1. Tardigrade
  2. Question
  3. Chemistry
  4. The average S-F bond energy in kJ mol -1 of SF 6 is .(Rounded off to the nearest integer) [Given: The values of standard enthalpy of formation of SF 6( g ), S ( g ) and F ( g ) are -1100 , 275 and 80 kJ mol -1 respectively.]

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Q. The average $S-F$ bond energy in $kJ \,mol ^{-1}$ of $SF _{6}$ is _____ .(Rounded off to the nearest integer)
[Given : The values of standard enthalpy of formation of $SF _{6}( g ), S ( g )$ and $F ( g )$ are $-1100 , 275$ and $80 \,kJ\, mol ^{-1}$ respectively.]

JEE MainJEE Main 2021Thermodynamics

Solution:

$SF _{6}( g ) \rightarrow S ( g )+6 F ( g )$

If $\in$ - bond enthalpy

$\Delta_{ r } H =6 \times \epsilon_{ S - F }$

$=\Delta_{ f } H ( S , g )+6 \times \Delta_{ f } H ( F , g )-\Delta_{ f } H \left( S F _{6}, g \right)$

$=275+6 \times 80-(-1100)$

$=1855 kJ$

$\epsilon_{ S - F }=\frac{1855}{6}=309.16 kJ / mol$