Synthesis, Characterization, and Thermochemical Properties of a

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Synthesis, Characterization, and Thermochemical Properties of a Microporous Crystal Material for Rb2[Ga(B5O10)]·4H2O Sa-Ying Li, Ping Yang, and Zhi-Hong Liu* Key Laboratory for Macromolecular Science of Shaanxi Province, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an 710062, P. R. China ABSTRACT: A new microporous galloborate of Rb2[Ga(B5O10)]·4H2O has been synthesized under mild hydrothermal conditions, which was characterized by chemical analysis, powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR), differential thermal analysis/thermogravimetry (DTA-TG), and single crystal X-ray diffraction. Its structure possesses a 3D open framework with 11-ring channels constructed by B5O10 clusters and GaO4 units. The enthalpies of solution of RbCl(s), KCl(s), K 2 [Ga(B5O10)]·4H2O(s), and Rb2[Ga(B5O10)]·4H2O(s) in the solvents at 298.15 K were measured, respectively. By using the standard molar enthalpies of formation for RbCl(s), KCl(s), and K2[Ga(B5O10)]·4H2O(s), ΔfHmo of Rb2[Ga(B5O10)]·4H2O(s) was obtained as −(5762.9 ± 9.1) kJ·mol−1 on the basis of the appropriate thermochemical cycle. Moreover, ΔfHmo ([Ga(B5O10)]2−) of −(4100.8 ± 9.1) kJ·mol−1 has also estimated by a group contribution method, which can be used to predict the standard molar enthalpies of formation of other galloborates containing the [Ga(B5O10)]2− anionic framework.

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INTRODUCTION Microporous materials have attracted considerable attention due to their widespread applications in catalysis, ion exchange, and adsorption.1 Since the zeolite-like aluminophosphate was discovered,2 other novel inorganic microporous materials with different topological structures have been designed. Because the boron exists as polyborate anions composed of BO3 and BO4 groups, it is expected that the combination of the boron atom and some metal atoms with flexible coordination behaviors in the same compound might produce a new series of materials with novel structures and useful properties. Until now, the boron atom has been introduced in several frameworks of microporous material systems, such as Ge−O−B, Al−O−B, and Ga−O−B.3,4 Thermochemical data of a compound can provide useful information on its stability and reactivity. By using the hightemperature calorimetry, the Navrotsky group has investigated the thermochemistry of some microporous compounds for zeolites, gallosilicate, and aluminophosphates.5,6 Our group has also reported the determination of standard molar enthalpy of formation of the zeolite-like galloborate of K 2 [Ga(B5O10)]·4H2O by using a heat conduction microcalorimeter.7 As part of the continuing study of the Ga−O−B microporous material systems,4,7 this paper reports the synthesis, characterization, and thermochemical properties of a new zeolite-like galloborate for Rb2[Ga(B5O10)]·4H2O.

without further purification. The masses were recorded on an analytical balance (Mettler Toledo XS205 dual range) to a precision of ± 0.1 mg. A mixture of 0.3140 g of Ga2O3 (mass fraction ≥ 0.9999), 2.0120 g of H3BO3 (mass fraction ≥ 0.9950), 1.5220 g of RbOH (mass fraction ≥ 0.9999), 0.0500 g of NH4F (mass fraction ≥ 0.9600), 3.00 cm3 of ethylenediamine (mass fraction ≥ 0.9900), and 3.50 cm3 of doubly distilled water was sealed in a Teflon-lined stainless steel vessels and heated at 443 K for 7 days, then cooled to room temperature. The resulting colorless and transparent crystals were recovered by filtration, washed with deionized water, and dried in a dryer. Characterization. The synthetic sample was characterized by single crystal X-ray diffraction (a colorless, transparent crystal with the dimensions 0.34 × 0.28 × 0.19 mm was selected for the crystal structure measurements by a Bruker Smart-1000 CCD automatic diffractometer with graphitemonochromatized Mo Kα radiation (λ = 0.071073 nm), CSD: 418092), X-ray powder diffraction (Rigaku D/MAX-IIIC X-ray diffractometer with Cu target at 8 deg·min−1), FT-IR spectroscopy (Nicolet NEXUS 670 FT-IR spectrometer by using a KBr pellet at room temperature), and TG-DTA (TASDT Q600 simultaneous thermal analyzer at a heating rate of 10 K·min−1 in flowing N2). The chemical compositions of the sample were determined by NaOH standard solution in the presence of mannitol for B2O3 and by the mass loss in the TG curve for H2O.7

