Molar Enthalpies Of Solution Research Articles

Synthesis and thermodynamic properties of 4ZnO·B2O3·H2O with three different morphologies

Polycrystalline 4ZnO·B2O3·H2O with flower-like, spherical-like and sheet-like morphologies have been synthesized and characterized by XRD, TG–DSC, SEM and TEM. The molar enthalpies of solution of 4ZnO·B2O3·H2O with different morphologies in 1 mol L−1 HCl(aq) were measured. With the incorporation of the previously determined enthalpy of solution of H3BO3 in 1 mol L−1 HCl(aq), the enthalpy of solution of ZnO in (HCl + H3BO3)(aq) and the standard molar enthalpies of formation of ZnO(s), H3BO3(s) and H2O(l), the standard molar enthalpies of formation of 4ZnO·B2O3·H2O with flower-like, spherical-like, and sheet-like morphologies were calculated to be -(3033.91 ± 2.03), -(3030.91 ± 2.03) and -(3025.94 ± 2.04) kJ·mol−1, respectively.

Equilibria of the ternary systems CsBr–LnBr3 (Ln = Gd, Dy)–H2O and the quaternary system CsBr–GdBr3–HBr (∼12.1 mass %)–H2O at T = 298.15 K and standard molar enthalpies of formation for new compounds

As part of a series of studies, this paper reports experimental phase equilibrium data for CsBr–GdBr3–H2O, CsBr–DyBr3–H2O and CsBr–GdBr3–HBr (∼12.1 mass %)–H2O systems at T = 298.15 K. The phase diagrams were constructed based on the measured data. In the phase diagrams of the ternary system CsBr–GdBr3–H2O and the quaternary system CsBr–GdBr3–HBr (∼12.1 mass %)–H2O,there are all two invariant points, and three crystallization regions corresponding to CsBr, Cs3GdBr6·10H2O, and GdBr3·6H2O, respectively.There are two invariant points and three crystallization regions corresponding to CsBr, Cs3Dy2Br9·16H2O and DyBr3·6H2Oin the system CsBr–DyBr3–H2O.The experimental solubility values of gadolinium bromide and dysprosium bromide at 298.15 K were 65.42 mass % and 65.94 mass %. The compounds Cs3GdBr6·10H2O and Cs3Dy2Br9·16H2O are incongruently soluble in water or a medium of ∼ 12.1 mass % HBr, and were characterized by XRD and TG-DTG techniques. The standard molar enthalpies of solution for Cs3GdBr6·10H2O, Cs3Dy2Br9·16H2O, GdBr3·nH2O (n = 6.00) and DyBr3·nH2O (n = 5.99) were obtainedby means of microcalorimetric measurement, the values found for standard molar enthalpies of formation of Cs3GdBr6·10H2O, Cs3Dy2Br9·16H2O, GdBr3·nH2O (n = 6.00) and DyBr3·nH2O (n = 5.99) were – (5104.8 ± 3.2) kJ·mol−1, – (7827.3 ± 3.6) kJ·mol−1, – (2726.0 ± 2.7) kJ·mol−1 and – (2734.5 ± 3.3) kJ·mol−1, respectively.

Dilution enthalpies of the binary systems (LiBO2 + H2O) and (LiB5O8 + H2O) and the ion interactions at 308.15 K

Microcalorimeter measured the dilution enthalpies of the binary systems (LiBO2 + H2O) and (LiB5O8 + H2O) at 308.15 K and 0.1 MPa. Based on the Pitzer theory of electrolytes, their apparent molar enthalpies and the Pitzer single electrolyte parameters at 308.15 K were carried out by fitting the experimental data for the first time. Moreover, the calculated apparent molar enthalpies of LiBO2 and LiB5O8 aqueous solution according to the Pitzer ion-interaction model were consistent well with the experimental values, manifesting the high reliability of this study.

