12. barium nitrate solution and a potassium fluoride solution are combined and a precipitate…

Explanation:

Step1: Determine the products

The reaction between barium nitrate ($\ce{Ba(NO3)2}$) and potassium fluoride ($\ce{KF}$) is a double - displacement reaction. The products are barium fluoride ($\ce{BaF2}$) and potassium nitrate ($\ce{KNO3}$). According to solubility rules, $\ce{BaF2}$ is insoluble and will form a precipitate. The molecular equation is $\ce{Ba(NO3)2(aq)+2KF(aq)\rightarrow BaF2(s) + 2KNO3(aq)}$.

Step2: Write the complete ionic equation

In solution, $\ce{Ba(NO3)2}$ dissociates into $\ce{Ba^{2 + }(aq)}$ and $2\ce{NO3^{-}(aq)}$, $\ce{KF}$ dissociates into $2\ce{K^{+}(aq)}$ and $2\ce{F^{-}(aq)}$, $\ce{KNO3}$ dissociates into $2\ce{K^{+}(aq)}$ and $2\ce{NO3^{-}(aq)}$, and $\ce{BaF2}$ remains as a solid. So the complete ionic equation is $\ce{Ba^{2 + }(aq)+2NO3^{-}(aq)+2K^{+}(aq)+2F^{-}(aq)\rightarrow BaF2(s)+2K^{+}(aq)+2NO3^{-}(aq)}$.

Step3: Write the net ionic equation

Spectator ions are ions that appear on both sides of the complete ionic equation. Here, $\ce{K^{+}}$ and $\ce{NO3^{-}}$ are spectator ions. Canceling them out gives the net ionic equation $\ce{Ba^{2 + }(aq)+2F^{-}(aq)\rightarrow BaF2(s)}$.

Step4: Identify spectator ions

The spectator ions are $\ce{K^{+}(aq)}$ and $\ce{NO3^{-}(aq)}$ as they do not participate in the formation of the precipitate.

Answer:

Molecular: $\ce{Ba(NO3)2(aq)+2KF(aq)\rightarrow BaF2(s) + 2KNO3(aq)}$ Complete Ionic: $\ce{Ba^{2 + }(aq)+2NO3^{-}(aq)+2K^{+}(aq)+2F^{-}(aq)\rightarrow BaF2(s)+2K^{+}(aq)+2NO3^{-}(aq)}$ Net Ionic: $\ce{Ba^{2 + }(aq)+2F^{-}(aq)\rightarrow BaF2(s)}$ Spectator ions: $\ce{K^{+}(aq), NO3^{-}(aq)}$