The bond dissociation energies of , , and are observed to be in the ratio 1:0.5:1. If the standard e — Thermodynamics and Thermochemistry Chemistry Question

💡 Solution & Explanation

Let the bond energies be $x$, $0.5x$, and $x$. The formation reaction is $0.5 X_2 + 0.5 Y_2 \rightarrow XY$. $\Delta H_f = \sum BE_{reactants} - \sum BE_{products} = [0.5(x) + 0.5(0.5x)] - x = 0.75x - x = -0.25x$. Setting $-0.25x = -200$ yields $x = 800$ kJ/mol.