\(\Delta {H_f} = - 46.0\,kJ/mol\)
\(H + H \leftrightarrow {H_2};\,\Delta {H_f} = - 436\,kJ/mol\)
\(N + N \leftrightarrow {N_2};\,\Delta {H_f} = - 712\,kJ/mol\)
\(\Delta {H_f}(N{H_3}) = \frac{1}{2}\Delta {H_{N - N}} + \frac{3}{2}\Delta {H_{H - H}} - \Delta {H_{N - H}}\)
\( - 46 = \frac{1}{2}( - 712) + \frac{3}{2}( - 436) - \Delta {H_{N - H}}\)
On calculation
\(\Delta {H_{N - H}} = - 964\,kJ/mol\)
$\Delta H_f^o\left( {CO} \right) = - 110.5\,kJ\,mo{l^{ - 1}};$
$\Delta H_f^o\left( {C{O_2}} \right) = - 393.5\,kJ\,mo{l^{ - 1}}$