The reaction is exothermic with

CHEMISTRY · Single correct · A Level · Chemistry · Energetics · Energetics

Problem

The reaction

\mathrm{H_2(g) + I_2(g) \rightarrow 2HI(g)}

is exothermic with

\Delta H_{\text{rxn}} = -26\,\text{kJ\,mol}^{-1}

. The average bond energies for the bonds broken are

D(\mathrm{H\! -\! H}) = 436\,\text{kJ\,mol}^{-1}

and

D(\mathrm{I\! -\! I}) = 151\,\text{kJ\,mol}^{-1}

. Which of the following ranges is most consistent with the average bond energy of the

\mathrm{H\! -\! I}

bond formed in the products? (a)

\approx 613\,\text{kJ mol}^{-1}

(b)

\approx 280\,\text{kJ mol}^{-1}

(c)

\approx 307\,\text{kJ mol}^{-1}

(d)

\approx 294\,\text{kJ mol}^{-1}