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EXPERIMENTAL SECTION Synthesis of Rb2[Ga(B5O10)]·4H2O. All reagents were of analytical grade and were used as obtained from commercial sources (Sinopharm Chemical Reagent Co., Ltd., China) © 2012 American Chemical Society

Received: January 31, 2012 Accepted: June 19, 2012 Published: June 27, 2012 1964

dx.doi.org/10.1021/je300306x | J. Chem. Eng. Data 2012, 57, 1964−1969

Journal of Chemical & Engineering Data

Article

Calorimetric Experiment. The method for calorimetric experiment is the same as in some of our previous publications.7−10 Rb2[Ga(B5O10)]·4H2O can be regarded as the product of reaction 5 in the designed thermochemical cycle (Figure 1):

Table 1. Crystal Data and Structure Refinement for Rb2[Ga(B5O10)]·4H2O empirical formula formula weight temperature wavelength crystal system, space group unit cell dimensions

K 2[Ga(B5O10 )]·4H 2O(s) + 2RaCl(s) = Rb2 [Ga(B5O10 )]·4H 2O(s) + 2KCl(s)

volume Z, calculated density absorption coefficient F(000) crystal size theta range for data collection limiting indices reflections collected/ unique completeness to theta = 25.49 absorption correction max. and min transmission refinement method data/restraints/ parameters goodness-of-fit on F2 final R indices [I > 2σ(I)] R indices (all data) largest diff. peak and hole

Figure 1. Thermodynamic circle of Rb2[Ga(B5O10)]·4H2O.

The 1 mol·kg−1 HCl(aq) solvent can rapidly dissolve all components of the reaction. All of the enthalpies of solution were measured with an RD496-III heat conduction microcalorimeter (Southwest Institute of Electron Engineering, China), which has been described in detail previously.11,12 The total time required for the complete dissolution reaction was about 0.5 h. There were no solid residues observed after the reactions in each calorimetric experiment. To check the performance of the calorimeter, the mean enthalpy of solution of KCl (mass fraction ≥ 0.9999) in deionized water was determined to be (17.54 ± 0.10) kJ·mol−1 for seven repeat measurements, which was in agreement with that of (17.524 ± 0.028) kJ·mol−1 reported in the literature.13 This shows that the device used for measuring the enthalpy of solution in this work is reliable. In all of these determinations, strict control of the stoichiometries in each step of the calorimetric cycle must be observed, with the objective that the dissolution of the reactants gives the same composition as those of the products in the reaction. Applying Hess’s law, the enthalpy of reaction (5) can be calculated according to the following expression

H8B5GaO14Rb2 526.77 291(2) K 0.71073 Å orthorhombic, C222(1) a = 9.5126(16) Å, α = 90°. b = 10.3814(17) Å, β = 90° c = 13.959(2) Å, γ = 90° 1378.5(4) Å3 4, 2.538 g·cm−3 9.080 mm−1 1000 0.34 mm × 0.28 mm × 0.19 mm 2.90 to 25.49° −11 ⩽ h ⩽ 11, −12 ⩽ k ⩽ 12, −15 ⩽ l ⩽ 16 3520/1270 [R(int) = 0.0159] 99.6 % none 0.2705 and 0.1493 full-matrix least-squares on F2 1270/79/102 1.086 R1 = 0.0539, wR2 = 0.1532 R1 = 0.0549, wR2 = 0.1544 1.235 and −1.579 e·Å−3

Δr Hm o(5) = Δr Hm o(1) + Δr Hm o(2) − Δr Hm o(3) − Δr Hm o(4)

The standard molar enthalpy of formation of Rb2[Ga(B5O10)]·4H2O can be obtained from the value of ΔrHmo (5) in combination with the molar enthalpies of formation of RbCl(s), KCl(s), and K2[Ga(B5O10)]·4H2O(s).

