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Some Insoluble Lead(II) Compounds

This page looks at the formation of some insoluble lead(II) compounds from aqueous lead(II) ions using precipitation reactions. It describes the reactions to form lead(II) hydroxide, lead(II) chloride, lead(II) iodide and lead(II) sulfate.

Because of the insolubility of so many lead(II) compounds, the usual source of lead(II) ions in solution is lead(II) nitrate solution – and that will be assumed in all the following examples.

Making lead(II) hydroxide

If a little sodium hydroxide solution is added to colourless lead(II) nitrate solution, a white precipitate of lead(II) hydroxide is produced.

\text{Pb}^{2+}_{(aq)} + 2OH^-_{(aq)} \longrightarrow \text{Pb}(OH)_{2(s)}

If more sodium hydroxide solution is added, the precipitate redissolves to give a colourless solution which might be called sodium plumbate(II) solution – but could be called by a lot of alternative names depending on exactly how the formula is written!

\text{Pb}(OH)_{2(s)} + 2OH^-_{(aq)} \longrightarrow {\text{Pb}O_2}^{2-}_{(aq)} + 2H_2O_{(l)}

Note: These equations are simplifications. You will get complexes formed involving hydroxide ions, but the formulae of these aren't very clear-cut. I am using these particular versions of the equations to keep them in line with the corresponding reaction between lead(II) oxide and sodium hydroxide solution on the oxides of Group 4 page – also a simplification!

Making Lead(II) chloride

Lead(II) chloride can be made as a white precipitate by adding a solution containing chloride ions to lead(II) nitrate solution. You could use things like sodium chloride solution to provide the chloride ions, but it is usually easier just to add some dilute hydrochloric acid.

\text{Pb}^{2+}_{(aq)} + 2\text{Cl}^-_{(aq)} \longrightarrow \text{Pb}\text{Cl}_{2(s)}

Note: If you add concentrated hydrochloric acid to excess, the lead(II) chloride precipitate will dissolve again. Complex ions like PbCl42- are produced, and these are soluble in water.

Making Lead(II) iodide

If you add colourless potassium iodide solution (or any other source of iodide ions in solution) to a solution of lead(II) nitrate, a bright yellow precipitate of lead(II) iodide is produced.

\text{Pb}^{2+}_{(aq)} + 2I^-_{(aq)} \longrightarrow \text{Pb}I_{2(s)}

Making Lead(II) sulfate

Adding a source of aqueous sulfate ions to a solution of lead(II) nitrate results in a white precipitate of lead(II) sulfate. The easiest thing to add is usually dilute sulfuric acid – but any other soluble sulfate would do.

\text{Pb}^{2+}_{(aq)} + {SO_4}^{2-}_{(aq)} \longrightarrow \text{Pb}SO_{4(s)}

Questions to test your understanding

Questions on the formation of insoluble lead compounds Answers