a,
\(n_{H2}=0,3\left(mol\right)\)
\(2M+2nHCl\rightarrow2MCln+nH2\)
\(\rightarrow n_M=\frac{0,6}{n}\left(mol\right)\)
\(\rightarrow M_M=\frac{54n}{0,6}=9n\)
\(n=3\rightarrow M=27\left(TM\right)\)
Vậy M là Al
b,
\(n_{HCl}=2n_{H2}=0,6\left(mol\right)\)
\(\rightarrow m_{HCl}=21,9\left(g\right)\)
\(\rightarrow m_{dd_{HCl}}=21,9:20\%=109,5\left(g\right)\)
\(m_{dd_{spu}}=5,4+109,5-0,3.2=114,3\left(g\right)\)
\(n_{AlCl3}=n_{Al}=0,2\left(mol\right)\)
\(\rightarrow m_{AlCl3}=26,7\left(g\right)\)