The observed dissociation energy of solid LiBr is 788 kJ/mol. Compute the cohesive energy of LiBr and compare the result with the value in Table 10-1. (Ionization energies for Li and Br are in Table 9-1.)

Table 10-1

Table 9-1

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Solid NaCl LiBr KCI RbF ionic 0.282 ionic 0.275 ionic 0.315 ionic 0.282 ionic 0.348 ionic 0.222 metallic 0.302 metallic 0.248 metallic 0.288 metallic 0.266 covalent 0.154 covalent 0.235 Ge covalent 0.245 H₂O dipole-dipole 0.367 C60 dipole-dipole 1.00 Ne dipole-dipole 0.313 CsCl ZnO Table 10-1 Properties of selected crystalline solids Equilibrium separation (nm) Li Fe Au Zn C Si Bonding Crystal Madelung symmetry constant fcc fcc fcc fcc SC hcp bcc bcc fcc hcp fcc fcc fcc hcp fcc fcc 1.7476 1.7476 1.7476 1.7476 1.7627 1.4985 T 1 T Cohesive Melting energy (eV/atom) point (K) 3.19 3.10 3.24 3.55 3.27 7.22 1.63 4.28 3.81 1.35 7.37 4.63 3.85 0.52* 1.5* 0.020 1074 823 1043 1068 918 2248 454 1811 1338 693 † 1687 1211 273 ? 24