If the bond energies of H-H, Br-Br, and H-Br are 433, 192 and 364 kJ mol−1 respectively, the △H0 for the reaction H2(g)+Br2(g)→2HBr(g) is:
Use bond energies to estimate the enthalpy of formation of HBr(g). BE(H-H) = 436 kJ/mol BE(Br-Br) = 192 kJ/mol BE(H-Br) = 366 kJ/mol