Precipitation Reaction Chemistry Example 4

Solution

1. 1
   Exchange ions: $\text{Pb}^{2+}$ + $\text{CrO}_4^{2-}$ → $\text{PbCrO}_4$ (insoluble yellow solid). $\text{Na}^+$ + anion of lead salt remain in solution.
2. 2
   Assuming lead nitrate: $\text{Pb(NO}_3)_2\text{(aq)} + \text{Na}_2\text{CrO}_4\text{(aq)} \rightarrow \text{PbCrO}_4\text{(s)}\downarrow + 2\text{NaNO}_3\text{(aq)}$.
3. 3
   The formation of the characteristic yellow precipitate ($\text{PbCrO}_4$, lead chromate) is a confirmatory test for $\text{Pb}^{2+}$ ions, since very few other cations form insoluble yellow chromates.