Em tham khảo nha :

\(\begin{array}{l}
a)\\
Fe + 2HCl \to FeC{l_2} + {H_2}\\
{n_{{H_2}}} = \dfrac{{0,448}}{{22,4}} = 0,02mol\\
{n_{Fe}} = 0,02 \times 56 = 1,12g\\
{n_{F{e_x}{O_y}}} = 2,56 - 1,12 = 1,44g\\
\% Fe = \dfrac{{1,12}}{{2,56}} \times 100\%  = 43,75\% \\
\% F{e_x}{O_y} = 100 - 43,75 = 56,25\% \\
b)\\
F{e_x}{O_y} + y{H_2} \to xFe + y{H_2}O\\
{m_{F{e_x}{O_y}}} = \dfrac{{12,8 \times 56,25}}{{100}} = 7,2g\\
{m_{F{e_d}}} = 12,8 - 7,2 = 5,6g\\
{m_{F{e_{td}}}} = 11,2 - 5,6 = 5,6g\\
{n_{F{e_{td}}}} = \dfrac{{5,6}}{{56}} = 0,1mol\\
{n_{F{e_x}{O_y}}} = \dfrac{{{n_{F{e_{td}}}}}}{x} = \dfrac{{0,1}}{x}\\
{M_{F{e_x}{O_y}}} = 7,2:\dfrac{{0,1}}{x} = 72x\,dvC\\
 \Rightarrow 56x + 16y = 72x\\
 \Rightarrow 16x - 16y = 0\\
y = 1 \Rightarrow x = 1\\
 \Rightarrow CTHH:FeO
\end{array}\)