Atomization energies of gaseous AlPd and Al2Pd
Abstract
Knudsen cell mass spectrometry has been used to investigate the gaseous equilibrium reactions (1) AlPd(g)⇌ Al(g)+ Pd(g) and (2) Al2Pd(g)+ Pd(g)⇌ 2AlPd(g). The reaction enthalpies ΔH00 are (1) 250.6 ± 12.0 kJ mol–1 and (2)–8.8 ± 3.0 kJ mol–1 where the second and third law procedures were used to obtain the value for reaction (1) and the third law procedure for reaction (2). The atomization energies derived from these reaction enthalpies are: D00(AlPd)= 250.6 ± 12.0 kJ mol–1 and D00(Al2Pd)= 492.4 ± 24 kJ mol–1. The corresponding standard heats of formation, ΔH0f,298 are AlPd: 451.8 ± 12.5 kJ mol–1 and Al2Pd: 536.4 ± 24.3 kJ mol–1. The bonding in these molecules is discussed in terms of empirical models.