MgO+H2SO4\(\rightarrow\)MgSO4+H2O(1)
Al2O3+3H2SO4\(\rightarrow\)Al2(SO4)3+3H2O(2)
Al2O3+2NaOH\(\rightarrow\)2NaAlO2+H2O(3)
\(n_{H_2SO_4}=0,8mol\)
nNaOH=0,2mol
\(n_{Al_2O_3}=\dfrac{1}{2}n_{NaOH}=0,1mol\)
\(m_{Al_2O_3}=0,1.102=10,2g\)
\(n_{MgO}=n_{H_2SO_4}=0,8-0,1.3=0,5mol\)
mMgO=0,5.40=20g