PTHH: \(Fe+2HCl\rightarrow FeCl_2+H_2\uparrow\)
a) Ta có: \(n_{Fe}=\dfrac{8,4}{56}=0,15\left(mol\right)=n_{H_2}\) \(\Rightarrow V_{H_2}=22,4\cdot0,15=3,36\left(l\right)\)
b) Theo PTHH: \(n_{HCl}=2n_{Fe}=0,3mol\)
\(\Rightarrow m_{ddHCl}=\dfrac{0,3\cdot36,5}{7,3\%}=150\left(g\right)\)