Answer:
Adding [tex]Na_2CO_3[/tex]
Explanation:
Adding [tex]Na_2CO_3[/tex]
1) [tex]Na_2CO_3 + CuCl_2 \longrightarrow CuCO_3 + 2 NaCl[/tex]
2) [tex]Na_2CO_3 + MgCl_2 \longrightarrow MgCO_3 + 2 NaCl[/tex]
The salt [tex]CuCO_3[/tex] is insoluble in water but, in the other hand, the [tex]MgCO_3[/tex] has a very good solubility.