Vapor pressure measurements of CuBr and ZnBr_2 by the Knudsen effusion method and their vapor species identification

摘要

Vapor pressures over CuBr and ZnBr_2 solids were measured by the Knudsen effusion method assuming that the vapor species consisted solely of trimers and monomers, respectively. The vapor pressures fitted the following linear equations over the temperature ranges considered:CuBr, ln(p/Pa) =- (14936 ± 371) (K/T) + (23.73 ± 0.63)(from 528.8 to 658.2K);and ZnBr_2, ln (p/Pa) = - (13867 ± 247)(K/T) + (26.68 ± 0.49) (from 452.5 to 574.0K).The standard sublimation enthalpies for CuBr and ZnBr_2 were estimated to be 124.2 ± 3.1 and 115.3 ± 2.1 kJ/mol, and the standard sublimation entropies were estimated as 197.3 ± 5.2 and 221.8 ± 4.1 J/(mol K), respectively. Identification of the predominant vapor species from each metal bromide was conducted using mass spectrometry. From the analysis, it was confirmed that the main vapor species were the trimer (Cu_3Br_3) for CuBr and the monomer (ZnBr_2) for ZnBr_2.