Consider the following cases of standard enthalpy of reaction $\left(\Delta \mathrm{H}_{\mathrm{r}}^{\circ}\right.$ in $\left.\mathrm{kJ} \mathrm{mol}^{-1}\right)$ $\begin{aligned} & \mathrm{C}_2 \mathrm{H}_6(\mathrm{~g})+\frac{7}{2} \mathrm{O}_2(\mathrm{~g}) \rightarrow 2…

Question

Consider the following cases of standard enthalpy of reaction $\left(\Delta \mathrm{H}_{\mathrm{r}}^{\circ}\right.$ in $\left.\mathrm{kJ} \mathrm{mol}^{-1}\right)$
$\begin{aligned}
& \mathrm{C}_2 \mathrm{H}_6(\mathrm{~g})+\frac{7}{2} \mathrm{O}_2(\mathrm{~g}) \rightarrow 2 \mathrm{CO}_2(\mathrm{~g})+3 \mathrm{H}_2 \mathrm{O}(\mathrm{l}) ;~\Delta \mathrm{H}_1^{\circ}\\
& =-1550 \\
& \mathrm{C} \text { (graphite) }+\mathrm{O}_2(\mathrm{~g}) \rightarrow \mathrm{CO}_2~(\mathrm{g});~\Delta \mathrm{H}_2^{\circ}=-393.5 \\
& \mathrm{H}_2(\mathrm{~g})+\frac{1}{2} \mathrm{O}_2~(\mathrm{g}) \rightarrow \mathrm{H}_2 \mathrm{O}(\mathrm{l});~\Delta \mathrm{H}_3^{\circ}=-286
\end{aligned}$
The magnitude of $\Delta \mathrm{H}_{f \mathrm{C}_2 \mathrm{H}_6(\mathrm{g})}^{\circ}$ is _______ $\mathrm{kJ} \mathrm{mol}^{-1}$ (Nearest integer).

Aicharya · Accepted Answer

$\begin{aligned} & 2 \mathrm{C}_{	ext {(graphite) }}+3 \mathrm{H}_2(\mathrm{~g}) ightarrow \mathrm{C}_2 \mathrm{H}_6(\mathrm{~g}) \quad \Delta \mathrm{H}_{\mathrm{f}}=? \ & \mathrm{C}_2 \mathrm{H}_6(\mathrm{~g})+\frac{7}{2} \mathrm{O}_2(\mathrm{~g}) ightarrow 2 \mathrm{CO}_2(\mathrm{~g})+3 \mathrm{H}_2 \mathrm{O}(l) \ & \quad \Delta \mathrm{H}_1=-1550 \ & \mathrm{C}_{	ext {(graphite) }}+\mathrm{O}_2(\mathrm{~g}) ightarrow \mathrm{CO}_2(\mathrm{~g}) \Delta \mathrm{H}_2=-393.5 \ & \mathrm{H}_2(\mathrm{~g})+\frac{1}{2} \mathrm{O}_2(\mathrm{~g}) ightarrow \mathrm{H}_2 \mathrm{O}(/) \Delta \mathrm{H}_3=-286 \ & \Delta \mathrm{H}_{\mathrm{f}}=2 \Delta \mathrm{H}_2+3 \Delta \mathrm{H}_3-\Delta \mathrm{H}_1 \ & \quad=95 \mathrm{~kJ} / \mathrm{mole}^2\end{aligned}$

Consider the following cases of standard enthalpy of reaction $\left(\Delta…

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