\(a.Fe_2O_3+3H_2-^{t^o}\rightarrow2Fe+3H_2O\\ Fe_3O_4+4H_2-^{t^o}\rightarrow3Fe+4H_2O\\ Đặt:\left\{{}\begin{matrix}Fe_2O_3=x\left(mol\right)\\Fe_3O_4=y\left(mol\right)\end{matrix}\right.\\ Tacó:\left\{{}\begin{matrix}160x+232y=27,6\\3x+4y=0,5\end{matrix}\right.\\ \Rightarrow\left\{{}\begin{matrix}x=0,1\\y=0,05\end{matrix}\right.\\ \Rightarrow\%Fe_2O_3=57,97\%;\%Fe_3O_4=42,03\%\\ b.\Sigma n_{Fe}=2n_{Fe_2O_3}+3n_{Fe_3O_4}=0,35\left(mol\right)\\ \Rightarrow m_{Fe}=19,6\left(g\right)\)