Correct answer: 3. [tex] Mg^{2+}(aq) + 2 F^{-}(aq) --> MgF_{2}(s) [/tex]
The given chemical reaction is between ammonium fluoride and magnesium chloride to form magnesium fluoride and ammonium chloride.
The balanced chemical equation representing the reaction will be,
[tex] 2NH_{4}F (aq) + MgCl_{2}(aq) -->MgF_{2} (s) + 2NH_{4}Cl (aq) [/tex]
The complete ionic equation for the reaction: All the compounds soluble in water (aqueous) will split into ions, [tex] MgF_{2} [/tex] will not split into ions as it is insoluble in water.
[tex] 2 NH_{4}^{+}(aq) + 2 F^{-}(aq) + Mg^{2+}(aq) + 2 Cl^{-}(aq) --> MgF_{2}(s) + 2 NH_{4}^{+}(aq) + 2 Cl^{-}(aq) [/tex]
The net ionic equation will be:
[tex] Mg^{2+}(aq) + 2 F^{-}(aq) --> MgF_{2}(s) [/tex]
Here the spectator ions are [tex] NH_{4}^{+} and Cl^{-} [/tex]
