a
\(\begin{array}{l}
\\
{\rm{C}}\,\,\,\,\,\,\,\,\,\,\,\,{\rm{:}}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{\rm{H}}\,\,\,\,\,\,\,\,\,\,\,\,{\rm{:}}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{\rm{N}}\\
\frac{{\rm{9}}}{{{\rm{12}}}}\,\,\,\,\,\,\,\,\,\,:\,\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{1}{1}\,\,\,\,\,\,\,\,\,\,\,\,\,\,:\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{{3.5}}{{14}}\\
0.75\,\,\,\,\,\,\,:\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,1\,\,\,\,\,\,\,\,\,\,\,\,\,:\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,0.25\,\,\,\,\,\,\\
3\,\,\,\,\,\,\,\,\,\,\,\,\,:\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,4\,\,\,\,\,\,\,\,\,\,\,:\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,1\,\,\\
{C_3}{H_4}N\,\\
n = \frac{{108}}{{54}} = 2\,\,\,\,\,\,\,\,M.F. = {C_6}{H_8}{N_2}\,\,\,
\end{array}\)