Energetics of dehydroepiandrosterone polymorphs I and II from solution and drop-sublimation Calvet microcalorimetry measurements

The lattice enthalpies and monotropic relationship of two dehydroepiandrosterone (DEHA) polymorphs (forms I and II) were evaluated through a combination of differential scanning calorimetry (DSC), isothermal solution microcalorimetry, and drop-sublimation Calvet microcalorimetry experiments. The standard molar enthalpy of transition between both forms was determined as ΔtrsHmo(II→I, 298.15 K) = −0.90 ± 0.07 kJ mol−1 and ΔtrsHmo(II→I, 417.8 K) = −1.7 ± 1.0 kJ mol−1, from measurements of standard molar enthalpies of solution in dimethyl sulfoxide and enthalpies of fusion, respectively. Drop-sublimation Calvet microcalorimetry experiments on form I led to ΔsubHmo(cr I, 298.15 K) = 132.0±3.3 kJ mol−1. This result, when combined with the more precise ΔtrsHmo(II→I) value obtained by solution calorimetry, afforded ΔsubHmo(cr II, 298.15 K) = 131.1±3.3 kJ mol−1. The overall data indicate that on enthalpic grounds form I is more stable than form II from 298.15 K up to fusion. This conclusion, and the fact that DSC experiments indicated that form I has also a considerably higher temperature fusion, namely, Tfus(cr I)= 422.5±0.2 K and Tfus(cr II) = 413.1±0.2 K, suggest that the two polymorphs are monotropically related.

Composition of the Solvation Shell of the Selected Cyclic Ethers (1,4-Dioxane, 12-Crown-4, 15-Crown-5 and 18-Crown-6) in a Mixture of Formamide with Water at Four Temperatures

The solution enthalpy of 15-crown-5 and 18-crown-6 ethers in the mixture of formamide (F) and water (W) was measured at four temperatures: 293.15 K, 298.15 K, 303.15 K, 308.15 K. The standard molar enthalpy of solution, ΔsolHo, depends on the size of cyclic ethers molecules and the temperature. With increasing temperature, the values of ΔsolHo become less negative. The values of the standard partial molar heat capacity Cp,2o of cyclic ethers at 298.15 K have been calculated. The Cp,2o=f(xW) curve shape indicates the hydrophobic hydration process of cyclic ethers in the range of a high-water content in the mixture with formamide. The enthalpic effect of preferential solvation of cyclic ethers was calculated and the effect of temperature on the preferential solvation process was discussed. The process of complex formation between 18C6 molecules and formamide molecules is observed. The cyclic ethers molecules are preferentially solvated by formamide molecules. The mole fraction of formamide in the solvation sphere of cyclic ethers has been calculated.

Two Ternary Systems of MnCl2 + Glycine (l-Proline) + H2O at 298.15 K and the Standard Molar Enthalpy of Formation of Their Double Salts

Two phase diagrams of MnCl2 + glycine (l-proline) + H2O at 298.15 K have been drawn. Three double salts of Mn(C2H5NO2)Cl2·2H2O, Mn(C2H5NO2)2Cl2, and Mn(C5H9NO2)Cl2·H2O are prepared in aqueous solution and they are all congruently soluble in water. Their thermal properties are studied by thermogravimetry and differential thermogravimetry (TG–DTG) and their structure information is obtained by powder X-ray diffraction. By means of the molar enthalpies of solution of Mn(C2H5NO2)Cl2·2H2O, Mn(C2H5NO2)2Cl2, and Mn(C5H9NO2)Cl2·H2O and the thermochemical cycles (based on Hess law), standard molar enthalpies of the formation of Mn(C2H5NO2)Cl2·2H2O (−1642.50 ± 1.08 kJ·mol–1), Mn(C2H5NO2)2Cl2 (−1582.4 ± 1.12 kJ·mol–1), and Mn(C5H9NO2)Cl2·H2O (−1336.97 ± 2.30 kJ·mol–1) at 298.15 K have been obtained.

Solubility Phase Diagrams of ternary systems of CsCl–CdCl2–H2O and CsBr–CdBr2–H2O at T = 298.1 K and the thermodynamic properties of the new solid phase compounds

