Consider the following data :
Heat of formation of $\mathrm{CO}_2(\mathrm{~g})=-393.5 \mathrm{~kJ} \mathrm{~mol}^{-1}$
Heat of formation of $\mathrm{H}_2 \mathrm{O}(\mathrm{l})=-286.0 \mathrm{~kJ} \mathrm{~mol}^{-1}$
Heat of combustion of benzene $=-3267.0 \mathrm{~kJ} \mathrm{~mol}^{-1}$
The heat of formation of benzene is _ $\mathrm{kJ} \mathrm{mol}{ }^{-1}$. (Nearest integer)

Question

Aicharya · Accepted Answer

$\begin{aligned} & \Delta \mathrm{H}_{\mathrm{f}}\left[\mathrm{CO}_2(\mathrm{~g})ight]=-393.5 \mathrm{~kJ} / \mathrm{mole} \ & \Delta \mathrm{H}_{\mathrm{f}}\left[\mathrm{H}_2 \mathrm{O}(\ell)ight]=-286.0 \mathrm{~kJ} / \mathrm{mole} \ & \Delta \mathrm{H}_{\mathrm{c}}\left[\mathrm{C}_6 \mathrm{H}_6ight]=-3267.0 \mathrm{~kJ} / \mathrm{mole} \ & \Delta \mathrm{H}_{\mathrm{f}} \mathrm{C}_6 \mathrm{H}_6=(?) \ & \mathrm{C}_6 \mathrm{H}_6+\frac{15}{2} \mathrm{O}_2(\mathrm{~g}) \longrightarrow 6 \mathrm{CO}_2(\mathrm{~g})+3 \mathrm{H}_2 \mathrm{O}(\ell) \ & \Delta \mathrm{H}_{\mathrm{R}}=\Delta \mathrm{H}_{\mathrm{C}}=\Sigma \Delta \mathrm{H}_{\mathrm{f}}(\mathrm{P})-\Sigma \Delta \mathrm{H}_{\mathrm{f}}(\mathrm{R}) \ & -3267=6 	imes(-393.5)+3(-286)-\Delta \mathrm{H}_{\mathrm{f}}\left(\mathrm{C}_6 \mathrm{H}_6ight) \ & \Delta \mathrm{H}_{\mathrm{f}}\left(\mathrm{C}_6 \mathrm{H}_6ight)=48 \mathrm{~kJ} / \mathrm{mole}\end{aligned}$

Consider the following data : Heat of formation of $\mathrm{CO}_2(\mathrm{~g})=-393.5 \mathrm{~kJ}…

Solution