Thermodynamic properties for two mixed alkali-transition metal borates of Li6Zn3B4O12 and Na3ZnB5O10

Two pure mixed alkali-transition metal borates, Li 6 Zn 3 B 4 O 12 (s) and Na 3 ZnB 5 O 10 (s) have been synthesized and characterized by XRD, FT-IR, and chemical analysis. For Li 6 Zn 3 B 4 O 12 , the molar enthalpy of solution of Li 6 Zn 3 B 4 O 12 in the mixture solvent of {2.00 mL of 1 mol·L −1 HCl + H 3 BO 3 )(aq)} was measured. The molar enthalpies of solution of ZnO(s) in 1 mol·L −1 HCl(aq), and LiBO 2 (s) in the mixture solvent of {2.00 mL of 1 mol·L −1 HCl(aq) + ZnO(aq)} were also measured. For Na 3 ZnB 5 O 10 , the molar enthalpy of solution of Na 3 ZnB 5 O 10 in 2.00 mL of 1 mol·L −1 HCl(aq) was measured. The molar enthalpy of solution of NaBO 2 ·4H 2 O(s) in the mixture solvent of {2.00 mL of 1 mol·L −1 HCl(aq) + H 3 BO 3  + ZnO](aq)} was also measured. With the incorporation of the previously determined enthalpy of solution of H 3 BO 3 (s) in 1 mol·L −1 HCl(aq), and ZnO(s) in {1 mol·L −1 HCl(aq) + H 3 BO 3 }, together with the use of the standard molar enthalpies of formation for LiBO 2 (s)/NaBO 2 ·4H 2 O(s), ZnO(s), H 3 BO 3 (s) and H 2 O(l), the standard molar enthalpies of formation of −(5867.5 ± 4.8) kJ·mol −1 for Li 6 Zn 3 B 4 O 12 and −(4655.3 ± 6.6) kJ·mol −1 for Na 3 ZnB 5 O 10 at T  = 298.15 K were obtained on the basis of two appropriate thermochemical cycles.