Using an isothermal equilibrium method, thephaseequilibrium of the ternary systems CsCl–CdCl2–H2O and CsBr–CdBr2–H2O were studied at T = 298.1 K. In thephasediagram of the system CsCl–CdCl2–H2O, the solidphasesof CsCdCl3 and Cs2CdCl4, besides CsCl and CdCl2·2.5H2O, were discovered. Thephasediagramof the system CsBr–CdBr2–H2O contains five crystallization fields for the solidphases CdBr2·4H2O, CsCdBr3, Cs5Cd2Br9, Cs3CdBr5 and CsBr. The new solidphasesof CsCdCl3 and CsCdBr3 are congruently soluble, and Cs2CdCl4, Cs5Cd2Br9 and Cs3CdBr5 are incongruently soluble in the aqueous system. The experimental solubility data and phase diagrams for the ternary systems show more practical application for the obtained cadmium-based halide perovskite. The five new solid phase have been analyzed by X-ray diffraction and thermogravimetry/derivative thermogravimetry. By measuring the standard molar enthalpies of solution of the compounds, the standard molar enthalpies of formation of CsCdCl3, Cs2CdCl4, CsCdBr3, Cs5Cd2Br9, Cs3CdBr5 were determined to be –(873.3 ± 0.7) kJ·mol−1, –(1325.6 ± 0.9) kJ·mol−1, –(742.8 ± 0.7) kJ·mol−1, –(2710.0 ± 1.3) kJ·mol−1 and –(1558.1 ± 1.0) kJ·mol−1, respectively.

Solid–liquid equilibria in the systems cesium bromide + holmium bromide + water and cesium bromide + holmium bromide + hydrobromic acid (~11.7 mass %) + water at T = 298.15 K

The (Solid–Liquid) phase equilibria for the systems of cesium bromide + holmium bromide + water and cesium bromide + holmium bromide + hydrobromic acid (~11.7 mass %) + water at T = 298.15 K were researched by the isothermal dissolution equilibrium method. According to the experimental data, the phase diagrams of the two systems were depicted. There were two invariant points, three invariant curves, and three crystallization fields (CsBr, Cs3Ho2Br9·16H2O, HoBr3·8H2O) in the two phase diagrams. Cs3Ho2Br9·16H2O was incongruently soluble in the two systems. The solubility of HoBr3 measured in water at T = 298.15 K is 65.41 mass %. The compound Cs3Ho2Br9·16H2O was investigated using chemical analysis, XRD and TG-DTG analysis. The standard molar enthalpy of solution of Cs3Ho2Br9·16H2O in water was measured to be −(5.54 ± 0.28) kJ/mol by a microcalorimetry, and its standard molar enthalpy of formation was determined as being –(7846.5 ± 1.2) kJ/mol.

Construction and performance evaluation of a CSC-1 type horizontal rotating micro-bomb combustion-solution isoperibol multifunctional calorimeter

In this work, a CSC-1 type horizontal rotating micro-bomb combustion-solution isoperibol multifunctional calorimeter was constructed. There are three main differences between the structure of this calorimeter and the existing calorimeters: (1) two functions, i.e. the measurements of combustion heat and solution heat were integrated together; (2) Dewar bottle was used as a shared calorimetric container for the determination of combustion heat and solution heat; (3) submersible magnetic mixer replaced the traditional mechanical rod mixer. The energy equivalent of combustion system in the calorimeter was calibrated with NIST SRM 39j benzoic acid, giving the result of (1181.94 ± 0.23) J⋅K−1. Furthermore, the standard specific energy of combustion of salicylic acid was measured using the combustion system, and the result showed that the standard specific energy of combustion of salicylic acid was – (21884.9 ± 5.4) J·g−1 at 298.15 K. Then, the standard molar enthalpy of formation of salicylic acid was calculated to be ΔfHmo[C7H6O3(s),298.15K]=-(589.27±2.98)kJ⋅mol−1. In addition, the energy equivalent of solution system in the calorimeter was calibrated with electrical energy, giving the result of (5.28084 ± 0.00261) J·mV−1. And the standard specific enthalpy of solution of KCl was measured by the solution system in water at 298.15 K, the results indicated that the standard specific and molar enthalpy of solution of KCl (1100 H2O, 298.15 K) were (235.33 ± 0.03) J·g−l and (17543.2 ± 8.9) J·mol−l, respectively. All these results demonstrated that the calorimetric systems of combustion and solution in the developed calorimeter are reliable and feasible.

Standard molar enthalpy of the orthorhombic to monoclinic polymorphic phase transition in 4′-hydroxyacetophenone from enthalpy of solution measurements

The standard molar enthalpy of transition between the two known polymorphs of 4′-hydroxyacetophenone (HAP), at 298.15 K, was determined from measurements of their standard molar enthalpies of solution in dimethyl sulfoxide (DMSO). The obtained result ΔtrsHmo(cr II→cr I) = (0.48 ± 0.10) kJ.mol−1 is in excellent agreement with a previously reported value measured in ethanol with an isoperibol calorimeter, using ~ 7 times larger amounts of sample and solvent. The fact that the two polymorphs are easily prepared, and such good agreement was observed between results from two considerably different calorimetric techniques and solvents, suggests that HAP may be a convenient benchmark system for the validation of solution calorimetry measurements or force field predictions on the relative enthalpic stability of organic polymorphs.

