Heat Capacities and Thermodynamic Properties of a H2O + Li2B4O7 Solution in the Temperature Range from 80 to 356 K |
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Authors: | Zhi-Heng Zhang Guo-Yin Yin Zhi-Cheng Tan Yan Yao Li-Xian Sun |
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Affiliation: | (1) Thermochemistry Laboratory, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, P.R. China;(2) Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining, 810008, P.R. China;(3) Graduate School of the Chinese Academy of Sciences, Xi’an, P.R. China |
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Abstract: | The molar heat capacities of an aqueous Li2B4O7 solution were measured with a precision automated adiabatic calorimeter in the temperature range from 80 to 356 K at a concentration of 0.3492 mol⋅kg−1. The occurrence of a phase transition was determined based on the changes in the curve of the heat capacity with temperature. A phase transition was observed at 271.72 K corresponding to the solid-liquid phase transition; the enthalpy and entropy of the phase transition were evaluated to be Δ H m = 4.110 kJ⋅mol−1 and Δ S m = 15.13 J⋅K−1⋅mol−1, respectively. Using polynomial equations and thermodynamic relationship, the thermodynamic functions [H T −H 298.15] and [S T −S 298.15] of the aqueous Li2B4O7 solution relative to 298.15 K were calculated in temperature range 80 to 355 K at intervals of 5 K. Values of the relative apparent molar heat capacities of the aqueous Li2B4O7 solution, C p,φ, were calculated at every 5 K in temperature range from 80 to 355 K from the experimental heat capacities of the solution and the heat capacities of pure water. |
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Keywords: | Heat capacity Aqueous Li2B4O7 Adiabatic calorimetry Relative apparent molar heat capacity Thermodynamic function |
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