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1.
Calorimetric measurements of the enthalpy of solution of cesium chromate gave ΔHsoln = (7622 ± 24) cal th mol ?1 for a dilution of Cs 2CrO 4·21128H 2O. This result, along with the enthalpy of dilution gave the standard enthalpy of solution, ΔHsolno = (7512 ± 31) cal th mol ?1, whence the standard enthalpy of formation, ΔHf0(Cs 2CrO 4, c, 298.15 K), was calculated to be ?(341.78 ± 0.46) kcal th mol ?1. Recomputed thermodynamic data for the formation of the other alkali metal chromates have been tabulated. From their solubilities and enthalpies of solution, the standard entropies, S0(298 K), of BaCrO 4 and PbCrO 4 were estimated to be (38.9 ± 0.9) and (43.7 ± 1.2) cal th K ?1 mol ?1, respectively. There is evidence that ΔHf0(SrCrO 4, c, 298.15 K) may be in error. Thermochemical, solubility, and equilibrium data, have been combined to update the thermodynamic properties of the aqueous chromate (CrO 42?), bichromate (HCrO 4?), and dichromate (Cr 2O 72?) ions. The new values at 298.15 K are as follows: | | | | CrO42?(aq) | (13.8 ± 0.5) | ?(210.93 ± 0.45) | ?(174.8 ± 0.5) | HCrO4?(aq) | (46.6 ± 1.8) | ?(210.0 ± 0.7) | ?(183.7 ± 0.5) | Cr2O72?(aq) | (67.4 ± 3.9) | ?(356.5 ± 1.5) | ?(312.8 ± 1.0) | 相似文献
2.
The standard enthalpy of formation of γ-UO 3 has been critically assessed; the value ?(292.5 ± 0.2) kcal th mol ?1 is suggested.The enthalpies of solution of β-UO 3 and γ-UO 3 in 3 M H 2SO 4 have been measured and used to derive: 相似文献
3.
Enthalpies of reaction, ΔHr, of the monouranates of lithium, potassium, and rubidium with 1 mol dm ?3 HCl have been measured calorimetrically. From these measurements, and auxiliary determinations of the enthalpies of solution in acid of the chlorides of lithium, potassium, and rubidium and of uranyl chloride, the standard enthalpies of formation of the uranates, ΔHfo, have been derived. The results obtained are as follows: | | | α-Li2UO4 | ?(41.77±0.02) | ?(463.31±0.84) | K2UO4 | ?(42.07±0.05) | ?(451.39±0.83) | Rb2UO4 | ?(41.30±0.05) | ?(452.00±0.85) | 相似文献
4.
The heat capacity of a sample of Cs 2CrO 4 was determined in the temperature range 5 to 350 K by aneroid adiabatic calorimetry. The heat capacity at constant pressure Cpo(298.15 K), the entropy So(298.15 K), the enthalpy { Ho(298.15 K) - Ho(0)} and the function were found to be (146.06 ± 0.15) J K ?1 mol ?1, (228.59 ± 0.23) J K ?1 mol ?1, (30161 ± 30) J mol ?1, and (127.43 ± 0.13) J K ?1 mol ?1, respectively. The heat capacity Cpo(298.15 K) and entropy So(298.15 K) and entropy So(298.15 K) of Rb 2CrO 4 are estimated to be (146.0 ± 1.0) J K ?1 mol ?1 and (217.6 ± 3.0) J K ?1 mol ?1, respectively. 相似文献
5.
The heat capacities of potassium, rubidium, cesium, and thallium azides were determined from 5 to 350 K by adiabatic calorimetry. Although the alkali-metal azides studied in this work exhibited no thermal anomalies over the temperature range studied, thallium azide has a bifurcated anomaly with two maxima at (233.0±0.1) K and (242.04±0.02) K. The associated excess entropy was 0.90 cal th K ?1 mol ?1. The thermal properties of the azides and the corresponding structurally similar hydrogen difluorides are nearly identical. Both have linear symmetrical anions. However, thallium azide shows a solid-solid phase transition not exhibited by thallium hydrogen difluoride. At 298.15 K the values of Cpo, So, and , respectively, are 18.38, 24.86, and 12.676 cal th K ?1 mol ?1 for potassium azide; 19.09, 28.78, and 15.58 cal th K ?1 mol ?1 for rubidium azide; 19.89, 32.11, and 18.17 cal th K ?1 mol ?1 for cesium azide; and 19.26, 32.09, and 18.69 cal th K ?1 mol ?1 for thallium azide. Heat capacities at constant volume for KN 3 were deduced from infrared and Raman data. 相似文献
6.
The mutual solubilities of { xCH 3CH 2CH 2CH 2OH+(1- x)H 2O} have been determined over the temperature range 302.95 to 397.75 K at pressures up to 2450 atm. An increase in temperature and pressure results in a contraction of the immiscibility region. The results obtained for the critical solution properties are: To(U.C.S.T.) = 397.85 K and xo = 0.110 at 1 atm; at p < 400 atm and at 800 atm < p < 2500 atm; . 相似文献
7.
