\(n_{Al_2O_3}=\dfrac{30,6}{102}=0,3mol\)
\(n_{MgO}=\dfrac{6}{40}=0,15mol\)
\(PTHH\left(1\right):Al_2O_3+3H_2SO_4\rightarrow Al_2\left(SO_4\right)_3+3H_2O\\ \: \: \: \: \: \: \: \: \: \: \: \: \: \left(2\right):MgO+H_2SO_4\rightarrow MgSO_4+H_2O\)
\(\Rightarrow n_{H_2SO_4}=\dfrac{0,3.3}{1}+\dfrac{0,15.1}{1}=1,05mol\)
\(m_{H_2SO_4}=1,05.98=102,9g\)