Lead(II) hydroxide, Pb(OH)
2, is a
hydroxide
Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water ...
of
lead
Lead is a chemical element with the Symbol (chemistry), symbol Pb (from the Latin ) and atomic number 82. It is a heavy metals, heavy metal that is density, denser than most common materials. Lead is Mohs scale of mineral hardness#Intermediate ...
, with lead in
oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. ...
+2. In 1964 it was believed that such a simple compound did not exist, as
lead basic carbonate (2PbCO
3·Pb(OH)
2) or
lead(II) oxide
Lead(II) oxide, also called lead monoxide, is the inorganic compound with the molecular formula lead, Pboxide, O. PbO occurs in two Polymorphism (materials science), polymorphs: litharge having a tetragonal crystal system, tetragonal crystal struc ...
(PbO) was encountered where lead hydroxide was expected. This has been a subject of considerable confusion in the past. However, subsequent research has demonstrated that lead(II) hydroxide does indeed exist as one of a series of lead hydroxides.
Preparation
When a hydroxide is added to a solution of a lead(II) salt, a hydrated lead oxide PbO·xH
2O (with x < 1) is obtained. Careful
hydrolysis
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile.
Biological hydrolysis ...
of
lead(II) acetate
Lead(II) acetate (Pb(CH3COO)2), also known as lead acetate, lead diacetate, plumbous acetate, sugar of lead, lead sugar, salt of Saturn, or Goulard's powder, is a white crystalline chemical compound with a slightly sweet taste. Like many other le ...
solution yields a crystalline product with a formula 6PbO·2H
2O = Pb
6O
4(OH)
4.
[Von Egon Wiberg, Nils Wiberg, Arnold Frederick Holleman, "Inorganic Chemistry", Academic Press, 200]
(Google books)
This material is a cluster compound, consisting of an octahedron of Pb centers, each face of which is capped by an oxide or a hydroxide. The structure is reminiscent of the Mo
6S
8 subunit of the
Chevrel phases.
Reactions
In solution, lead(II) hydroxide is a somewhat weak
base, forming lead(II)
ion, Pb
2+, under weakly
acidic
In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a s ...
conditions. This
cation
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...
hydrolyze
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile.
Biological hydrolysis ...
s and, under progressively increasing
alkaline
In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a ...
conditions, forms Pb(OH)
+, Pb(OH)
2(aqueous), Pb(OH)
3−, and other
species
In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...
, including several polynuclear species, e.g., Pb
4(OH)
44+, Pb
3(OH)
42+, Pb
6O(OH)
64+.
Lead hydrate
The name Lead hydrate has sometimes been used in the past but it is unclear whether this refers to Pb(OH)
2 or PbO·xH
2O.
References
External links
Case Studies in Environmental Medicine - Lead Toxicity
{{Hydroxides
Hydroxides
Lead(II) compounds