Mg + 2HCl → MgCl2 + H2 (1)
Fe + 2HCl → FeCl2 + H2 (2)
\(n_{HCl}=\dfrac{7,3}{36,5}=0,2\left(mol\right)\)
\(n_{H_2}=\dfrac{0,18}{18}=0,01\left(mol\right)\)
Theo PT1,2: \(\Sigma n_{HCl}pư=2\Sigma n_{H_2}=2\times0,01=0,02\left(mol\right)< 0,2\left(mol\right)\)
⇒ HCl dư