Lead sulfide (PbS) is an insoluble metal sulfide in water. It forms a black precipitate in the water. Though PbS is not solble in water, it dissolve in nitric acid. Solubility data proves that PbS is a precipitate in water.
Content
Lead sulfide (PbS) is an insoluble metal sulfide and deposit as a black precipitate in the water.
In physical chemistry, we can mention the solubility value to identify the solubility of a compound. This solubility value can be expressed per 100 ml of water. Then you can calculate, how much will dissolve in a certain amount of volume. At 200C temperature, solubility of Lead sulfide is 0.01244 g/100 mL
Because PbS is insoluble in water, solubility product value of PbS should be a very small value. As we have guessed that solubility product of PbS is 9.04 * 10-29 mol2 dm-6.
Send hydrogen sulfide (H2S) gas to a Lead nitrate solution. It will give black colour PbS precipitate. Usually, lead sulfide is precipitated in an slightly acidified medium due to its' lower solubility product value.
When hot dilute HCl acid is added to a lead(II) sulfide, hydrogen sulfide gas is formed. Therefore, PbS precipitate will be destroyed. But, when lead +2 ions and chloride ions exist in an aqueous solution, Lead chloride (PbCl2) is deposited as a white precipitate. So instead of PbS, you will finish with white colour PbCl2 precipitate.
If you add more hot HCl acid, white precipitate dissolved and give a colorless solution.
PbS reacts with hydrogen peroxide and sulfide ion is oxidized to sulfate ion. Again, Pb2+ ion and sulfate ion combines to form lead sulfate (PbSO4) white precipitate.
Questions asked by students
As PbS, PbSO4, PbCO3, PbCl, PbBr2, PbI2 are insoluble in water.
No, though PbS is black, PbSO4, PbCO3, PbCl are white color insoluble precipitates. PbBr2 is a cream color precipitate. PbI2 form a yellow color precipitate in water.