\(a) Fe + 2HCl \to FeCl_2 + H_2\\ b) n_{H_2} = n_{Fe} = \dfrac{8,4}{56} = 0,15(mol)\\ V_{H_2} = 0,15.22,4 = 3,36(lít)\\ n_{HCl} = 2n_{H_2} = 0,3(mol)\ m_{HCl} = 0,3.36,5 = 10,95(gam)\)
\(n_{Fe}=\dfrac{8.4}{56}=0.15\left(mol\right)\)
\(Fe+2HCl\rightarrow FeCl_2+H_2\)
\(0.15......0.3..................0.15\)
\(m_{HCl}=0.3\cdot36.5=10.95\left(g\right)\)
\(V_{H_2}=0.15\cdot22.4=3.36\left(l\right)\)