\(\left[ {\begin{array}{*{20}{c}}
\begin{gathered}
4(C - H\,) \hfill \\
\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, + \hfill \\
\end{gathered} \\
\begin{gathered}
C = C \hfill \\
\,\,\,\,\,\,\,\,\, \,\, + \, \hfill \\
\end{gathered} \\
\begin{gathered}
{\text{H - H}}\, \hfill \\
\,\,\,\,\,\,\,\,\,\,\,\,\, + \hfill \\
\end{gathered}
\end{array}} \right]\,\, - \,\,\left[ {\begin{array}{*{20}{c}}
\begin{gathered}
6(C - H\,) \hfill \\
\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, + \hfill \\
\end{gathered} \\
{{\text{C - C}}\,}
\end{array}} \right]\)
\(= [4(414) + 615 + 435] - [ 6(414) + 347] = -125\) જૂલ
$NH _{2} CN _{( s )}+\frac{3}{2} O _{2}( g ) \rightarrow N _{2( g )}+ O _{2}( g )+ H _{2} O _{(l)}$
$\Delta H _{298}$ ની માત્રા ........ $kJ$ છે. (નજીક પૂર્ણાંક રાઉન્ડ ઓફ)
[ધારી લો આદર્શ વાયુઓ અને $\left. R =8.314\, J\, mol ^{-1} K ^{-1}\right]$
$(i)$ $N_2H_4$$_{(l)}$ $+$ $2H_2O_2$$_{(l)}$ $\rightarrow$ $N_2$$_{(g)}$ $+$ $4H_2O$$_{(l)}$; $\Delta r{H_1}^ \circ = - 818 \,kJ/mol$
$(ii)$ $N_2H_4$$_{(l)}$ $+$ $O_2$$_{(g)}$ $\rightarrow$ $N_2$$_{(g)}$ $+$ $2H_2O$$_{(l)}$; $\Delta r{H_2}^ \circ = - 622 \,kJ/mol$
$(iii)$ ${H_2}_{(g)}\,\, $+$ \,\,\frac{1}{2}\,{O_2}_{(g)}\,\, \to \,\,{H_2}O_{(l)}\,\,\,;\,\,{\Delta }r{H_3}^ \circ \, = \,\, - 285\,\,kJ/mol$
($373\, K$ તાપમાને અને $1$ બાર દબાણે પાણીની મોલર બાષ્પાયન એન્થાલ્પી $= 41\, kJ\, mol^{-1}$ તથા $R= 8.314 \, J-K^{-1}\, mol^{-1})$