Multiple Choice
Use bond energies to estimate the enthalpy change for the formation of HBr(g) from H2(g) and Br2(g). Given: BE(H-H) = 436 kJ/mol, BE(Br-Br) = 192 kJ/mol, BE(H-Br) = 366 kJ/mol.
11. Bonding & Molecular Structure
Bond Energy
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Using the bond energies provided, estimate the standard enthalpy change (ΔH°rxn) for the reaction: XeF2 + 2 F2 → XeF6.
A
-147 kJ/mol
B
-159 kJ/mol
C
-441 kJ/mol
D
-294 kJ/mol
Verified step by step guidance1
Identify the bonds broken and formed in the reaction. In the given reaction, XeF2 and F2 are reactants, and XeF6 is the product. Therefore, bonds in XeF2 and F2 will be broken, and bonds in XeF6 will be formed.
Calculate the total energy required to break the bonds in the reactants. Use the bond energies provided for Xe-F and F-F bonds. Multiply the bond energy of Xe-F by the number of Xe-F bonds in XeF2, and the bond energy of F-F by the number of F-F bonds in 2 F2.
Calculate the total energy released when the bonds in the product XeF6 are formed. Use the bond energy for Xe-F and multiply it by the number of Xe-F bonds in XeF6.
Apply Hess's Law to estimate the standard enthalpy change (ΔH°rxn) for the reaction. Use the formula: ΔH°rxn = (Total energy required to break bonds) - (Total energy released in forming bonds).
Subtract the total energy released from the total energy required to find the estimated ΔH°rxn for the reaction. Ensure the units are consistent throughout the calculation.
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