STD 11 - 3. Classification of elements and periodicity in properties — JEE STD 11 Science — Question

(consider complete conversion)

$\left. \begin{gathered}
  {\text{4N}}{{\text{H}}_{3(g)}}{\text{ + 5}}{{\text{O}}_{2(g)}} \to {\text{ 4N}}{{\text{O}}_{(g)}}{\text{ +  6}}{{\text{H}}_{\text{2}}}{{\text{O}}_{{\text{(l)}}}} \hfill \\
  {\text{2N}}{{\text{O}}_{(g)}}{\text{ + }}{{\text{O}}_{2(g)}} \to {\text{2N}}{{\text{O}}_{2(g)}} \hfill \\
  {\text{3N}}{{\text{O}}_{2(g)}}{\text{ +  }}{{\text{H}}_{{\text{ 2}}}}{{\text{O}}_{(l)}} \to {\text{2H N}}{{\text{O}}_{3(aq)}}{\text{ +  N}}{{\text{O}}_{(g)}} \hfill \\ 
\end{gathered}  \right|\begin{array}{*{20}{c}}
  {\Delta H(kJ)} \\ 
  { - 904} \\ 
  { - 112} \\ 
  { - 140} 
\end{array}$