Thermodynamic properties for two mixed alkaline earth-transition metal borates of BaZn2B2O6 and Ba2Cd(B3O6)2

Two alkaline-earth metal borates BaZn2B2O6 with NLO property and Ba2Cd(B3O6)2 with birefringent property have been synthesized and characterized by XRD, FT-IR, and chemical analysis. The molar enthalpies of solution of BaZn2B2O6 (s) and Ba2Cd(B3O6)2(s) in 2.00 mL of 1 mol·dm−3 HCl(aq) were measured by microcalorimeter at T = 298.15 K, respectively. The molar enthalpies of solution of CdCl2·2.5H2O(s) and ZnO(s) in the mixture solvent of 2.00 mL of {1 mol·dm–3HCl + H3BO3 + Ba(OH)2·8H2O} (aq) were also measured, respectively. With the incorporation of the previously determined enthalpies of solution of H3BO3 (s) in 2.00 mL of 1 mol· dm–3HCl (aq), Ba(OH)2·8H2O) in the mixture solvent of (2.00 mL of 1 mol·dm−3 HCl + H3BO3) (aq), together with the standard molar enthalpies of formation for CdCl2·2.5H2O(s)/ZnO(s), Ba(OH)2·8H2O(s), H3BO3(s), HCl (aq) and H2O (l), the standard molar enthalpies of formation of – (2703.0 ± 2.2) kJ·mol−1 for BaZn2B2O6 (s) and – (5625.26 ± 5.1) kJ·mol−1 for Ba2Cd(B3O6)2 at T = 298.15 K were obtained on the basis of the appropriate thermochemical cycles.

Synthesis, characterization and standard molar enthalpies of formation of two zinc borates: 2ZnO·2B2O3·3H2O and ZnB4O7

The standard mole enthalpy of formation is an essential feature of chemical compounds, which is critical for assessing the thermal effects of chemical reactions with their participation. In this paper, two pure phases of zinc borates, 2ZnO·2B2O3·3H2O and ZnB4O7, have been synthesized by hydrothermal and boric acid flux methods, respectively. They were characterized by XRD, FT-IR and TGA. The molar enthalpies of solution of 2ZnO·2B2O3·3H2O (s) and ZnB4O7 (s) in 1 mol·dm−3 HCl (aq) were measured at T = 298.15 K, respectively, by the use of an isothermal microcalorimeter. In accordance with Hess’ law, the standard molar enthalpies of formation of the two zinc borates 2ZnO·2B2O3·3H2O (s) and ZnB4O7 (s) were calculated to be −(4177.02 ± 3.3) kJ·mol−1 and −(2971.1 ± 3.3) kJ·mol−1, respectively, by the use of standard molar enthalpies of formation for ZnO (s), H3BO3 (s) and H2O (l) based on the two designed thermochemical cycles.

Solution enthalpy of ionic liquids [C<sub><italic>n</italic></sub>Py][HSO<sub>4</sub>](<italic>n</italic>=2, 3, 4, 5, 6)

<p indent="0mm">Ionic liquids are known as environmentally friendly solvents in the 21st century, and they have become one kind of the most attractive soft materials in industry and academic communities. The thermodynamic data of ionic liquid are important parameters in the industry. It is crucial to obtain thermodynamic data for the application of the ILs in the industry and technological design. However, it has become a big obstacle to the industrialization of ionic liquids due to the lack of foundation data. In this article, five acidic pyridine-based ionic liquids [C_{<italic>n</italic>}Py][HSO₄](<italic>n</italic>=2, 3, 4, 5, 6) were synthesized by using the neutralization method and characterized by ¹H NMR spectrum. The molar solution enthalpies were measured by using a SRC100 type calorimeter, which the calorimeter was verified by standard material KCl, solution enthalpies at different molalities of five kinds of ILs [C_{<italic>n</italic>}Py][HSO₄](<italic>n</italic>=2, 3, 4, 5, 6) were also determined, and the molar solution enthalpies at the infinite dilution and relative parameters were also obtained by application of Pitzer’s equation.

