Atomization energies and enthalpies of formation of the SnBi_n (n = 1-3) gaseous molecules by Knudsen cell mass spectrometry

摘要

The equilibria involving the gaseous species SnBi, SnBi_2, and SnBi_3 above the condensed system Bi-Sn contained in a graphite cell have been investigated by the Knudsen effusion technique combined with mass spectrometry. Third law enthalpies for the reactions SnBi_n(g)=Sn(cond) + nBi(g), n = 1-3, were evaluated. By combining the experimental reaction enthalpies with the appropriate thermodynamic data taken from literature, the following atomization energies, #DELTA#_aH_0~0, and enthalpies of formation, #DELTA#_dH_(298.15)~0, in kJ mol~(-1), have been derived: SnBi, 191.1 +- 12.0 and 317.5 +- 12.0; SnBi_2, 415.2 +- 15.0 and 303.0 +- 15.0; SnBi_3, 603,4 +- 18.0 and 323.0 +- 18.0.