The standard molar atomization enthalpy and the standard molar enthalpy of formation of gaseous Si2N from high-temperature mass spectrometry

✍ Scribed by R. Viswanathan; R.W. Schmude Jr.; K.A. Gingerich

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 380 KB
• Volume: 27
• Category: Article
• ISSN: 0021-9614
• DOI: 10.1006/jcht.1995.0138

✦ Synopsis

A high-temperature mass-spectrometric study of the vaporization of (silicon+boron nitride) from a boron-nitride Knudsen cell was conducted in the temperature range T = 1688 K to 1921 K. The partial pressures of Si(g), Si2(g), N2(g), and Si2N(g) were determined. The dissociation reaction: Si2N(g)=2Si(g)+0.5N2(g) was evaluated by using new thermal functions for Si2N(g) calculated from the results of recent theoretical and experimental studies, and DrH°m values: (538.0212.4) kJ•mol -1 at T :0, and (545.1212.4) kJ•mol -1 at T = 298.15 K were deduced by third-law evaluation. These values, in combination with the molar dissociation enthalpy of N2(g) yielded the molar atomization enthalpies: DatH°m(Si2N,g) = (1008.8 2 12.4) kJ•mol -1 at T : 0, and (1017.8 2 12.4) kJ•mol -1 at T=298.15 K, and in combination with the standard molar enthalpy of formation of Si(g) yielded: DfH°m(Si2N, g)=(354.0214.8) kJ•mol -1 at T : 0, and (355.6214.8) kJ•mol -1 at T=298.15 K.