Phase equilibria in Mg(NO3)2–Ln(NO3)3 (Ln = Nd, Sm, Eu, Tb)–HNO3 (∼20%)–H2O systems at 298.15 K and thermodynamic properties of Mg3Ln2(NO3)12·24H2O (Ln = Nd, Sm)

The phase diagrams of the Mg(NO3)2–Ln(NO3)3 (Ln = Nd, Sm, Eu, Tb)–HNO3–H2O systems in the (∼20%) HNO3 regions at T = 298.15 K were determined by using an isothermal solution saturation method. The Schreinemaker’s wet residues method was used to determine the compositions of solid-phases. Both Mg(NO3)2–Nd(NO3)3–HNO3–H2O and Mg(NO3)2–Sm(NO3)3–HNO3–H2O systems are complicated with three equilibrium solid phases Mg(NO3)2·6H2O, Mg3Ln2(NO3)12·24H2O and Ln(NO3)3·6H2O (Ln = Nd, Sm). But the systems Mg(NO3)2–Eu(NO3)3–HNO3–H2O and Mg(NO3)2–Tb(NO3)3Tb–HNO3–H2O are simple eutonic type. The two new solid-phase compounds Mg3Nd2(NO3)12·24H2O and Mg3Sm2(NO3)12·24H2O are congruently soluble in an average medium of ∼20 mass % HNO3, and they were identified and characterized by the methods of powder X-ray diffraction, X–ray diffraction single crystal structure analysis, and thermogravimetric/differential thermogravimetric. The XRD diffraction patterns for the two new solid-phase compounds are identical due to their isomorphic structure. They belong to hexagonal systems, with space group R3. For Mg3Nd2(NO3)12·24H2O, a = b = (1.0993 ± 0.0005) nm, c = (1.7211 ± 0.0007) nm, V = (1.8012 ± 0.0013) nm3, Dc = (4.2532 ± 0.0024) g·cm−3, Z = 3; for Mg3Sm2(NO3)12·24H2O, (a = b = 1.1198 ± 0.0004) nm, c = (1.7257 ± 0.0006) nm, V = (1.8742 ± 0.0011) nm3, Dc = (4.1201 ± 0.0012) g cm−3, Z = 3. The standard molar enthalpies of solution of the compounds Mg3Nd2(NO3)12·24H2O and Mg3Sm2(NO3)12·24H2O in water (aq) were measured to be (101.26 ± 0.77) kJ mol−1 and (80.27 ± 0.81) kJ mol−1, and their standard molar enthalpies of formation were calculated to be – (12214.13 ± 2.5) kJ mol−1 and – (12183.6 ± 2.5) kJ mol−1, respectively.

Thermochemical properties of alkaline-earth metals borates of a series of MB8O11(OH)4·xH2O (M = Ca, Sr, Ba; x = 0, 3)

A pure barium borate of BaB8O11(OH)4·3H2O has been synthesized and characterized by XRD, FT-IR, TGA, and chemical analysis. The molar enthalpies of solution of BaB8O11(OH)4·3H2O in 1 mol dm−3 HCl(aq), and Ba(OH)2·8H2O in the mixture solvent of {2.00 cm3 of 1 mol·dm−3 HCl + H3BO3(aq)} were measured by microcalorimeter at T = 298.15 K, respectively. With the use of previously determined enthalpy of solution of H3BO3 (s) in 1 mol·dm−3 HCl(aq), and the standard molar enthalpies of formation for Ba(OH)2·8H2O(s), H3BO3(s), and H2O(l), the standard molar enthalpy of formation of −(7500.6 ± 6.5) kJ·mol−1 at T = 298.15 K was obtained based on an appropriate thermochemical cycle. Moreover, the molar enthalpy of formation of −6091.7 kJ mol−1 for [B8O11(OH)4]2− was estimated by a group contribution method, which was used to predict the ΔfHmo of a series of alkaline-earth metal borates for MB8O11(OH)4 (M = Ca, Sr, Ba).

