Lead dioxide

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Lead (IV) oxide, PbO₂, also plumbic oxide and lead dioxide, 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.

Lead dioxide is a somewhat strong oxidizer. With many reducing agents, it can produce lead(II) ion, Pb²⁺, or plumbous hydroxide, Pb(OH)₂.

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 - each Oxygen that is removed leaves behind two electrons which go into the conduction band.

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

External links

• National Pollutant Inventory: Lead and Lead Compounds Fact Sheet

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Last updated on Thursday March 13, 2008 at 03:58:11 PDT (GMT -0700)
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