Answer:
-1104 kJ
Explanation:
C + O=O ⟶ O=C=O
Bonds: O=O 2C=O
<em>D</em>/kJ·mol⁻¹: 494 799
The formula relating Δ<em>H</em>rxn and bond dissociation energies (<em>D</em>) is
Δ<em>H</em>rxn = Σ(<em>D</em>reactants) – Σ(<em>D</em>products)
(Note: This is an <em>exception</em> to the rule. All other thermochemical reactions are “products – reactants”. With bond energies, it’s “reactants – products”. The reason comes from the way we define bond energies.)
<em>For the reactants</em>:
Σ(<em>D</em>reactants) = 1 × 494 = 494 kJ
<em>For the products</em>:
Σ(<em>D</em>products) = 2 × 799 = 1598 kJ
<em>For the reaction
:</em>
Δ<em>H</em>rxn = 494 – 1598 = -1104 kJ