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RESULTS AND DISCUSSION Description of the Structure. Crystal data and conditions of the intensity measurements are given in Table 1. Single crystal X-ray diffraction studies revealed that the crystal structure of title compound is similar to that of reported K2[Ga(B5O10)]·4H2O.4 It consists of two Rb+ cations, one [Ga(B5O10)]2‑ anion, and four lattice water molecules, as shown in Figure 2. The [Ga(B5O10)]2‑ anion is made up of a B5O10 cluster and a GaO4 tetrahedron that are connected through an O atom. The B5O10 cluster consists of two almost planar B3O3 rings linked by a common BO4 tetrahedron, and each ring is

Figure 2. Molecular structure of Rb2[Ga(B5O10)]·4H2O, drawn at the 30 % probability level.

composed of two BO3 triangles (B1, B1A, B2, and B2A) and a slightly distorted common BO4 tetrahedron, which are linked through their vertexes. The B−O distances range from 1.348(12) Å to 1.399(11) Å (av 1.372 Å) and from 1.472(10) Å to 1.478(10) Å (av 1.476 Å), and the O−B−O bond angles are in the ranges of 115.8(8)° to 123.5(8)° and 108.0(10)° to 111.4(3)° for BO3 and BO4 units, respectively. 1965



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the Rb+ cations and lattice water molecules are located and balanced the charge of the [Ga(B5O10)]n2n− framework. The pore size of 10.87 Å × 6.37 Å for Rb2[Ga(B5O10)]·4H2O is slightly bigger than that of 10.594 Å × 5.575 Å for K2[Ga(B5O10)]·4H2O, which is resulted from the relatively bigger radii of the Rb+ cation. The two Rb+ cations are both nine coordinated with five framework O atoms and four bridging water molecules (Figure 4), of which the bridging H2O8 and H2O8A connect the two

The Ga−O distances range from 1.821(6) Å to 1.824(5) Å (av 1.823 Å), and the O−Ga−O bond angles are in the range of 105.2(5)° to 115.8(4)°. The main bond lengths and angles are listed in Table 2. Table 2. Main Bond Lengths (Å) and Angles (deg) of Rb2[Ga(B5O10)]·4H2Oa Ga(1)−O(1)#1 Ga(1)−O(1) Ga(1)−O(4)#2 Ga(1)−O(4)#3 mean

B(3)−O(5)#5 B(3)−O(5) B(3)−O(2) B(3)−O(2)#5 mean

B(1)−O(2) B(1)−O(1) B(1)−O(3) mean B(2)−O(4) B(2)−O(5) B(2)−O(3) mean

Tetrahedral Gallium 1.821(6) O(1)#1−Ga(1)−O(1) 1.821(6) O(1)#1−Ga(1)−O(4)#2 1.824(5) O(1)−Ga(1)−O(4)#2 1.824(5) O(1)#1−Ga(1)−O(4)#3 1.823 O(1)−Ga(1)−O(4)#3 O(4)#2−Ga(1)−O(4)#3 Tetrahedral Boron 1.472(10) O(2)−B(3)−O(2)#5 1.472(10) O(5)#5−B(3)−O(5) 1.478(10) O(5)#5−B(3)−O(2) 1.478(10) O(5)−B(3)−O(2) 1.475 O(5)#5−B(3)−O(2)#5 O(5)−B(3)−O(2)#5 Triangular Boron 1.348(12) O(2)−B(1)−O(1) 1.364(12) O(2)−B(1)−O(3) 1.399(11) O(1)−B(1)−O(3) 1.370 1.353(11) O(4)−B(2)−O(5) 1.378(12) O(4)−B(2)−O(3) 1.389(12) O(5)−B(2)−O(3) 1.373

105.2(5) 108.6(3) 109.0(3) 109.0(3) 108.6(3) 115.8(4) 108.4(10) 108.0(10) 108.8(3) 111.4(3) 111.4(3) 108.8(3) 123.5(8) 120.7(8) 115.8(8)

Figure 4. Coordination environments of Rb+.

119.5(8) 120.5(8) 120.0(8)

