Estimate the average $S - F$ bond energy in $S F_{6}$ . The standard heat of formation values of $S F_{6} (g), S (g)$ and $F (g)$ are $- 1100, 275$ and $80 k J m o l^{- 1}$ respectively.

Open in App

Solution

We are given
(i) $\frac{1}{8} S_{8} (s) + 3 F_{8} (g) \to S F_{6} (g) Δ H = - 1100 k J$
(ii) $\frac{1}{8} S_{8} (s) \to S (g) Δ H = 275 k J$
(iii) $\frac{1}{2} F_{2} (g) \to F (g) Δ = 80 k J$
We aim at $\frac{1}{6} [S F_{6} (g) \to S (g) + 6 F (g)]$
Eqn. (ii) $+ 6$ (iii)-(i) gives
$S F_{6} (g) \to S (g) + 6 F (g)$
$Δ H = 275 + 6 \times 80 - (- 1100) = 1855 k J$
$∴$ Average $S - F$ bond energy
$= \frac{1855}{6}$
$= 309.16 k J m o l^{- 1}$

Suggest Corrections

Similar questions

The standard heat of formation values of $S F_{6} (g)$ , $S (g)$ and $F (g)$ are: $- 1100, 275$ and $80 K J m o l^{- 1}$ respectively. Then the average S - F bond energy in $S F_{6}$ is:

The standard heat of formation values of $S F_{6} (g), S (g)$ and $F (g)$ are $- 1100, 275$ and $80$ J mol $^{- 1}$ respecitvely. The $S - F$ bond energy in $S F_{6}$ is :