PTHH: \(Fe_2O_3+3H_2\xrightarrow[]{t^o}2Fe+3H_2O\)
Ta có: \(n_{Fe}=\dfrac{21}{56}=0,375\left(mol\right)\)
\(\Rightarrow n_{Fe_2O_3}=0,1875\left(mol\right)\) \(\Rightarrow m_{Fe_2O_3}=0,1875\cdot160=30\left(g\right)\)
\(n_{Fe}=\dfrac{21}{56}=0.375\left(mol\right)\)
\(\Rightarrow n_{Fe_2O_3}=\dfrac{0.375}{2}=0.1875\left(mol\right)\)
\(m=0.1875\cdot160=30\left(g\right)\)