Solid-liquid equilibria for the systems of (CsCl + DyCl3 + H2O) and {CsCl + DyCl3 + HCl (∼10.7%) + H2O} at T = 298.15 K and the thermodynamic properties of the new solid compounds

Solid–liquid equilibria in the ternary system (CsCl + DyCl3 + H2O) and the quaternary system {(CsCl + DyCl3 + HCl (∼10.7%) + H2O} at T = 298.15 K and under 101.3 kPa were investigated by the method of isothermal solution saturation, and the corresponding phase diagrams were constructed. It was found that there were three crystallization regions corresponding to CsCl, Cs2DyCl5·6H2O and DyCl3·6H2O in the ternary system. Nevertheless, four crystallization regions corresponding to CsCl, Cs5DyCl8·6H2O, Cs2DyCl5·6H2O and DyCl3·6H2O were found in the quaternary system. The compound Cs2DyCl5·6H2O was congruently soluble in the two systems, and new double salt Cs5DyCl8·6H2O was formed in the quaternary system which was congruently soluble in an average medium of ∼10.7 mass% HCl. The new solid-phase compounds Cs5DyCl8·6H2O and Cs2DyCl5·6H2O were characterized by chemical analysis, XRD and TG-DTG techniques. The standard molar enthalpies of solution of Cs5DyCl8·6H2O and Cs2DyCl5·6H2O in water were measured to be (44.28 ± 0.50) kJ·mol−1 and (5.32 ± 0.27) kJ·mol−1 by microcalorimetry in the condition of infinite dilution, and their standard molar enthalpies of formation were determined to be –(5086.9 ± 1.3) kJ·mol−1 and –(3771.6 ± 0.9) kJ·mol−1. As part of this work, five compounds Cs3LaCl6·3H2O, CsLaCl4·4H2O, CsCeCl4·4H2O, CsPrCl4·6H2O and CsNdCl4·9H2O were synthesized according to the literature [18–21]. The molar enthalpies of solution of Cs3LaCl6·3H2O, CsLaCl4·4H2O, CsCeCl4·4H2O, CsPrCl4·6H2O and CsNdCl4·9H2O in water were also measured to be (14.78 ± 0.31) kJ·mol−1, –(30.98 ± 0.62) kJ·mol−1, –(20.26 ± 0.22) kJ·mol−1, –(19.64 ± 0.54) kJ·mol−1 and –(5.86 ± 0.45) kJ·mol−1 in the condition of infinite dilution, and their standard molar enthalpies of formation were calculated to be –(3351.1 ± 1.1) kJ·mol−1, –(2740.3 ± 1.0) kJ·mol−1, –(2746.1 ± 0.7) kJ·mol−1, –(3326.8 ± 0.9) kJ·mol−1 and –(4189.7 ± 0.9) kJ·mol−1, respectively.

The enthalpies of formation for various Cu–Li–Sb compounds

The system Cu–Li–Sb has recently gained much attention with regard to Cu–Sb alloys being used as electrode materials for lithium ion batteries. Only few data exists however on the thermodynamics governing the lithiation of such electrode materials. A theoretical model of the corresponding phase diagrams, as provided by the CALPHAD approach, would give tremendous insights, not only into the thermodynamics but also to certain kinetic aspects governing these materials. However in order to develop a reliable model, fundamental experimental data is necessary. Especially the Gibbs energies and enthalpies of formation for the encountered intermetallic phases are essential building blocks for modeling of the system.In this work, the enthalpies of formation of four ternary compounds, i.e. CuLi2−xSb, Cu2−xLi1−xSb, Cu1.5−xLi1+xSb, Cu4+xLi1−xSb2 (i.e. T1–T4), were determined by two different experimental methods. Drop solution calorimetry using a tin bath was used to derive the enthalpies of formation from the limiting partial molar enthalpies of solution of the different ternary compounds as well as of their constituent components. Emf measurements at temperatures ranging from 642 K to 754 K were applied to calculate the enthalpies of formation from the integrated partial enthalpies of reaction with respect to liquid lithium. An electrochemical cell which can be represented as W|”Al, LiAl”|LiCl–KCl|CuxLiySbz|W was used for these measurements.

