Given the average bond energies listed below, estimate D H for the following reaction:
3 H₂ + N₂→2 NH₃ D H _rxn = ??
Average Bond Energies:
H - H₄36 kJ/mol N º N 946 kJ/mol N - N 163 kJ/mol N - H 389 kJ/mol

Question

Quizplus · Accepted Answer

The correct answer is A because the change in enthalpy for the reaction is equal to the sum of the bond energies of the reactants minus the sum of the bond energies of the products. In this case, the bond energies of the reactants are 3(436 kJ/mol) + 946 kJ/mol = 2254 kJ/mol, and the bond energies of the products are 6(389 kJ/mol) = 2334 kJ/mol. Therefore, the change in enthalpy for the reaction is 2254 kJ/mol - 2334 kJ/mol = -80 kJ/mol.

Given the Average Bond Energies Listed Below, Estimate D H