S-isobutylacetate (SS-eniba), has been synthesized. During the preparation of diaqua cobalt(III) complexes of SS-eniba, [Co(SS-eniba)(H2O)2]+, the title ligand has coordinated stereospecifically to the cobalt(III) ion to give three isomers, Δ-s-cis, Δ-uns-cis and Λ-uns-cis, which have been isolated and characterized via electronic absorption, circular dichroism (CD), and 1H NMR spectroscopy, along with elemental analysis data. The preparation of Δ-s-cis-[Co(SS-eniba)Cl2]+ and Δ-s-cis-[Co(SS-eniba)CO3]+ are also reported.  相似文献   

19.
Anion exchange membrane has been investigated in different electrolyte solutions by chronopotentiometry to explore the influence of co-ion and counterion of the exchange group of the membrane, on the transport phenomena. Chloride, nitrate, sulfate and acetate in sodium salts were used as counterions and sodium, potassium, calcium and ammonium in chloride salts were used as co-ions. The membrane showed a potential drop (E0) in all these electrolytes when a constant current was applied across it, which remained constant for a period less than τ, called the transition time and rose gradually to a maximum (Emax) value. The parameters such as τ, E0 and Emax and the potential jump (ΔE) and τ and the inflection zone (Δt) along the time axis have been measured and compared at an applied current density (I) of 10 mA cm−2 in 10 mM solutions. The values of τ1/2/zA[A0] or τ1/2/zC[C0], with or , E0 and ΔE with or (where rA and rC are the ionic radii of counter and co-ions, respectively) have been correlated. Permselectivity (P) and transference number of the membrane with respect to each one of the above electrolytes have been evaluated and discussed.  相似文献   

20.
A mixture of NF3 and Ar is passed through an rf discharge in a flow-system to produce, among other species, F and NF2. When H2, D2, or CH4 are added downstream, reactions with F atoms produce vibrationally excited HF or DF together with H, D, or CH3. The latter free radicals can react with NF2, probably by an elimination reaction to produce electronically excited NF: NF2(2B1) + H(D, CH3) → HF*(DF* + NF(a1Δ). A vibrational-to-electronic energy transfer process between the products of this reaction then produces the next higher state of NF: HF(ν 2) + NF(a1Δ) → HF(ν−2) + NF(b1Σ+). A similar transfer process has also been found between the electronically excited a1Δ states of O2 and NF: O2(a1Δ) + NF(a1Δ) → O2(X3Σ) + NF(b1Σ+). The H or D atoms but not the CH3 radicals are then found to react with either NF(a1Δ) or NF(X3Σ) to produce electronically excited N(2D) atoms, which in turn react with the NF(a1Δ) molecules to produce N2(B3Πg). The observed nitrogen first positive radiation has been demonstrated to be produced entirely by this reaction mechanism rather than by the N(4S) recombination that accounts for the Rayleigh afterglow. In addition, the occurrence of the reaction N(2D) + N2O → NO(B2Πr) + N2 (X1Σ+g) has been verified. Finally we have observed emission at 3344 Å, which we attribute to the NF(A3Π), which has not been previously reported.  相似文献   

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