`a,`
`n_(H_2)=\frac{2,24}{22,4}=0,1(mol)`
`Mg+2HCl->MgCl_2+H_2`
`0,1` `0,2` `0,1` `0,1`
`MgO+2HCl->MgCl_2+H_2O`
`0,1` `0,2` `0,1`
`m_(Mg)=0,1.24=2,4(g)`
`=>m_(MgO)=6,4-2,4=4(g)`
`=>n_(MgO)=\frac{4}{40}=0,1(mol)`
`b,`
`m_(HCl)=0,4.36,5=14,6(g)`
`=>m_(dd HCl)=\frac{14,6}{7,3%}=200(g)`
`c,`
`m_(MgCl_2)=0,2.95=19(g)`
`m_(dd)=6,4+200-0,2=206,2(g)`
`C%_(MgCl_2)=\frac{19}{206,2}.100=9,214%`