DISSOCIATION-ENERGIES OF BAL AND CAL FROM EQUILIBRIUM STUDIES

Effusion-beam mass spectrometry was used to study the gaseous dissociation equilibrium BaI = Ba + I and the isomolecular exchange reactions of BaI and CaI with ScI over wide temperature ranges, and thermochemical data were derived from second law analysis. The results yielded the dissociation energies D0-degrees (BaI) = 76.2 +/- 1.5 kcal mol-1 and D0-degrees (CaI) = 67.0 +/- 2 kcal mol-1. Both of these values are about 5 kcal mol-1 larger than previous results obtained in this laboratory from third law analysis of other reactions. Reasons for the disparities are discussed. Our new second result for BaI is in good agreement with a recent value obtained from crossed molecular beam studies.