pairs of Rb+ ions in two adjacent rings, forming the helical chain structure. The Rb−O distances range from 2.864(9) to 3.480(6) Å (av 3.043 Å). Moreover, there exist weak hydrogen bonds not only between the water molecules (O8−H···O1) but also between the water molecules (H2O6) and the B5O10 cluster O atoms (O5 and O8), with the O···O distances from 2.810(10) Å to 3.167(17) Å and the O−H···O angles from 118.1° to 175.5°. Characterization of the Synthetic Sample. As shown in Figure 5, the diffraction peaks on the powder X-ray diffraction (PXRD) pattern correspond well in position with those of the simulated pattern on the basis of single-crystal structure of Rb2[Ga(B5O10)]·4H2O(s), which indicates that the synthesized sample phase is pure. The FT-IR spectrum of the synthetic sample (Figure 6) is very similar to that of K2[Ga(B5O10)]·4H2O, which exhibited the following absorption bands, and they were assigned referring to the literature.7,14 The peak at 3521 cm−1 is the stretching of O−H. The peak at 1643 cm−1 is the H−O−H bending. The bands at 1359 cm−1 and 938 cm−1 are attributed to the asymmetric and symmetric stretching of B(3)−O, respectively. The bands at 1057 cm−1 and 823 cm−1 are the asymmetric and symmetric bending of B(4)−O. The peak at 631 cm−1 is the out-of-plane bending mode of B(3)-O. The band at 469 cm−1 is the stretching of B(4)−O. The peak at 1243 cm−1 is attributed to Ga(4)−O vibration. These assignments are consistent with its crystal structure. As shown in Figure 7, the thermogravimetric (TG) curve of synthesized sample indicates that the four water molecules in the channel can be removed between (303 and 573) K (found, 13.54 %; calcd, 13.70 %). In the differential thermal analysis (DTA) curve, the three endothermic peaks of (457, 782, and 880) K are related to the dehydration of sample, the

Symmetry transformations used to generate equivalent atoms: #1: x, −y + 2, −z + 1; #2: x − 1/2, −y + 3/2, −z + 1; #3: x − 1/2, y + 1/2, z; #4: −x, y, −z + 3/2; #5: −x + 1, y, −z + 3/2. a

The alternate connectivity between the B5O10 clusters and the GaO4 units through their vertex O atoms gives rise to the 3D macroanionic [Ga(B5O10)]n2n− open framework with 8-ring and 6-ring channels along the [100], [010], and [001] directions, respectively. It is worth noting that there also exists a odd 11-ring channels extending along the crystallographic [110] direction (Figure 3) with the GaO4−BO3−BO4−BO3− GaO4−2(BO3)−GaO4−BO3−BO4−BO3 sequence, in which

Figure 3. Polyhedral view of Rb2[Ga(B5O10)]·4H2O along the [110] direction. 1966



Article

Chemical analytical data for the synthesized sample (calcd/ found, mass fraction): B2O3 (0.3304/0.3282), H2O (0.1370/ 0.1354). The relative standard uncertainty u(r) in the measurements of the mass fraction of each species was estimated to be 0.002. In summary, the results of XRD, TG, and chemical analysis indicate that the synthesized sample is pure and suitable for the calorimetric experiments. Standard Molar Enthalpy of Formation of Rb2[Ga(B5O10)]·4H2O(s). The molar enthalpy of solution of KCl(s) in 2.00 cm3 of 1 mol·kg−1 HCl(aq) at 298.15 K is listed in Table 3. Table 3. Molar Enthalpies of Solution of KCl(s) in the 1 mol·kg−1 HCl(aq) at 298.15 Ka m/mg

no. 1 2 3 4 5 mean

2.30 2.18 2.30 2.42 2.45

± ± ± ± ±

0.01 0.01 0.01 0.01 0.01

ΔrH/mJ 540.7 507.0 539.7 564.4 582.2

± ± ± ± ±

0.1 0.1 0.1 0.1 0.1

ΔsolHm/(kJ·mol−1) 17.53 17.34 17.49 17.39 17.72 17.50

± ± ± ± ± ±

0.08 0.08 0.08 0.08 0.08 0.12b

a

In each experiment, 2.00 cm3 of HCl(aq) was used. bThe uncertainty is estimated as twice the standard deviation of the mean.

Figure 5. X-ray powder diffraction pattern of the synthetic sample.

The molar enthalpy of solution of RbCl(s) in the 2.00 cm3 of 1 mol·kg−1 HCl(aq) at 298.15 K is listed in Table 4. The molar Table 4. Molar Enthalpies of Solution of RbCl(s) in the 1 mol·kg−1 HCl(aq) at 298.15 Ka m/mg

no. 1 2 3 4 5 mean

3.35 3.33 3.41 3.38 3.33

± ± ± ± ±

0.01 0.01 0.01 0.01 0.01

ΔrH/mJ 512.6 513.4 529.9 523.4 501.1

± ± ± ± ±

0.1 0.1 0.1 0.1 0.1

ΔsolHm/(kJ·mol−1) 18.50 18.64 18.79 18.72 18.20 18.57

± ± ± ± ± ±

0.05 0.05 0.05 0.05 0.05 0.16b

a


enthalpy of solution of K2[Ga(B5O10)]·4H2O(s) in the mixture of 2.00 cm3 of 1 mol·kg−1 HCl and the calculated amount of RbCl(s) at 298.15 K is listed in Table 5. The molar enthalpy of solution of Rb2[Ga(B5O10)]·4H2O(s) in the mixture of 2.00 cm3 of 1 mol·kg−1 HCl and calculated amount of KCl(s) at 298.15 K is listed in Table 6. In these tables, m denotes the mass of samples, ΔsolHm denotes the molar enthalpy of solution for solute, and the uncertainty is estimated as twice the

