Bạn tham khảo:
$\underbrace{\left \{ {{Mg=a(mol)} \atop {Ca}=b(mol)} \right.}_{m_{hh}=24a+40b=8,8(1)}\xrightarrow{HCl}$ $\left \{ {{MgCl_2=a(mol)} \atop {CaCl_2}=b(mol)} \right. \xrightarrow{CO_3^{2-}}\underbrace{ \left \{ {{MgCO_3↓=a(mol)} \atop {CaCO_3↓=b(mol)}} \right.}_{m↓=84a+100b=26,8(2)}$
$(1)(2)$
$a=0,2$
$b=0,1$
$m_{Mg}=0,2.24=4,8(g)$
BT $Cl$
$n_{HCl}=0,2.2+0,1.2=0,6(mol)$
$CM_{HCl}=\frac{0,6}{0,5}=1,2M$