\(Fe_3O_4+4H_2\rightarrow3Fe+4H_2O\)
\(HgO+H_2\rightarrow Hg+H_2O\)
\(n_{Fe3O4}=\frac{8,7}{232}=0,0375\left(mol\right)\)
\(n_{HgO}=\frac{33,45}{216}=0,15\left(mol\right)\)
\(\Rightarrow n_{H2}=0,375.4+0,15=0,3\left(mol\right)\)
\(2Al+3H_2SO_4\rightarrow Al_2\left(SO_4\right)_3+3H_2\)
\(\Rightarrow n_{Al}=0,2\left(mol\right)\)
\(\Rightarrow m_{Al}=0,2.27=5,4\left(g\right)\)