Journal of Chemical Thermodynamics, Vol.97, 179-182, 2016
Thermochemical properties for a series of transition metal borates of M[B12O14(OH)(10)] (M-II = Mn, Zn, Fe, Co, Ni)
A pure zinc borate, Zn[B12O14(OH)(10)], has been synthesized and characterized by XRD, FT-IR, simultaneous TG-DTA techniques, and chemical analysis. The molar enthalpy of solution of Zn[B12O14(OH)(10)] (s) in 1 mol.dm(-3) HCl(aq) was measured by microcalorimeter at T = 298.15 K. The molar enthalpy of solution of ZnO(s) in the mixture solvent of 2.00 cm(3) of 1 mol.dm(-3) HCl(aq) and calculated amount of H3BO3 was also measured. With the incorporation of the previously determined enthalpy of solution of H3BO3(s) in 1 mol.dm(-3) HCl(aq), together with the use of the standard molar enthalpies of formation for ZnO(s), H3BO3(s), and H2O(l), the standard molar enthalpy of formation of -(9646.6 +/- 9.6) kJ.mol(-1) at T = 298.15 K was obtained on the basis of an appropriate thermochemical cycle. In addition, the molar enthalpy of formation of -9492.7 kJ.mol(-1) for [B12O14(OH)(10)](2) has also been estimated by a group contribution method, which has been used to predict the Lambda H-f(m)theta of a series of transition metal borates of M [B12O14(OH)(10)] (M-II = Mn, Zn, Fe, Co, Ni). These estimated data have been used to further compare the stability of this series of transition metal borates. (C) 2016 Elsevier Ltd. All rights reserved.
Keywords:Transition metal borates;Standard molar enthalpy of formation;Solution calorimetry;A group contribution method