Dissociation energies of CaBr, SrBr, BaBr, and BaCl from mass spectrometric studies of gaseous equilibria

摘要

High temperature gaseous equilibria involving CaBr, SrBr, BaBr, and BaCl were studied by mass spectrometry, and the derived heats of reaction were used to evaluate the dissociation energies of the monohalides. The derived values measured by reference toDdeg;0(AlBr) andDdeg;0(AlCl), areDdeg;0(CaBr) =73.4plusmn;2.2 kcal/mol;Ddeg;0(SrBr) =78.7plusmn;2.2 kcal/mol;Ddeg;0(BaBr) =85.5plusmn;2.2 kcal/mol; andDdeg;0(BaCl) =103.3plusmn;2.0 kcal/mol. These values are in good agreement with results of recent flame equilibrium determination, and with semitheoretical values calculated from both the Rittner polarizablehyphen;ion model and ionicityhyphen;corrected Birgendash;Sponer extrapolations. On the contrary, values ofDdeg;0derived from chemiluminescent metal oxidation reactions are rather higher than those obtained by any of the other methods.