Thermodynamic properties for two mixed alkali-transition metal borates of Li6Zn3B4O12 and Na3ZnB5O10

Abstract Two pure mixed alkali-transition metal borates, Li6Zn3B4O12(s) and Na3ZnB5O10(s) have been synthesized and characterized by XRD, FT-IR, and chemical analysis. For Li6Zn3B4O12, the molar enthalpy of solution of Li6Zn3B4O12 in the mixture solvent of {2.00 mL of 1 mol·L−1 HCl + H3BO3)(aq)} was measured. The molar enthalpies of solution of ZnO(s) in 1 mol·L−1 HCl(aq), and LiBO2(s) in the mixture solvent of {2.00 mL of 1 mol·L−1 HCl(aq) + ZnO(aq)} were also measured. For Na3ZnB5O10, the molar enthalpy of solution of Na3ZnB5O10 in 2.00 mL of 1 mol·L−1 HCl(aq) was measured. The molar enthalpy of solution of NaBO2·4H2O(s) in the mixture solvent of {2.00 mL of 1 mol·L−1 HCl(aq) + H3BO3 + ZnO](aq)} was also measured. With the incorporation of the previously determined enthalpy of solution of H3BO3 (s) in 1 mol·L−1 HCl(aq), and ZnO(s) in {1 mol·L−1 HCl(aq) + H3BO3}, together with the use of the standard molar enthalpies of formation for LiBO2(s)/NaBO2·4H2O(s), ZnO(s), H3BO3(s) and H2O(l), the standard molar enthalpies of formation of −(5867.5 ± 4.8) kJ·mol−1 for Li6Zn3B4O12 and −(4655.3 ± 6.6) kJ·mol−1 for Na3ZnB5O10 at T = 298.15 K were obtained on the basis of two appropriate thermochemical cycles.

Thermochemical properties of two mixed alkali-alkaline earth metal borates with NLO properties for NaCaBO 3 and Li 4 CaB 2 O 6

Abstract Two alkali-alkaline earth metal borates with NLO properties for NaCaBO3 and Li4CaB2O6 have been synthesized and characterized by XRD, FT-IR, and chemical analysis. The molar enthalpies of solution of NaCaBO3 (s) and Li4CaB2O6 (s) in 2.00 cm3 of 1 mol·dm−3 HCl (aq) were measured by microcalorimeter at T = 298.15 K, respectively. The molar enthalpies of solution of CaCl2·2H2O(s) in the mixture solvent of 2.00 cm3 of (1 mol·dm−3 HCl + H3BO3 + NaCl) (aq), and {2.00 cm3 of 1 mol·dm−3 HCl + H3BO3 + LiCl·H2O} (aq) were also measured, respectively. With the incorporation of the previously determined enthalpies of solution of H3BO3 (s) in 2.00 cm3 of 1 mol·dm−3 HCl (aq), NaCl (s) in the mixture solvent of (2.00 cm3 of 1 mol·dm−3 HCl + H3BO3) (aq) and LiCl·H2O(s) in the mixture solvent of {2.00 cm3 of 1 mol·dm−3 HCl + H3BO3} (aq), together with the standard molar enthalpies of formation for CaCl2·2H2O (s), NaCl(s)/LiCl·H2O (s), H3BO3 (s), HCl (aq) and H2O (l), the standard molar enthalpies of formation of – (1664.5 ± 0.9) kJ·mol−1 for NaCaBO3 (s) and – (3391.7 ± 1.9) kJ·mol−1 for Li4CaB2O6 (s) at T = 298.15 K were obtained on the basis of the appropriate thermochemical cycles.

Molecular Aggregation in Binary Mixtures of Pyrrolidine, N-Methylpyrrolidine, Piperidine, and N-Methylpiperidine with Water: Thermodynamic, SANS, and Theoretical Studies.

Piperidine and N-methylpiperidine hydrates aggregate in liquid aqueous solutions due to hydrogen bonds between hydration water molecules. No such effects occur in the mixtures of the amines with methanol, that supports the idea of active role of water solvent in the aggregation. However, the question of contributions in thermodynamic functions due to specific interactions, van der Waals forces, and the size and shape of the molecules remains open. In the present study, limiting partial molar enthalpies of solution of pyrrolidine, N-methylpyrrolidine, piperidine, and N-methylpiperidine in water and methanol and vice versa were measured and compared with those assessed from theoretically calculated molecular interaction energies using a simple "chemical reaction" model. Nearly quantitative agreement of the enthalpies was achieved for the systems studied, except the amines in water. The latter required an empirical hydrophobic hydration term to be considered. The hydrogen bonds formation and breaking which accompany the mixtures formation leads to considerable excess volumes, while the size of the solute molecules is manifested rather in the compressibility of aqueous solutions. SANS evidenced that aqueous solutions are microheterogeneous on the nanometer-order length scale. The propensity to promote phase separation increases in the order: N-methylpiperidine < N-methylpyrrolidine < piperidine < pyrrolidine.