Thermochemistry of the gaseous uranium bromides UBr through UBr/sub 5/

Journal Article · Sun Mar 01 04:00:00 EST 1987 · J. Chem. Phys.; (United States)

OSTI ID:6868740

Lau, K H; Hildenbrand, D L

High temperature gaseous equilibria involving the molecular species UBr, UBr/sub 2/, UBr/sub 3/, UBr/sub 4/, and UBr/sub 5/ were studied by mass spectrometry over wide temperature ranges; reaction enthalpy data were derived primarily from second-law analysis. From this information, the individual bond dissociation energies and the standard enthalpies of formation of the U--Br species were derived with an accuracy of about 8 kJ mol/sup -1/. The derived bond dissociation energies at 298 K in kJ mol/sup -1/ are as follows: D /sup 0/(U--Br) = 377; D /sup 0/(BrU--Br) = 435; D /sup 0/(Br/sub 2/U--Br) = 430; D /sup 0/(Br/sub 3/U--Br) = 348; and D /sup 0/(Br/sub 4/U--Br) = 166. Trends in these values are similar to those found in the U--Cl system, but quite different from those of the U--F system. Absolute entropies evaluated from the equilibrium data indicate significant electronic contributions for the lighter species, decreasing markedly on approaching UBr/sub 5/. Trends in the bond dissociation energies and electronic entropies of the fluorides, chlorides, and bromides are discussed.

• Research Organization: SRI International, Menlo Park, California 94025
• OSTI ID: 6868740
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 86:5; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ACTINIDE COMPOUNDS
BROMIDES
BROMINE COMPOUNDS
CARBIDES
CARBON COMPOUNDS
CHEMICAL BONDS
DISSOCIATION HEAT
ENTHALPY
EQUILIBRIUM
FLUIDS
GASES
HALIDES
HALOGEN COMPOUNDS
HIGH TEMPERATURE
MASS SPECTROSCOPY
PHYSICAL PROPERTIES
REACTION HEAT
SPECTROSCOPY
THERMOCHEMICAL PROCESSES
THERMODYNAMIC PROPERTIES
URANIUM BROMIDES
URANIUM CARBIDES
URANIUM COMPOUNDS