The average S-F bond energy in $\mathrm{kJ} \mathrm{mol}^{-1}$ of $\mathrm{SF}_{6}$ is_________. (Rounded off to the nearest integer)
[Given : The values of standard enthalpy of formation of $S F_{6}(g), S(g)$ and $F(g)$ are $-1100$, 275 and $80 \mathrm{~kJ} \mathrm{~mol}^{-1}$ respectively.]
$\mathrm{SF}_{6}(\mathrm{~g}) \rightarrow \mathrm{S}(\mathrm{g})+6 \mathrm{~F}(\mathrm{~g})$
If $\in$ - bond enthalpy
$\Delta_{\mathrm{r}} \mathrm{H}=6 \times \epsilon_{\mathrm{S}-\mathrm{F}}$
$=\Delta_{\mathrm{f}} \mathrm{H}(\mathrm{S}, \mathrm{g})+6 \times \Delta_{\mathrm{f}} \mathrm{H}(\mathrm{F}, \mathrm{g})-\Delta_{\mathrm{f}} \mathrm{H}\left(\mathrm{SF}_{6}, \mathrm{~g}\right)$
$=275+6 \times 80-(-1100)$
$=1855 \mathrm{~kJ}$
$\epsilon_{\mathrm{S}-\mathrm{F}}=\frac{1855}{6}=309.16 \mathrm{~kJ} / \mathrm{mol}$
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