Potassium manganate
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| Names | ||
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| IUPAC name
Potassium manganate(VI)
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| Identifiers | ||
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3D model (JSmol)
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| ECHA InfoCard | 100.030.592 | |
| EC Number |
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PubChem CID
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CompTox Dashboard (EPA)
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| Properties | ||
| K2MnO4 | ||
| Molar mass | 197.132 g/mol | |
| Appearance | dark green crystals | |
| Density | 2.78 g/cm3, solid | |
| Melting point | 190 °C | |
| decomposes | ||
| Acidity (pKa) | 7.1 | |
| Structure | ||
| isomorphous with K2SO4 | ||
| tetrahedral anion | ||
| Hazards | ||
| Main hazards | oxidizer | |
| NFPA 704 |
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| R-phrases | 8-36/37/38 | |
| S-phrases | 17-26-36/37/39 | |
| Related compounds | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | ||
 verify (what is   ?)
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| Infobox references | ||
Potassium manganate is a chemical compound. Its chemical formula is K2MnO4. It contains potassium and manganate ions.
Properties
[change | change source]Potassium manganate is a green solid. It can disproportionate into potassium permanganate and manganese(IV) oxide. This happens in acidic pH. This reaction, because of its color change, is known as a "chemical chameleon".
Preparation
[change | change source]It is made by reacting manganese(IV) oxide with very hot potassium hydroxide. Sometimes oxygen or potassium nitrate is used as the oxidizing agent. This makes potassium manganate. Normally the potassium manganate is converted to potassium permanganate. Potassium permanganate is more common. Potassium iodide can reduce potassium permanganate to potassium manganate. It can also be made by reacting hot potassium permanganate with potassium hydroxide. This makes oxygen and potassium manganate.
Uses
[change | change source]Potassium manganate does not have many uses. It is mainly made when potassium permanganate is made.
Safety
[change | change source]Potassium manganate is a moderate oxidizing agent. When it is reduced, it can made black or brown stains on glass, clothing, or skin.