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

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Abstract
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 to D°0(AlBr) and D°0(AlCl), are D°0(CaBr) =73.4±2.2 kcal/mol; D°0(SrBr) =78.7±2.2 kcal/mol; D°0(BaBr) =85.5±2.2 kcal/mol; and D°0(BaCl) =103.3±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 polarizable‐ion model and ionicity‐corrected Birge–Sponer extrapolations. On the contrary, values of D°0 derived from chemiluminescent metal oxidationreactions are rather higher than those obtained by any of the other methods.