\(n_{Mg}=\dfrac{7,2}{24}=0,3\left(mol\right)\\ n_{HCl}=\dfrac{18,25}{36,5}=0,5\left(mol\right)\)
PTHH: \(Mg+2HCl\rightarrow MgCl_2+H_2\)
LTL: \(0,3>\dfrac{0,5}{2}\rightarrow\) Mg dư
\(n_{H_2}=\dfrac{1}{2}n_{HCl}=\dfrac{1}{2}.0,5=0,25\left(mol\right)\\ \rightarrow V_{H_2}=0,25.22,4=5,6\left(l\right)\)