\(n_{H_2}=\dfrac{2,36}{22,4}=\dfrac{59}{560}\left(mol\right)\\ 2Al+3H_2SO_4\rightarrow Al_2\left(SO_4\right)_3+3H_2\\Al_2O_3+3H_2SO_4\rightarrow Al_2\left(SO_4\right)_3+3H_2O\\ n_{Al}=\dfrac{2}{3}.\dfrac{59}{560}=\dfrac{59}{840}\left(mol\right)\\ \Rightarrow\%m_{Al}=\dfrac{\dfrac{59}{840}.27}{50}.100\approx3,793\%\\ \Rightarrow\%m_{Al_2O_3}\approx96,207\%\)