Thermodynamics And Thermochemistry Result Question 17
17. Estimate the average $\mathrm{S}-\mathrm{F}$ bond energy in $\mathrm{SF} _6$. The values of standard enthalpy of formation of $\mathrm{SF} _6(g), \mathrm{S}(g)$ and $\mathrm{F}(g)$ are : $-1100,275$ and $80 \mathrm{~kJ} \mathrm{~mol}^{-1}$ respectively.
(1999, 3 M)
Show Answer
Answer:
Correct Answer: 17. $(309.16 \mathrm{~kJ})$
Solution:
- $\mathrm{SF}_6(g) \longrightarrow \mathrm{S}(\mathrm{g})+6 \mathrm{~F}(\mathrm{~g})$
$\Delta H=\Sigma \Delta H_f^{\circ} \text { (products) }-\Sigma \Delta H_f^{\circ} \text { (reactants) }$
$=275+6 \times 80+1100=1855 \mathrm{~kJ}$
$\Rightarrow \text { Average S—F bond energy }=\dfrac{1855}{6}=309.16 \mathrm{~kJ} / \mathrm{mol}$
BETA
