Lead, Pb²⁺

Most common oxidation states: +2, +4

M.P. 328^o

B.P. 1750^o

Density 11.35 g/cm³

Characteristics: Lead is a soft metal having little tensile strength, and it is the densest of the common metals excepting gold and mercury. It has a metallic luster when freshly cut but quickly acquires a dull color when exposed to moist air.

Characteristic reactions of Pb²⁺:

The +2 oxidation state is the more stable state.

Chloride Ion:

Soluble chlorides, such as hydrochloric acid, precipitate white lead chloride from Pb²⁺ solutions, when the solutions are not too dilute:

Lead chloride is a slightly soluble salt, with a solubility of 10 g/L at 20^o. The solubility of PbCl₂ increases very rapidly as the temperature rises. At 100^o it has a solubility of 33.5 g/L. However, PbCl₂ precipitates very slowly, particularly when other ions that form insoluble chlorides are not present. The precipitation can be speeded up by vigorously rubbing the inside of the test tube with a stirring rod. Even then the precipitate may not form until 3 to 5 minutes after mixing the solutions. PbCl₂ dissolves in excess chloride ion as a result of the formation of a complex ion, tetrachloroplumbate(II) ion:

Sulfate Ion:

Soluble sulfates, including dilute sulfuric acid, precipitate white lead sulfate, which is much less soluble than lead chloride:

PbSO₄ dissolves in concentrated solutions of hydroxide or acetate ions.

The lead acetate, though only slightly dissociated, is soluble.

Aqueous Ammonia:

Lead(II) ion reacts with aqueous ammonia to precipitate a white basic salt, Pb₂O(NO₃)₂, rather than the expected lead(II) hydroxide:

The basic salt is insoluble in excess ammonia.

Sodium Hydroxide:

Sodium hydroxide precipitates lead(II) hydroxide, which dissolve with excess hydroxide:

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