Manganese dioxide - MnO2

What is Manganese dioxide?

  • Manganese dioxide is a black-brown solid that 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.

Table of Contents

Impure manganese can be made by reducing manganese dioxide with carbon. It is the only important compound of quadripositive manganese.

Other names – 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 MnO2

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

4MnO2 + 4KOH + 3O2 → 4KMnO4 + 2H2O

    • Manganese dioxide reacts with aluminium forming aluminium oxide and water. The chemical equation is as below.

3MnO2 + 4Al → 2Al2O3 + 3Mn + heat

When MnO2 is fused with KOH

When blackish coloured compound MnO2 is fused with KOH in presence of air, it produces a dark green coloured compound potassium manganate.

2MnO2​ + 4KOH + O2 → 2K2MnO4 + 2H2O

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 glassmaking to remove the green tint caused by iron impurities.
  • Used as an important component in batteries. In the Leclanche cell, the positive electrode carbon, is surrounded by manganese dioxide and carbon.

Frequently Asked Questions – FAQs


What are the uses of manganese dioxide?

MnO2 is primarily used as a part of dry cell batteries: alkaline batteries and the so-called Leclanché cell, or zinc–carbon batteries. For this application, approximately 500,000 tons are consumed annually. Many industrial uses include the use of MnO2 in ceramics and glass-making as an inorganic pigment.


Is MnO2 a catalyst?

Manganese dioxide, a compound with the formula MnO2, is used as a catalyst for rapid oxidation of dissolved iron and manganese, present in the form of ferrous and manganese powder, in contact filters. These salts are oxidised by dissolved oxygen to an insoluble ferric and manganic acid.


How is manganese dioxide formed?

By oxidation of the elemental manganese: elemental manganese reacts with oxygen in the environment to form MnO2. Because of this reaction, elemental manganese does not exist in nature – it is usually found as manganese dioxide in nature.


Is manganese dioxide harmful to humans?

Harmful if inhaled or swallowed. It may cause eye, skin, and respiratory tract irritation. May cause central nervous system effects. Inhalation of fumes may cause metal-fume fever.


What are the symptoms of manganese toxicity?

Manganese toxicity can result in a permanent neurological disorder known as manganism with symptoms that include tremors, difficulty walking, and facial muscle spasms. These symptoms are often preceded by other lesser symptoms, including irritability, aggressiveness, and hallucinations.

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