Electron-impact and thermodynamic studies of potassium metaborate
Abstract
An effusion–mass spectrometric investigation of the thermodynamic properties of KBO2(g) has been made in the temperature range 1053–1240 K. The KBO2(g) molecule fragments to over 90% of its initial concentration at electron ionization energies 2 eV above its ionization potential of 8 ± 1 eV. The fragmentation processes were studied to ionization energies as high as 70 eV, with the appearance of K+, BO+2 and BO+ fragments. Data obtained for the sublimation process, KBO2(c)→ KBO2(g), and for the vaporization process, KBO2(1)→ KBO2(g), yielded second- and third-law reaction heats. A third-law ΔH⊖f298 of –672.4 ± 10 kJ mol–1 and a second-law ΔH⊖f298 of –672.8 ± 10 kJ mol–1 were obtained for KBO2(g). A heat of melting, ΔH⊖m, at the melting point of 1220 K was found to be 31.8 ± 4 kJ mol–1.
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