Figure 6. FT-IR spectrum of the synthetic sample.

Table 5. Molar Enthalpies of Solution of Rb2[Ga(B5O10)]·4H2O(s) in the Mixed Solvent of 1 mol·kg−1 HCl(aq) and KCl(aq) at 298.15 Ka no. 1 2 3 4 5 mean

Figure 7. Simultaneous TG-DTA curves of synthetic sample.

m/mg 7.33 7.38 7.50 7.60 7.28

± ± ± ± ±

0.01 0.01 0.01 0.01 0.01

ΔrH/mJ −798.2 −797.0 −815.7 −830.5 −785.9

± ± ± ± ±

0.1 0.1 0.1 0.1 0.1

ΔsolHm/(kJ·mol−1) −57.36 −56.89 −57.29 −57.56 −56.87 −57.19

± ± ± ± ± ±

0.08 0.08 0.08 0.08 0.08 0.27b

a


transformation of polymorph, and the melt of the formed Rb2[Ga(B5O10)], respectively. 1967



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Δf Hm o(Rb2[Ga(B5O10 )]· 4H 2O, s)

Table 6. Molar Enthalpies of Solution of K −1 2[Ga(B5O10)]·4H2O(s) in the Mixed Solvent of 1 mol·kg a HCl(aq) and RbCl(aq) at 298.15 K m/mg

no. 1 2 3 4 5 mean

6.25 6.34 6.28 6.09 6.25

± ± ± ± ±

0.01 0.01 0.01 0.01 0.01

ΔrH/mJ −796.4 −795.5 −793.5 −775.5 −791.6

± ± ± ± ±

0.1 0.1 0.1 0.1 0.1

= 2Δf Hm o(Rb+ , aq) + Δf Hm o([Ga(B5O10 )]2 − , aq) + 4Δf Hm o(H 2O, l)

ΔsolHm/(kJ·mol−1) −55.30 −54.46 −54.84 −55.27 −54.97 −54.97

± ± ± ± ± ±

0.09 0.09 0.09 0.09 0.09 0.31b

where ΔfHmo(K+, aq) = −(252.14 ± 0.08) kJ·mol−1,17 Δ fHmo(Rb+, aq) = −(251.12 ± 0.10) kJ·mol−1,17 and ΔfHmo(H2O, l) = −(290.42) kJ·mol−1.16 Using this scheme, the mean molar enthalpy of formation of [Ga(B5O10)]2− is − (4100.8 ± 9.1) kJ·mol−1. Using this datum, we can predict the standard molar enthalpies of formation of other galloborates containing [Ga(B5O10)]2− anionic framework by a group contribution method.16

a


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standard deviation of the mean, namely, δ = 2(∑(xi − x)̅ 2/n(n − 1))1/2, in which n is experimental number (n = 5); xi, experimental value of each series of repeated measurement; x,̅ mean value. The thermochemical cycle used for the derivation of the standard molar enthalpy of formation of Rb 2 [Ga(B5O10)]·4H2O(s) is given in Table 7. The enthalpy change of reaction (5) was calculated to be (4.36 ± 0.57) kJ·mol−1 on the basis of the thermochemical cycle. The standard molar enthalpies of formation of RbCl (s) and KCl (s) were taken from NBS tables,15 namely, −(435.47 ± 0.10) kJ·mol−1 and −(436.75 ± 0.10) kJ·mol−1. The standard molar enthalpy of formation of K2[Ga(B5O10)]·4H2O(s) of −(5768.5 ± 9.1) kJ·mol−1 was taken from our previous work.7 From these data, the standard molar enthalpy of formation of Rb2[Ga(B5O10)]·4H2O(s) was calculated to be −(5762.9 ± 9.1) kJ·mol−1. The result shows that K2[Ga(B5O10)]·4H2O is slightly more stable than the Rb2[Ga(B5O10)]·4H2O. Estimation of the Thermodynamic Properties by a Group Contribution Method. The molar enthalpy of formation of [Ga(B5O10)]2− can be estimated by a group contribution method,16 which is expressed in the following equation:

