\(n_{H_2}=\dfrac{V}{22,4}=\dfrac{8,4}{22,4}=0,375\left(mol\right)\)
\(pthh:Fe_2O_3+3CO\overset{t^0}{\rightarrow}2Fe+3CO_2\left(1\right)\\ Fe+H_2SO_4\rightarrow FeSO_4+H_2\left(2\right)\)
Theo \(pthh\left(1\right):n_{Fe}=n_{H_2}=0,375\left(mol\right)\)
\(\Rightarrow m_{Fe}=n\cdot M=0,375\cdot56=21\left(g\right)\)
\(\text{Theo }pthh\left(2\right):n_{Fe_2O_3}=\dfrac{1}{2}n_{Fe}=\dfrac{1}{2}\cdot0,375=0,1875\left(mol\right)\)
\(\Rightarrow m_{Fe_2O_3}=n\cdot M=0,1875\cdot160=30\left(g\right)\)