d
 \(\begin{gathered}
  \,{\text{(i)}}\,{{\text{C}}_{{\text{(S)}}}} + {O_{2(g)}} \to S{O_{2(g)}}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\Delta {H_{(i)}} =  - x\,\,kJ \hfill \\
  (ii)\,{H_{2(g)}} + \frac{1}{2}{O_{2(g)}} \to {H_2}{O_{(l)}}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\Delta {H_{(ii)}}\, =  - y\,kJ \hfill \\
  (iii)\,C{H_{4(g)}} + \frac{1}{2}{O_{2(g)}} \to \,C{O_{2(g)}} + 2{H_2}{O_{(l)}}\,\,\,\,\,\,\,\Delta {H_{(iii)}} =  - z\,\,kJ\, \hfill \\ 
\end{gathered} \)

હવે , \(CH_4\) ની  સજન - ઉષ્માનું  સમીકરણ \(C_{(S)} +2H_2\)\(_(g) \to CH_{4(g)}\), \(\Delta\, H\) = ?

હેસના નિયમ મુજબ સમીકરણ \( (i) × 1\), સમીકરણ \((ii) ×2 \)  , સમીકરણ \((iii)\) ને ઉલટાવી ત્રણેય સમીકરણનો  સરવાળો કરતાં ,

\(\Delta H = -x + 2(-y) + (+z)\, kJ\)