Problem: Use enthalpies of formation given in Appendix C to calculate ΔH for the reaction Br2(g)  →  2 Br(g), and use this value to estimate the bond enthalpy D(Br-Br).Average Bond Enthalpies (kJ/mol)C-H 413N-H 391O-H 463F-F 155C-C 348N-N 163O-O 146C=C 614N-O 201O=O 495Cl-F 253C-N 293N-F 272O-F 190Cl-Cl 242C-O 358N-Cl 200O-Cl 203Br-F 237C=O 799N-Br 243O-I 234Br-Cl 218C-F 485H-H 436Br-Br 193C-Cl 328H-F 567C-Br 276H-Cl 431I-Cl 208C-I 240H-Br 366I-Br 175H-I 299I-I 151

FREE Expert Solution

We are asked to calculate ΔH for the reaction Br₂(g)  →  2 Br(g). 

ΔH°f Br₂(g) = 30.91 kJ/mol

ΔH°f Br(g) = 111.88 kJ/mol

$\boxed{\mathbf{\Delta H}{\mathbf{°}}_{\mathbf{rxn}}\mathbf{=}\mathbf{\Delta H}{\mathbf{°}}_{\mathbf{f}\mathbf{,}\mathbf{ }\mathbf{product}}\mathbf{-}\mathbf{\Delta H}{\mathbf{°}}_{\mathbf{f}\mathbf{,}\mathbf{reactant}}}$

Note that we need to multiply each ΔH˚ by the stoichiometric coefficient since ΔH˚ is in kJ/mol. 

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