From the values obtained for the standard enthalpies of the reaction ( 5 ) and by using appropriate thermochemical cycles [ 27 ], the following thermochemical parameters for the adducts were determined: the standardenthalpiesofformation (Δ f H θ
Authors:Sonia Jebri, Habib Boughzala, Ali Bechrifa, and Mohamed Jemal
increases ( Fig. 7 ). The uncertainties on these values can not been determined because the literature values are given without any error.
Standardenthalpiesofformation at 298 K calculated according
Authors:Y. Xu-Wu, Z. Hang-Guo, S. Wu-Juan, W. Xiao-Yan, and G. Sheng-Li
The copper(II) complex of 6-benzylaminopurine (6-BAP) has been prepared with dihydrated cupric chloride and 6-benzylaminopurine.
Infrared spectrum and thermal stabilities of the solid complex have been discussed. The constant-volume combustion energy,
ΔcU, has been determined as −12566.92±6.44 kJ mol−1 by a precise rotating-bomb calorimeter at 298.15 K. From the results and other auxiliary quantities, the standard molar enthalpy
of combustion, ΔcHmθ, and the standard molar of formation of the complex, ΔfHmθ, were calculated as −12558.24±6.44 and −842.50±6.47 kJ mol−1, respectively.
The combustion energy of thioproline was determined
by the precision rotating-bomb calorimeter at 298.15 K to be ΔcU= –2469.301.44 kJ mol–1.
From the results and other auxiliary quantities, the standard molar enthalpy
of combustion and the standard molar enthalpy of formation of thioproline
were calculated to be ΔcHmθC4H7NO2S,
(s), 298.15 K= –2469.921.44 kJ mol–1
and ΔfHmθC4H7NO2S, (s), 298.15K= –401.331.54
The standard molar enthalpy of formation ΔfHm0=–760±12 kJ for amorphous silicon nitride a-Si3N4 has been determined from fluorine combustion calorimetry measurements of the massic energy of the reaction: a-Si3N4(s)+6F2(g)=3SiF4(g)+2N2(g). This value combined with ΔfHm0= –828.9±3.4 kJ for a-Si3N4 indicates that determined for the first time molar enthalpy change for the transition from amorphous to α-crystalline form
ΔtrsHm0=69±13 kJ is very evident, in spite of its large uncertainty range resulting from impurity corrections.
Thermochemical and thermodynamical properties of HTSC phases are reviewed for the Y-Ba-Cu-O system and also presented for the newly calculated Bi-Sr-Cu-O system stressing out stoichiometric and phenomenological viewpoints. Simulated data are listed for (H298o-Hoo, phase transformation temperatures, standard entropies, standard enthalpies of formation, heat capacities in crystalline phase, etc. Pseudobinary phase diagrams are treated showing the effect of oxygen partial pressure particularly illustrated on the (Sr, Bi, Ba)-Cu-O system.
Authors:V. Vasil'ev, A. Lytkin, and N. Chernyavskaya
The enthalpies of dissolution of ZrCl4, ZrBr4, HfCl4 and HfBr4 in water in weakly acidic and alkaline solutions were measured at 25C in a calorimeter provided with an isothermal cover.
The standard enthalpies of formation of Zr(OH)4 and Hf(OH)4 in solution were measured. The thermodynamic characteristics of the reactions which resulted in the formation of tetrahydroxy
complexes of Zr and Hf in aqueous solution were also determined.
By using a DSK of the French firm Seteram, the standard enthalpies of formation of 5 tellurites and 5 tetratellurites of the
rare earths Gd, Tb, Dy, Tm and Yb were determined for the first time.
Three parallel determinations for each sample were compared. The results are very similar, which is an indication of the great
reliability of the method used and the correctness of the data obtained.
Authors:M. Ji, J. Liu, S. Gao, B. Kang, R. Hu, and Q. Shi
The enthalpies of solution in water of RE(His)(NO3)3
H2O (RE=La—Nd, Sm—Lu, Y) were measured calorimetrically at 298.15 K, and the standard enthalpies of formation of RE(His)aq3+ (RE=La—Nd, Sm—Lu, Y) were calculated. The plot of the enthalpies of solution vs. the atomic numbers of the elements in the lanthanide series exhibits the tetrad effect.