\(n_{CO}=\dfrac{6.72}{22.4}=0.3\left(mol\right)\)
\(Fe_2O_3+3CO\underrightarrow{^{^{t^0}}}2Fe+3CO_2\)
\(n_{CO\left(dư\right)}=x\left(mol\right),n_{CO_2}=y\left(mol\right)\)
\(\Rightarrow x+y=0.3\left(1\right)\)
\(\overline{M}=18\cdot2=36\left(\dfrac{g}{mol}\right)\)
\(\Rightarrow28x+44y=36\cdot0.3=10.8\left(2\right)\)
\(\left(1\right),\left(2\right):x=y=0.15\)
\(m_{Fe_2O_3}=\dfrac{0.15}{3}\cdot160=8\left(g\right)\)