\(a,PTHH:Mg+2HCl\rightarrow MgCl_2+H_2\\ b,n_{Mg}=\dfrac{4,8}{24}=0,2\left(mol\right)\\ \Rightarrow n_{MgCl_2}=0,2\left(mol\right)\\ \Rightarrow m_{MgCl_2}=0,2\cdot95=19\left(g\right)\\ c,n_{H_2}=0,2\left(mol\right)\\ \Rightarrow V_{H_2\left(đktc\right)}=0,2\cdot22,4=4,48\left(l\right)\)