The energies of reaction of XeF 6(c), XeF 4(c), and XeF 2(c) with PF 3(g) were measured in a bomb calorimeter. These results were combined with the enthalpy of fluorination of PF 3(g), which was redetermined to be −(151.98 ± 0.07) kcal th mol −1, to derive (at 298.15 K) ΔHfo(XeF 6, c, I) = −(80.82 ± 0.53) kcal th mol −1, ΔHfo(XeF 4, c) = −(63.84 ± 0.21) kcal th mol −1, and ΔHfo(XeF 2, c) = −(38.90 ± 0.21) kcal th mol −1. The enthalpies of formation of the solid xenon fluorides were combined with reported enthalpies of sublimation to derive (at 298.15 K) ΔHfo(XeF 6, g) = −(66.69 ± 0.61) kcal th mol −1, ΔHfo(XeF 4, g) = −(49.28 ± 0.22) kcal th mol −1, and ΔHfo(XeF 2, g) = −(25.58 ± 0.21) kcal th mol −1. The average bond dissociation enthalpies,〈 Do〉(XeF, 298.15 K), are (29.94 ± 0.16), (31.15 ± 0.13), and (31.62 ± 0.16) kcal th mol −1 in XeF 6(g), XeF 4(g), and XeF 2(g), respectively. The enthalpy of formation of PF 3(g) was determined to be −(228.8 ± 0.3) kcal th mol −1. 相似文献
9.
The heat capacity of the solid solution Mn 3.2Ga 0.8N was measured between 5 to 330 K by adiabatic calorimetry. A sharp anomaly with first-order character was detected at TA = (160.5±0.5) K, corresponding to a magnetic rearrangement and a lattice expansion. No sharp anomaly was observed at Tc ≈ 260 K where the magnetic ordering takes place; instead, a smooth shoulder was detected. The thermodynamic functions at 298.15 K are , , , . At low temperatures the coefficient for the linear electronic contribution to the heat capacity was derived: γ = (0.031±0.003) J·K ?2·mol ?1. Moreover, the different contributions to the heat capacity were obtained and the electronic origin of the phase transitions was established. 相似文献
10.
The enthalpies of formation in the crystalline state at 298.15 K of o-, m-, and p-t-butyl-benzoic acids have been determined by static-bomb calorimetry. Vapour-pressure determinations were made by the Knudsen-effusion technique and the sublimation enthalpies at the mean temperatures of the measurement ranges have been derived for the three acids. The values obtained are: | | | | o-t-butylbenzoic acid | 476.2 ± 1.9 | 99.8 ± 0.4 | (at 314.6 K) | m-t-butylbenzoic acid | 504.3 ± 1.6 | 103.0 ± 0.5 | (at 326.5 K) | p-t-butylbenzoic acid | 502.9 ± 1.7 | 103.8 ± 0.4 | (at 334.1 K) | 相似文献
11.
The energies of combustion of 3,4- and 3,5-dimethylbenzoic acids have been revised by combustion calorimetry. Vapour pressures of very pure samples of the six dimethylbenzoic acids have been determined over a range of temperatures near 298 K by the Knudsen-effusion technique. From the experimental results and our previously published thermochemical quantities the following results for the six C 6H 3(CH 3) 2CO 2H isomers at 298.15 K have been derived. Isomer | | | | | kJ·mol?1 | kJ·mol?1 | kJ·mol?1 | 2,6- | ?440.7 ± 1.7 | 99.1 ± 0.2 | ?341.6 ± 1.7 | 2,3- | ?450.4 ± 1.7 | 104.6 ± 0.4 | ?345.8 ± 1.7 | 2,5- | ?456.1 ± 1.6 | 105.0 ± 0.6 | ?351.1 ± 1.7 | 2,4- | ?458.5 ± 1.7 | 103.5 ± 0.3 | ?355.0 ± 1.7 | 3,4- | ?468.8 ± 1.9 | 106.4 ± 0.3 | ?362.4 ± 1.9 | 3,5- | ?466.8 ± 1.7 | 102.3 ± 0.3 | ?364.5 ± 1.7 | 相似文献
13.
Enthalpies of combustion and vaporization at 298.15 K have been measured for 3,5-dithiaheptane and 3,6-dithiaoctane. Enthalpies of formation at 298.15 K have been derived for the compounds in the liquid and gaseous states. The results are: | | | 3,5-Dithiaheptane | ?116.0 ± 1.5 | ?65.2 ± 1.5 | 3,6-Dithiaoctane | ?142.5 ± 1.5 | ?83.0 ± 1.5 | 相似文献
14.
The standard molar Gibbs free energy of formation of NiO was determined in the temperature range 760 to 1275 K from measurements on reversible galvanic cells of the form: . The results can be represented by the equation: ΔfGmo( NiO) = {?232450+83.435( T/ K)} J· mol?1, in excellent agreement with those previously reported. 相似文献
15.
