Thermodynamics Research Center, ThermoML : Journal of Chemical Thermodynamics

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

Liang, P.[Pan], Li, S.-Y.[Sa-Ying]
J. Chem. Thermodyn. 2019, 139, 105868
ABSTRACT
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.
Compounds
# Formula Name
1 B boron
2 Zn zinc
3 O2 oxygen
4 H2 hydrogen
5 B4O7Zn zinc tetraborate (ZnB4O7)
6 B4H6O11Zn2 zinc(II) metaborate trihydrate (2ZnO*2B2O3*3H2O)
Datasets
The table above is generated from the ThermoML associated json file (link above). POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied; the numbers refer to the table of compounds on the left.
Type Compound-# Property Variable Constraint Phase Method #Points
  • RXND
  • 1
  • 2
  • 5
  • 3
  • Molar enthalpy of reaction, kJ/mol
  • Solution calorimetry
  • 1
  • RXND
  • 1
  • 2
  • 6
  • 4
  • 3
  • Molar enthalpy of reaction, kJ/mol
  • Solution calorimetry
  • 1