Lead dioxide
IUPAC name	Lead dioxide Lead(IV) oxide
Other names	Plumbic oxide Plattnerite
Identifiers
CAS number	1309-60-0 Y
UN number	1872
RTECS number	OGO700000
Properties
Molecular formula	PbO2
Molar mass	239.2 g/mol
Appearance	black powder
Density	9.38 g/cm3
Melting point	290 ºC decomp.
Solubility in water	insoluble
Hazards
MSDS	ICSC 1001
EU Index	082-001-00-6
EU classification	Repr. Cat. 1/3 Harmful (Xn) Dangerous for the environment (N)
R-phrases	R61, R20/22, R33, R62, R50/53
S-phrases	S53, S45, S60, S61
Flash point	Non-flammable
Related compounds
Other cations	Carbon dioxide Silicon dioxide Germanium dioxide Tin dioxide
Related lead oxides	Lead(II) oxide Lead(II,IV) oxide
Related compounds	Thallium(III) oxide Bismuth(III) oxide
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Lead dioxide, PbO₂, also plumbic oxide and lead(IV) oxide, is an oxide of lead, with lead in oxidation state +4. It has a molar mass of 239.2 g/mol. It occurs in nature as the mineral plattnerite.

When hydrated, it forms plumbic hydroxide or lead(IV) hydroxide, Pb(OH)₄; given the formula, this is a mainly hypothetical compound.

Lead dioxide is amphoteric. Lead dioxide can dissolve in strong base to form plumbate ion, Pb(OH)₆²⁻. This can then form plumbate compounds. In acid conditions, it is typically reduced to lead(II) ion, Pb²⁺; lead(IV) ion, Pb⁴⁺, is not found in aqueous solution.

The most important use of lead dioxide is as the cathode of lead acid batteries. This arises from the anomalous metallic conductivity of PbO₂—TiO₂, ZrO₂, GeO₂, and SnO₂ are all insulators with a band gap around 3eV, however PbO₂ is a metallic conductor. This is thought to be due to anionic vacancies in the structure creating a formally mixed valent lead oxidation state.

A lead acid battery is based on the equilibrium between lead metal and lead dioxide in sulfuric acid.

Pb + PbO₂ + 2HSO₄⁻ + 2H⁺ → 2PbSO₄ + 2H₂O, E = +2.05 V

[edit] External links

• National Pollutant Inventory: Lead and Lead Compounds Fact Sheet

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