Potassium manganate
Potassium manganate is a chemical compound. Its chemical formula is K2MnO4. It contains potassium and manganate ions.
| Potassium manganate | |
|---|---|
| |
| IUPAC name | Potassium manganate(VI) |
| Identifiers | |
| CAS number | |
| PubChem | |
| EC number | 233-665-2 |
| SMILES | [O-][Mn](=O)(=O)[O-].[K+].[K+ |
| Properties | |
| Molecular formula | K2MnO4 |
| Molar mass | 197.132 g/mol |
| Appearance | dark green crystals |
| Density | 2.78 g/cm3, solid |
| Melting point |
190 °C |
| Solubility in water | decomposes |
| Acidity (pKa) | 7.1 |
| Structure | |
| Crystal structure | isomorphous with K2SO4 |
| Coordination geometry |
tetrahedral anion |
| Hazards | |
| Main hazards | oxidizer |
| NFPA 704 |
0
1
1
OX
|
| R-phrases | 8-36/37/38 |
| S-phrases | 17-26-36/37/39 |
| Related compounds | |
| Related compounds | KMnO4 MnO2 K2CrO4 K2FeO4 |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |
Properties
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
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
Potassium manganate does not have many uses. It is mainly made when potassium permanganate is made.
Safety
Potassium manganate is a moderate oxidizing agent. When it is reduced, it can made black or brown stains on glass, clothing, or skin.