CONCLUSIONS

A new zeolite-like galloborate Rb2[Ga(B5O10)]·4H2O has been synthesized. Through an appropriate thermochemical cycle, the ΔfHmo of Rb2[Ga(B5O10)]·4H2O(s) has been obtained. Moreover, the ΔfHmo of [Ga(B5O10)]2− has also estimated by a group contribution method, which can be used to predict the standard molar enthalpies of formation of other galloborates containing a [Ga(B5O10)]2− anionic framework. The comparisons of the title compound with the other related compound of K2[Ga(B5O10)]·4H2O are as follows: (1) Both compounds are isostructural, existing a odd 11-ring channels constructed by B5O10 clusters and GaO4 units, but Rb2[Ga(B5O10)]·4H2O has a slightly bigger pore size. (2) Both compounds have a similar FT-IR spectrum and XRD pattern, respectively, which shows the similar crystal structures. (3) In their DTA curves, the temperature related to the dehydration for K 2 [Ga(B5O10)]·4H2O(460 K) is slightly higher than that of Rb2[Ga(B5O10)]·4H2O(457 K), which shows that the K2[Ga(B 5 O 1 0 )]·4H 2 O(s) is more stable than Rb 2 [Ga(B5O10)]·4H2O(s). (4) The ΔfHmo determined for Rb2[Ga(B5O10)]·4H2O(s) is slightly bigger than that of K2[Ga(B5O10)]·4H2O(s). This result shows that K2[Ga(B5O10)]·4H2O is slightly more stable than Rb2[Ga(B5O10)]·4H2O, which is consistent with their thermal behaviors.

Δf Hm o(K 2[Ga(B5O10 )]·4H 2O, s) = 2Δf Hm o(K+, aq) + Δf Hm o([Ga(B5O10 )]2 − , aq) + 4Δf Hm o(H 2O, l)

Table 7. Thermochemical Cycle and Results for the Derivation of ΔfHmθ Rb2[Ga(B5O10)]·4H2O at 298.15 Ka no. 1

ΔrHθ/(kJ·mol−1)

reaction

37.14 ± 0.32

2RbCl(s) + 144.73(HCl ·54.561H 2O) = 2RbCl(aq) + 144.73(HCl ·54.561H 2O)

2

K 2[Ga(B5O10 )]·4H 2O(s) + 2RbCl(aq) + 144.73(HCl ·54.561H 2O)

−54.97 ± 0.31

= GaCl3(aq) + 2RbCl(aq) + 2KCl(aq) + 139.73(HCl ·56.506H 2O) 3

35.00 ± 0.24

2KCl(s) + 144.73(HCl ·54.561H 2O) = 2KCl(aq) + 144.73(HCl ·54.561H 2O)

4

Rb2 [Ga(B5O10 )]· 4H 2O(s) + 2KCl(aq) + 144.73(HCl ·54.561H 2O)

−57.19 ± 0.27

= GaCl3(aq) + 2RbCl(aq) + 2KCl(aq) + 139.73(HCl ·56.506H 2O) 5

4.36 ± 0.57b

K 2[Ga(B5O10 )]·4H 2O(s) + 2RbCl(s) = Rb2 [Ga(B5O10 )]·4H 2O(s) + 2KCl(s)

ΔfHm°(Rb2[Ga(B5O10)·4H2O,s) = ΔfHm°(5) + ΔfHm°(K2[Ga(B5O10)]·H2O,s) + 2ΔfHm°(RbCl,s) − 2ΔfHm°(KCl,s). bThe uncertainty of the combined reaction is estimated as the square root of the sum of the squares of uncertainty of each individual reaction.

a

1968



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AUTHOR INFORMATION

Corresponding Author

*Tel.: +86-29-81530805; fax: +86-29-81530727. E-mail address: [email protected]. Funding

This project was supported by the National Natural Science Foundation of China (Nos. 20871078 and 21173143) and the Fundamental Research Funds for the Central Universities of China (GK201001005). Notes

The authors declare no competing financial interest.

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REFERENCES

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Synthesis, Characterization, and Thermochemical Properties of a

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