Manganese dioxide - MnO<sub>2</sub>

What is Manganese dioxide?

Manganese dioxide is a black-brown solid occurs naturally with the formula MnO2. Manganese dioxide (MnO2), known as pyrolusite when found in nature, is the most plentiful of all the manganese compounds. The principal ore of manganese dioxide is pyrolusite which was known to the ancients as a pigment. Impure manganese can be made by reducing manganese dioxide with carbon. It is the only important compound of quadripositive manganese.

Other name – dioxomanganese, Manganese(IV) oxide

MnO2

Manganese dioxide

Density

5.03 g/cm³

Molecular Weight/ Molar Mass

86.9368 g/mol

Covalently bonded unit

1

Melting Point

535 °C

Chemical Formula

MnO2

Manganese dioxide Structure – MnO2

Manganese dioxide

Physical Properties of Manganese dioxide – MnO2

Odour

Odourless

Appearance

Brown-black solid

Complexity

18.3

Oxidation number

+4

Hydrogen Bond Acceptor

2

Solubility

Insoluble in water

Chemical Properties of Manganese dioxide – MnO2

  • Manganese dioxide reacts with potassium hydroxide in the presence of oxygen forms potassium permanganate.
  • 4MnO2 + 4KOH + 3O2 → 4KMnO4 + 2H2O

  • Manganese dioxide reacts with aluminum forming aluminium oxide and water. The chemical equation is as below.
  • MnO2 + Al → Al2O3 + Mn

Uses of Manganese dioxide – MnO2

  • Used in Ceramic Industries for making glass practically all the raw materials used in glass contain some iron, usually in the form of ferric oxide.
  • Ores of manganese are not ‘active’ for direct use in dry cell manufacture and many of them need to be activated by physical or chemical treatment.
  • Used in glass making to remove the green tint caused by iron impurities.
  • Used as an important component in batteries. The Leclanche cell the positive electrode carbon is surrounded by manganese dioxide and carbon.

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