QJEEM23Ch04aa: JEE Main 2023 Chemistry - Class 11 JEEM23Ch04aa Solution: At , the enthalpy of the following processes are given : .tg…

Question

Verified Solution • 2025–26 Session moderate

At $25^{\circ} \mathrm{C}$ , the enthalpy of the following processes are given :

$\mathrm{H_2(g)+O_2(g)}$	$\to$	$2\mathrm{OH(g)}$	$\mathrm{\Delta H^\circ=78~kJ~mol^{-1}}$
$\mathrm{H_2(g)+\frac{1}{2}O_2(g)}$	$\to$	$\mathrm{H_2O(g)}$	$\mathrm{\Delta H^\circ=-242~kJ~mol^{-1}}$
$\mathrm{H_2(g)}$	$\to$	$\mathrm{2H(g)}$	$\mathrm{\Delta H^\circ=436~kJ~mol^{-1}}$
$\frac{1}{2}\mathrm{O_2(g)}$	$\to$	$\mathrm{O(g)}$	$\mathrm{\Delta H^\circ=249~kJ~mol^{-1}}$

What would be the value of X for the following reaction ? _____________ (Nearest integer)

$\mathrm{H_2O(g)\to H(g)+OH(g)~\Delta H^\circ=X~kJ~mol^{-1}}$

Accepted Answer

\frac{\text { (i) }+\text { (iii) }}{2}-

(ii) gives desired reaction

\begin{aligned}&amp; \Delta \mathrm{H}_{\mathrm{r}}=\frac{436+78}{2}-(-242) \\\\&amp; =\frac{436+78}{2}+242=499\end{aligned}

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