Hydrothermal Synthesis and Standard Molar Enthalpy of Formation of Zinc Borate of 4ZnO•B2O3•H2O

The zinc borate 4ZnO center dot B2O3 center dot H2O has been synthesized and characterized by means of chemical analysis, X-ray diffraction (XRD), FT-IR, and DTA-TG. The measured molar enthalpy Of Solution Of 4ZnO center dot B2O3 center dot H2O(S) in HCl center dot 54.572H(2)O is -(265.64 +/- 0.11) kJ.mol(-1). With previously determined enthalpies of solution of H3BO3(s) in 1 mol.dm(-3)HCl(aq) and of ZnO(s) in (HCl + H3BO3) aqueous solution, 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 for 4ZnO center dot B2O3 center dot H2O(s) was calculated as -(3030.46 +/- 1.72) kJ.mol(-1).