JEE MAIN - Chemistry (2021 - 26th February Evening Shift - No. 20)
The average S-F bond energy in kJ mol$$-$$1 of SF6 is _____________. (Rounded off to the nearest integer)
[Given : The values of standard enthalpy of formation of SF6(g), S(g) and F(g) are - 1100, 275 and 80 kJ mol$$-$$1 respectively.]
[Given : The values of standard enthalpy of formation of SF6(g), S(g) and F(g) are - 1100, 275 and 80 kJ mol$$-$$1 respectively.]
Answer
309
Explanation
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So, $\Delta_f H^{\circ}[S, g]+6 \times \Delta_f H^{\circ}[F, g]=\Delta_f H^{\circ}\left[SF_6, g\right]$ $+ 6 \times E_{S-F}$
$\left[\therefore E_{S-F}=\right.$ Average $S-\mathrm{F}$ bond energy in $\left.\mathrm{SF}_6\right]$
$275+6 \times 80=-1100+6 \times E_{S-F}$
$\Rightarrow E_{S-F}=\frac{275+6 \times 80+1100}{6}$ $=309.16 \mathrm{~kJ} \mathrm{~mol}^{-1}=309 \mathrm{~kJ} \mathrm{~mol} \mathrm{~m}^{-1}$
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