Thermodynamic properties of K2Sr[B4O5(OH)4]2·10H2O

A pure hydrated double strontium borates, K2Sr[B4O5(OH)4]2·10H2O, has been synthesized and characterized by XRD, FT-IR, DTA–TG and chemical analysis. The enthalpies of solution of K2Sr[B4O5(OH)4]2·10H2O in 1 mol dm−3 HCl(aq) and KCl(s) in mixed solvent [1 mol dm−3 HCl + Sr(OH)2·8H2O + H3BO3](aq) were determined. With the incorporation of the previously determined enthalpies of solution of Sr(OH)2·8H2O(s) in [1 mol dm−3 HCl + H3BO3](aq), H3BO3(s) in 1 mol dm−3 HCl(aq) and the standard molar enthalpies of formation of HCl(aq), H2O(l), Sr(OH)2·8H2O(s), H3BO3(s) and KCl(s), the standard molar enthalpy of formation of K2Sr[B4O5(OH)4]2·10H2O was found to be −(10882.0 ± 6.5) kJ mol−1. Thermodynamic properties of the compound were also estimated by a group contribution method. The standard molar free energy of formation image was estimated to be −9690.80 kJ mol−1. From these values, the standard molar entropy of formation image was estimated to be −3995.3 J mol−1 K−1. The standard molar entropy image was estimated to be 933.8 J mol−1 K−1.