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| Lead dioxide | |
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| IUPAC name | lead(IV) oxide |
| Other names | plumbic oxide |
| Identifiers | |
| CAS number | 1309-60-0 |
| Properties | |
| Molecular formula | PbO2 |
| Molar mass | 239.2 g/mol |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references |
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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.
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
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- This page was last modified on 1 November 2008, at 17:03.
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