$2 \mathrm{Fe}_{(\mathrm{s})}+\frac{3}{2} \mathrm{O}_{2(\mathrm{~g})} \rightarrow \mathrm{Fe}_2 \mathrm{O}_{3(\mathrm{~s})}, \Delta \mathrm{H}^{\mathrm{o}}=-822 \mathrm{~kJ} / \mathrm{mol}$
$\mathrm{C}_{(\mathrm{s})}+\frac{1}{2} \mathrm{O}_{2(\mathrm{~g})} \rightarrow \mathrm{CO}_{(\mathrm{g})}, \Delta \mathrm{H}^{\mathrm{o}}=-110 \mathrm{~kJ} / \mathrm{mol}$
$3\mathrm{C}_{(\mathrm{s})}+\mathrm{Fe}_2 \mathrm{O}_{3(\mathrm{~s})} \rightarrow 2 \mathrm{Fe}_{(\mathrm{s})}+3 \mathrm{CO}_{(\mathrm{g})}$ આપેલા પ્ર્ક્રિયા માટે એન્થાલ્પી ફેરફાર__ _ _$J/mol$ છે.
$\mathrm{C}_{(\mathrm{s})}+\frac{1}{2} \mathrm{O}_{2(\mathrm{~g})} \rightarrow \mathrm{CO}_{(\mathrm{g})}, \Delta \mathrm{H}^{\mathrm{o}}=-110 \mathrm{~kJ} / \mathrm{mol}$ $.......(2)$
$3\mathrm{C}_{(\mathrm{s})}+\mathrm{Fe}_2 \mathrm{O}_{3(\mathrm{~s})} \rightarrow 2 \mathrm{Fe}_{(\mathrm{s})}+3 \mathrm{CO}_{(\mathrm{g})}, \Delta \mathrm{H}_3=\text { ? }$
$\text { (3) }=3 \times(2)-(1)$
$\Delta \mathrm{H}_3=3 \times \Delta \mathrm{H}_2-\Delta \mathrm{H}_1$
$=3(-110)+822$
$=492 \mathrm{~kJ} / \mathrm{mole}$+
આપેલ : $\Delta H _{ f }{ }^\theta\left( Al _2 O _3\right)=-1700\,kJ\,mol ^{-1}$
$\Delta H _{ f }{ }^\theta\left( Fe _2 O _3\right)=-840\,kJ\,mol ^{-1}$
$Fe , Al$ અને $O$ નું મોલર દળ અનુક્રમે $56,27$ અને $16\,g\,mol ^{-1}$.
$\left[\right.$ ઉપયોગ $: {H}^{+}({aq})+{OH}^{-}({aq}) \rightarrow {H}_{2} {O}: \Delta_{{\gamma}} {H}=-57.1\, {k} {J} \,{mol}^{-1},$
વિશિષ્ટ ઊર્જા ${H}_{2} {O}=4.18 {Jk}^{-} {g}^{-},$
ઘનતા ${H}_{2} {O}=1.0\, {~g} {~cm}^{-3},$
મિશ્રણ પર દ્રાવણના કદમાં કોઈ ફેરફાર થતો નથી એમ ધારો.]