Thermodynamics And Thermochemistry Result Question 32
32. The enthalpy for the following reactions $\left(\Delta H^{\circ}\right)$ at $25^{\circ} \mathrm{C}$ are given below
(i) $\frac{1}{2} \mathrm{H}_2(g)+\frac{1}{2} \mathrm{O}_2(g) \longrightarrow \mathrm{OH}(g) \quad \Delta H^{\circ}=-10.06 $ $\mathrm{kcal}$
(ii) $\mathrm{H}_2(\mathrm{~g}) \longrightarrow 2 \mathrm{H}(\mathrm{g}) \quad \Delta H^{\circ}=104.18$ $ \mathrm{kcal}$
(iii) $\mathrm{O}_2(g) \longrightarrow 2 \mathrm{O}(\mathrm{g}) \quad \Delta H^{\circ}=118.32 $ $\mathrm{kcal}$
Calculate the $\mathrm{O}-\mathrm{H}$ bond energy in the hydroxyl radical.
(1981, 2M)
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Answer:
Correct Answer: 32. $(121.31$ $ \mathrm{kcal})$
Solution:
$ \Delta H^{\circ}=\Sigma \mathrm{BE} \text { (reactants) }-\Sigma \mathrm{BE} \text { (products) }$
$ \Rightarrow \quad-10.06=\frac{1}{2}(104.18)+\frac{1}{2}(118.32)-\mathrm{BE}(\mathrm{O}-\mathrm{H})$
$ \mathrm{BE}(\mathrm{O}-\mathrm{H})=121.31 \mathrm{kcal}$
BETA
