\(n_{MgO}=a\left(mol\right),n_{Fe_2O_3}=b\left(mol\right)\)
\(m=40a+160b=12\left(g\right)\left(1\right)\)
\(MgO+H_2SO_4\rightarrow MgSO_4+H_2O\)
\(Fe_2O_3+3H_2SO_4\rightarrow Fe_2\left(SO_4\right)_3+3H_2O\)
\(m_{Muối}=120a+400y=32\left(g\right)\left(2\right)\)
\(\left(1\right),\left(2\right):a=0.1,b=0.05\)
\(\%MgO=\dfrac{0.1\cdot40}{12}\cdot100\%=33.33\%\)
\(\%Fe_2O_3=66.67\%\)
\(m_{dd}=12+200=212\left(g\right)\)
\(C\%_{MgSO_4}=\dfrac{0.1\cdot120}{212}\cdot100\%=5.66\%\)
\(C\%_{Fe_2\left(SO_4\right)_3}=\dfrac{0.05\cdot400}{212}\cdot100\%=9.42\%\)