Consider the following cases of standard enthalpy of reaction (Δ H_r^°. in. kJ mol^-1) C_2 H_6( g )+7/2 O_2( g ) → 2 CO_2( g )+3 H_2 O ( l ) Δ…

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