`A+2HCl->ACl_2+H_2`
`n_{HCl}=0,3.1=0,3mol`
`HCl+NaOH->NaCl+H_2O`
`n_{NaOH}=0,5.0,1=0,05mol`
`n_{HCl}=n_{NaOH}`
`->n_{HCl}=0,3-0,05=0,25mol`
`n_{A}=1/2 .0,25=0,125mol`
`M_A=3/(0,125)=24`
`A:Mg`
`Mg+2HCl->MgCl_2+H_2`
`mdd_{HCl}=1,025.300=307,5g`
`mdd_{spu}=3+307,5-0,125.2=310,25g`
`n_{MgCl_2}=n_{Mg}=0,125mol`
`%m_{MgCl_2}=(0,125.(24+35,5.2))/(310,25%)=3,83%`
