If bond formation energy of $\mathrm{H}-\mathrm{H}$ bond is $-433 \mathrm{~kJ} \mathrm{~mol}^{-1}$ find the…
If bond formation energy of $\mathrm{H}-\mathrm{H}$ bond is $-433 \mathrm{~kJ} \mathrm{~mol}^{-1}$ find the bond dissociation energy for 0.5 mole $\mathrm{H}_{2(\mathrm{~g})}$.
108.0 kJ
216.5 kJ
433.0 kJ
324.5 kJ
Solution
For the given reaction,
$\mathrm{H}_{2(\mathrm{~g})} \longrightarrow 2 \mathrm{H}_{(\mathrm{g})}, \Delta_{\mathrm{r}} \mathrm{H}^{\circ}=433 \mathrm{~kJ} \mathrm{~mol}^{-1}$
(Bond dissociation energy for 1 mole of $\mathrm{H}_{2(\mathrm{~g})}$ $=-\mathrm{H}-\mathrm{H}$ bond formation energy)
$\therefore \quad$ Bond dissociation energy for 0.5 moles of $\mathrm{H}_2=0.5 \times 433 \mathrm{~kJ}=216.5 \mathrm{~kJ}$