\(n_{Mg}=\dfrac{24}{24}=1\left(mol\right)\)
PT: \(Mg+2HCl\rightarrow MgCl_2+H_2\)
a, \(n_{H_2}=n_{Mg}=1\left(mol\right)\Rightarrow V_{H_2}=1.22,4=22,4\left(l\right)\)
b, \(n_{HCl}=2n_{Mg}=2\left(mol\right)\Rightarrow C_{M_{HCl}}=\dfrac{2}{0,2}=10\left(M\right)\)