\(n_{hh}^{} = \frac{{5,6}}{{22,4}} = 0,25\;{\text{mol}}\)

\(n_{NO}^{} + n_{N_2^{}}^{} = 0,25\)

\(30.n_{NO}^{} + 28.n_{N_2^{}}^{} = 7,2\)

\( \to n_{NO}^{} = 0,1\;{\text{mol; n}}_{N_2^{}}^{} = 0,15{\text{ mol}}\)

\({N^{ + 5}} + 3e \to {N^{ + 2}}\)

\({\text{         0}}{\text{,3      0}}{\text{,3}}\)

\(2{N^{ + 5}} + 10e \to N_2^0\)

\({\text{         1}}{\text{,5         0}}{\text{,15}}\)

\({\text{n}}_{e_{Cho}^{}}^{} = n_{e_{Nhan}^{}}^{} = 1,8\;{\text{mol}}\)

\({{\text{X}}^0} \to {X^{n + }} + ne\)

\({\text{ }}\frac{{1,8}}{n}{\text{            1}}{\text{,8}}\)

\({\text{M}}_X^{} = \frac{{16,2}}{{\frac{{1,8}}{n}}} = 9n\)

\( \to n = 3 \to X = 27g/mol(Al)\)

\(\begin{array}{l}
Dat\,hoa\,tri\,X\,la\,n\\
\begin{cases} n_{NO}+n_{N_2}=\frac{5,6}{22,4}=0,25\\ 30n_{NO}+28n_{N_2}=7,2 \end{cases}\\
\to\begin{cases}n_{NO}=0,1(mol)\\ n_{N_2}=0,15(mol)\end{cases}\\
X^0\to X^n+ne\\
N^{+5}+3e\to N^{+2}\\
2N^{+5}+10e\to N_2^0\\
Bao\,toan\,e:\,n.n_X=3n_{NO}+10n_{N_2}=1,8(mol)\\
\to \frac{16,2n}{M_X}=1,8\\
\to M_X=9n\\
\to n=3;M_X=27(g/mol)\\
\to X:\,nhom\,(Al)
\end{array}\)