Equilibrium pressure of water vapor over a Li 2O(s)-LiOH(s, 1) mixture

Abstract

Equilibrium water vapor pressures above the Li 2O-H 2O-LiOH system were measured accurately over the temperature range from 570 to 820 K. The values are expressed by the following equations: above the melting point of LiOH, log 10 P/ Pa = (−4074/ T + 8.021) ± 0.006; below the melting point of LiOH, log 10 P/ Pa = (−6462/ T + 11.22) ± 0.008. The enthalpy change and the entropy change in the decomposition reaction of LiOH(s, 1) including the solubility-limit of Li 2O(s) were determined to be 123.7±0.18 kJ mol −1 and 118.4 ± 0.16 J mol −1 K −1 at 601–740 K, and 78.00 ± 0.10 kJ mol −1 and 57.72 ± 0.12 J mol −1 K −1 at 749–820 K, respectively. The enthalpy change and the entropy change of melting of LiOH were also obtained: 22.85 ± 0.14 kJ mol −1 and 30.34 ± 0.28 J mol −1 K −1, respectively.