JEE Main 2024 — Coordination Compounds Question with Solution

Lead chromate ( $${\mathrm{PbCrO}}_4$$ ) dissolves in hot NaOH solution to form products due to a chemical reaction. The reaction involves the formation of a compound where lead ( $$\mathrm{Pb}$$ ) is coordinated by hydroxide ions ( $${\mathrm{OH}}^{-}$$ ).

The balanced chemical reaction is:

$${\mathrm{PbCrO}}_4+4\mathrm{NaOH}(hot,excess)\to {\left[\mathrm{Pb}(\mathrm{OH}{)}_4\right]}^{2-}+{\mathrm{Na}}_2{\mathrm{CrO}}_4$$

In this reaction, lead forms a dianionic complex ( $${\left[\mathrm{Pb}(\mathrm{OH}{)}_4\right]}^{2-}$$ ) with hydroxide ions. This indicates that the lead is in the center of a complex with a coordination number of four, meaning it is directly bound to four hydroxide ions. Therefore, the correct description of the product formed with lead is a dianionic complex with a coordination number of four.