Apparent molar heat capacities of aqueous solutions of LiBO2, NaBO2, KBO2, Na2B4O7 and K2B4O7 at T = (298.12, 313.13 and 328.14) K using a Picker flow calorimeter

• Published in: The Journal of chemical thermodynamics 2022-12, Vol.175, p.106879, Article 106879
• Main Authors: Gui, Lingyan, Li, Dongdong, Wu, Jiangtao, Meng, Xianyang
• Format: Article
• Language: English
• Subjects: Apparent molar heat capacity; Lithium metaborate; Potassium metaborate; Potassium tetraborate; Sodium metaborate; Sodium tetraborate
• ISSN: 0021-9614; 1096-3626
• DOI: 10.1016/j.jct.2022.106879

•Apparent molar heat capacities of five borate aqueous solutions were measured.•Standard-state values were obtained using the Pitzer ion-interaction model.•Group contribution method was used to predict the standard state heat capacities.•Three assumptions for possible reactions were discussed. The apparent molar heat capacities of LiBO2(aq), NaBO2(aq), KBO2(aq), Na2B4O7(aq) and K2B4O7(aq) solutions at molalities from 0.01 to 2.6 mol·kg−1, and at temperatures T = (298.12, 313.13 and 328.14) K have been determined using a Picker flow calorimeter built in this work. Further, the standard heat capacities of these solutes were derived from the experimental data by extrapolation to infinite dilution using the Pitzer ion-interaction model. The group contribution method is used to calculate the standard molar heat capacities of tetraborate ion in three equilibria for different assumptions, among which the prediction on the assumption that the standard molar heat capacity of reaction for the association reaction is zero is the most reasonable, and the results are in good agreement with the experimental data.