d
ઉકેલ : \((i)\) \(C(s)+O_2(g) \rightarrow CO _2( g ) \quad \Delta H=-393.7 kJ mol ^{-1}\)

\((ii)\) \(H _2( g )+\frac{1}{2} O _2( g ) \rightarrow H _2 O ( g ), \quad \Delta H=-241.8 kJ mol ^{-1}\)

\((iii)\) \(2 C ( s )+2 H _2( g ) \rightarrow C_2 H_4( g ), \quad \Delta H=+52.3 kJ mol ^{-1}\)

આપણો હેતુ:

\(\begin{gathered}
  {C_2}{H_4}\,(g)\,\, + \,\,3{O_2}\,(g)\,\, \to \,\,2C{O_2}\,(g)\,\, + \,\,2{H_2}O\,(g),\,\,\Delta H\,\,\, = \,\,? \hfill \\
   \hfill \\ 
\end{gathered} \)

\(2\) \(×\) સમીકરણ \((i)\) + \(2\) \(×\) સમીકરણ \((ii)-\) સમીકરણ \((iii)\) આપેલ

\(\begin{gathered}
  {\text{2C}}\,\,{\text{(s)}}\,\, + \,\,{\text{2}}{{\text{O}}_{\text{2}}}\,{\text{(g)}}\,\,\,\,\,\,\,\,\,\, \to \,\,\,\,\,\,\,{\text{2C}}{{\text{O}}_{\text{2}}}\,{\text{(g)}} \hfill \\
  \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, + \,\,{{\text{O}}_{\text{2}}}\,{\text{(g)}}\,\, + \,\,{\text{2}}{{\text{H}}_{\text{2}}}\,{\text{(g)}}\,\,\,\,\,\, + \,\,{\text{2}}{{\text{H}}_{\text{2}}}{\text{O}}\,{\text{(g)}} \hfill \\
  \,\,\,\,\,\,\,\,{\text{ - }}\,{\text{2C}}\,\,{\text{(s)}}\,\,\,\,{\text{ - }}\,{\text{2}}{{\text{H}}_{\text{2}}}\,{\text{(g)}}\,\,\,\,\,\,\,{\text{ - }}\,{{\text{C}}_{\text{2}}}{{\text{H}}_{\text{4}}}\,{\text{(g)}} \hfill \\
  \,\,\,\,\,\,\,\,\,\underline {{\text{3}}{{\text{O}}_{\text{2}}}\,{\text{(g)}}\,\, \to \,\,\,\,{\text{2C}}{{\text{O}}_{\text{2}}}\,{\text{(g)}}\,\, + \,\,{\text{2}}{{\text{H}}_{\text{2}}}{\text{O}}\,{\text{(g)}}\,\,{\text{ - }}\,\,{{\text{C}}_{\text{2}}}{{\text{H}}_{\text{4}}}\,{\text{(g)}}} {\text{ }} \hfill \\
  \,or\,\,\,\,{{\text{C}}_{\text{2}}}{H_{4\,}}(g)\,\, + \,\,3{O_2}\,(g)\,\, \to \,\,2C{O_2}\,(g)\,\, + \,\,2{H_2}O\,(g) \hfill \\
  \Delta H\,\, = \,2( - 393.7)\,\, + \,\,2\,( - 241.8)\,\, - \,\,(52.3)\,\, = \,\, - \,\,1323.3\,\,kJ\,\,mo{l^{ - 1}} \hfill \\ 
\end{gathered} \)