# Write the molecular, total, and ionic equation: Na2CrO4(aq) + Ni(NO3)2 (aq) , Na2CrO4(aq) +...

## Question:

Write the molecular, total, and ionic equation: Na2CrO4(aq) + Ni(NO3)2 (aq) , Na2CrO4(aq) + BaCl2(aq), Na2CrO4 (aq) + Pb(NO3)2 (aq) , Na2CrO4(aq) + Cu(NO3)2(aq) .

## Ionic reactions:

Precipitation reactions can occur when solutions of aqueous ionic compounds are mixed and an insoluble ionic compound forms. This insoluble compound is called the precipitate and is solid in the solution. There are three ways chemical equations are written to show these types of reactions. The first is the molecular equation where ionic compounds are shown as molecules and soluble compounds are shown as dissolved with an (aq) designation. In the total ionic equation, the aqueous species from the molecular equation are shown broken up into cations and anions. The net ionic reaction shows only the species that are involved in the precipitation reaction. Ions that are unchanged on either side of the reaction are removed.

We can datermine what precipitate we could make by switching the ion pairs in the reactants and identifying any possible insoluble compounds. This is made easier by remembering that 1A cations and nitrates are always soluble so there is only one possible match in each set of compounds. All of these examples include chromates, most chromates are insoluble:

1)

{eq}Na_2CrO_4(aq) + Ni(NO_3)_2 (aq) \rightarrow NiCrO_4(s) + 2NaNO_3(aq)\\ 2Na^+(aq)+ CrO_4^{2-}(aq) + Ni^{2+}(aq)+2NO_3^- (aq) \rightarrow NiCrO_4(s) + 2Na^+(aq)+2NO_3^- (aq)\\ CrO_4^{2-}(aq) + Ni^{2+}(aq) \rightarrow NiCrO_4(s) \\ {/eq}

2)

{eq}Na_2CrO_4(aq) + BaCl_2 (aq) \rightarrow BaCrO_4(s) + 2NaCl(aq)\\ 2Na^+(aq)+ CrO_4^{2-}(aq) + Ba^{2+}(aq)+2Cl^- (aq) \rightarrow BaCrO_4(s) + 2Na^+(aq)+2Cl^- (aq)\\ CrO_4^{2-}(aq) + Ba^{2+}(aq) \rightarrow BaCrO_4(s) \\ {/eq}

3)

{eq}Na_2CrO_4(aq) + Pb(NO_3)_2 (aq) \rightarrow PbCrO_4(s) + 2NaNO_3(aq)\\ 2Na^+(aq)+ CrO_4^{2-}(aq) + Pb^{2+}(aq)+2NO_3^- (aq) \rightarrow PbCrO_4(s) + 2Na^+(aq)+2NO_3^- (aq)\\ CrO_4^{2-}(aq) + Pb^{2+}(aq) \rightarrow PbCrO_4(s) \\ {/eq}

4)

{eq}Na_2CrO_4(aq) + Cu(NO_3)_2 (aq) \rightarrow CuCrO_4(s) + 2NaNO_3(aq)\\ 2Na^+(aq)+ CrO_4^{2-}(aq) + Cu^{2+}(aq)+2NO_3^- (aq) \rightarrow CuCrO_4(s) + 2Na^+(aq)+2NO_3^- (aq)\\ CrO_4^{2-}(aq) + Cu^{2+}(aq) \rightarrow CuCrO_4(s) \\ {/eq}