We present the heat capacities measured by adiabatic calorimetry from 6 to 350 K, and by differential scanning calorimetry from 300 to 500 K, of CsCrCl 3 and RbCrCl 3. A first-order transition at Tc = (171.1±0.1) K was detected for CsCrCl 3. The RbCrCl 3 showed at Tc = (193.3±0.1) K a transition with thermal hysteresis at temperatures just below the maximum. At T1 = (440±10) K a continuous transition was also detected. Furthermore, at TN ≈ 16 K, and for both compounds, a small bump due to magnetic long-range ordering was observed. The thermodynamic functions at 298.15 K are | | | | | CsCrCl3 | 15.38 | 26.49 | 3503.2 | 14.735 | RbCrCl3 | 15.76 | 25.99 | 3556.8 | 14.384 | 相似文献
17.
The standard ( po = 101.325 kPa) molar enthalpies of combustion in oxygen at 298.15 K were measured by static-bomb calorimetry and the standard molar enthalpies of sublimation at 298.15 K were measured by microcalorimetry for 1,2-dihydroxybenzene (catechol) and six alkylsubstituted catechols: | | | Catechol | 2864.5 ± 0.8 | 86.6 ± 1.6 | 3-Methylcatechol | 3505.4 ± 0.5 | 93.2 ± 1.0 | 4-Methylcatechol | 3504.6 ± 0.6 | 94.9 ± 1.0 | 3-isoPropylcatechol | 4808.8 ± 1.1 | 97.8 ± 1.7 | 4-terButylcatechol | 5461.9 ± 0.9 | 99.3 ± 1.4 | 3-Methyl-6-isopropylcatechol | 5460.2 ± 0.9 | 96.6 ± 0.9 | 3,5-diterButylcatechol | 8082.7 ± 1.8 | 100.1 ± 0.6 | 相似文献
18.
The low-temperature (5 to 310 K) heat capacity of cesium fluoroxysulfate, CsSO 4F, has been measured by adiabatic calorimetry. At T = 298.15 K, the heat capacity Cpo( T) and standard entropy So( T) are (163.46±0.82) and (201.89±1.01) J · K ?1 · mol ?1, respectively. Based on an earlier measurement of the standard enthalpy of formation ΔHfo the Gibbs energy of formation ΔGfo(CsSO 4F, c, 298.15 K) is calculated to be ?(877.6±1.6) kJ · mol ?1. For the half-reaction: SO 4F ?(aq)+2H +(aq)+2e ? = HSO 4?(aq)+HF(aq), the standard electrode potential E at 298.15 K, is (2.47±0.01) V. 相似文献
19.
The molecular structure and conformation of cis-1,3-dichloro-1-propene have been determined by gas phase electron diffraction at a nozzle temperature of 90°C. The molecule exists in a form in which the chlorine atom of the methyl group and the carbon-carbon double bond are gauche to one another. The results for the distance ( rg) and angle (∠ α) parameters are: r(C-H) = 1.078(10)Å, r(CC) = 1.340(5)Å, r(C-C) = 1.508(7)Å, r( =C-Cl) = 1.762(3)Å, r(C-Cl) = 1.806(3)Å, ∠Cl-C-C = 111.7°(1.8), ∠(CC-C) = 125.5°(1.5), ∠Cl-CC = 124.6°(1.6) and ∠H-C-Cl = 111°(5). The torsion-sensitive distances close to the gauche form can be approximated using a dynamic model with a quartic double minimum potential function of the form V(Φ) = V0[1 + ( 4 - 2( ) 2], where Vo = 1.1(8) kcal mol ?1 and Φ 0 = 56°(5) (Φ = 0 corresponds to the anti form). 相似文献
20.
In order to elucidate the defect structure of the perovskite-type oxide solid solution La 1?xSr xFeO 3?δ ( x = 0.0, 0.1, 0.25, 0.4, and 0.6), the nonstoichiometry, δ, was measured as a function of oxygen partial pressure, PO2, at temperatures up to 1200°C by means of the thermogravimetric method. Below 200°C and in an atmosphere of PO2 ≥ 0.13 atm, δ in La 1?xSr xFeO 3?δ was found to be close to 0. With decreasing log PO2, δ increased and asymptotically reached . The value corresponding to was about ?10 at 1000°C. With further decrease in log PO2, δ slightly increased. For LaFeO 3?δ, the observed δ values were as small as <0.015. It was found that the relation between δ and log PO2 is interpreted on the basis of the defect equilibrium among Sr′ La (or V? La for the case of LaFeO 3?δ), V ··O, Fe′ Fe, and Fe ·Fe. Calculations were made for the equilibrium constants Kox of the reaction and Ki for the reaction Using these constants, the defect concentrations were calculated as functions of PO2, temperature, and composition x. The present results are discussed with respect to previously reported results of conductivity measurements. 相似文献
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