Thermodynamics And Thermochemistry Result Question 31
31. The standard heats of formation of $\mathrm{CCl}_4(\mathrm{~g}), \mathrm{H}_2 \mathrm{O}(\mathrm{g})$, $\mathrm{CO}_2(\mathrm{~g})$ and $\mathrm{HCl}(\mathrm{g})$ at $298$ K are $-25.5,-57.8,-94.1$ and $-22.1$ $ \mathrm{kcal} / \mathrm{mol}$ respectively. Calculate $\Delta H^{\circ}(298 \mathrm{~K})$ for the reaction
$\mathrm{CCl}_4(g)+2 \mathrm{H}_2 \mathrm{O}(g) \longrightarrow \mathrm{CO}_2(g)+4 \mathrm{HCl}(g)$
(1982,2 M)
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Answer:
Correct Answer: 31. $(-41.4 $ $\mathrm{kcal})$
Solution: 31.
$\Delta H_r^{\circ} =\Sigma \Delta_f H^{\circ} \text { (products) }-\Sigma \Delta_f H^{\circ} \text { (reactants) } $
$ =-94.1+4(-22.1)-(-25.5-2 \times 57.8) $
$ =-41.4$ $ \mathrm{kcal}$
BETA
