Saturation Vapor Pressure of Water over Sodium Borohydride Dihydrate

• Published in: Russian journal of applied chemistry 2023-05, Vol.96 (5), p.562-565
• Main Authors: Shikhovtsev, A. V., Kravchenko, O. V., Vinokurov, A. A., Solov’ev, M. V., Tsvetkov, M. V., Dobrovol’skii, Yu. A.
• Format: Article
• Language: English
• Subjects: Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Enthalpy; Entropy; Industrial Chemistry/Chemical Engineering; Physicochemical Studies of Systems and Processes; Relative humidity; Vapor pressure; Water vapor
• ISSN: 1070-4272; 1608-3296
• DOI: 10.1134/S1070427223050075

The relative humidity and saturated water vapor pressure resulted from the reversible equilibrium dissociation of crystalline NaBH 4 ·2H 2 O in the temperature range 0–36°C were determined. Based on the data obtained for NaBH 4 ·2H 2 O, the equilibrium water vapor pressure as a function of temperature ln P = –6567.1 T –1 + 23.863, enthalpy ∆ Н 0 = 54 ± 0.8 kJ mol –1 and entropy ∆ S 0 =198 ± 2 J mol –1 K –1 of NaBH 4 ·2H 2 O dissociation into NaBH 4 and H 2 O, standard enthalpy ∆ H °= –783 kJ mol –1 and entropy ∆ S ° = 281 J mol –1 K –1 of formation of NaBH 4 ·2H 2 O were calculated. An equation was derived for the humidity vs. temperature, which determines the regions of NaBH 4 ·2H 2 O formation or its dissociation Rh = 0.334 t + 17.5. It was shown that the pressure of saturated water vapor over a concentrated NaBH 4 solution (30 wt %) at temperatures up to 45°C has higher values compared to NaBH 4 ·2H 2 O samples synthesized by two different methods.