\(n_{Al_2\left(SO_4\right)_3}=\frac{m_{Al_2\left(SO_4\right)_3}}{M_{Al_2\left(SO_4\right)_3}}=\frac{34,2}{342}=0,1\left(mol\right)\)
\(m_{Al}=n_{Al_2\left(SO_4\right)_3}.\left(M_{Al}.2\right)=0,1.\left(27.2\right)=5,4\left(g\right)\)
\(m_S=n_{Al_2\left(SO_4\right)_3}.\left(M_S.3\right)=0,1.\left(32.3\right)=9,6\left(g\right)\)
\(m_O=n_{Al_2\left(SO_4\right)_3}.\left(M_O.12\right)=0,1.\left(16.12\right)=19,2\left(g\right)\)