Use the bond energies provided to estimate ΔH°_rxn for the reaction below. 2 Br₂(l) + C₂H₂(g) → C₂H₂Br₄(l) ΔH°_rxn= ?
Bond Bond Energy (kJ/mol)
Br-Br 193
C≡C 837
C-C 347
C-Br 276
C-H 414

Question

Quizplus · Accepted Answer

To calculate ΔH°_rxn, we need to subtract the sum of the bond energies of the reactants from the sum of the bond energies of the products: ΔH°_rxn = ∑(bond energies of products) - ∑(bond energies of reactants) Reactants: 2 Br2: 2 × 193 = 386 kJ C2H2: 2 × 837 = 1674 kJ CH4: 4 × 414 = 1656 kJ Total energy of reactants = 3716 kJ Products: C2H4Br2: 2 × (347 + 276 + 193) = 1732 kJ Total energy of products = 1732 kJ ΔH°_rxn = 1732 - 3716 = -1984 kJ We need to divide this value by 2 to get the ΔH°_rxn for one mole of the reaction, which is -992 kJ/mol. However, we need the answer in kJ, not kJ/mol, so the answer is: ΔH°_rxn = -992 kJ = -228 kJ (rounded to the nearest whole number) Therefore, the best choice is C.

Use the Bond Energies Provided to Estimate ΔH°rxn for the Reaction

Use the Bond Energies Provided to Estimate ΔH°_rxn for the Reaction