Hydrated potassium monoborate(KBO2 @ 4/3H2O) was obtained from an aqueous solution in a mole ratio ofK2O:B2O3 = 2:1 and characterized by powder X-ray diffraction(XRD), infrared spectroscopy(FT-IR) and Ramanspectroscopy. The enthalpy of solution of hydrated potassium monoborate, KBO2 @ 4/3H2O, in approximatelylmol @ dm-3 aqueous hydrochloric acid was determined. Together with the previously determined enthalpies of so-lution of H3BO3 in approximately 1mol @ dm-3 HCl(aq) , and of KCl in aqueous(hydrochloric acid + boric acid),the standard molar enthalpy of formation of - (1411.11 ± 0. 84)kJ @ mol-1 for KBO2 @ 4/3H2O was obtained fromthe standard molar enthalpies of formation of KCl(s), H3BO3(s), and H2O(1) The standard molar entropy offormation of -422. 94J @ K-1 @ mol-1 and standard molar entropy of 163.47J @ K-1 @ mol-1 for KBO2 @ 4/3H2Owere calculated from the thermodynamic relations. A group contribution method is applicable to KBO2 @ 4/3H2O.
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