Question

Manganese dioxide is ______ in colour.
A) Black
B) Blue
C) Brown
D) Green

Answer 1

Manganese dioxide is an inorganic compound. The molecular formula of manganese dioxide is
${\text{Mn}}{{\text{O}}_{\text{2}}}$. It occurs naturally in pyrolusite ore.

Complete answer:
Manganese is transition metal. It is represented by the symbol ${\text{Mn}}$. The name manganese dioxide indicates that one manganese atom combines with two oxygen atoms. So the molecular formula of manganese dioxide is ${\text{Mn}}{{\text{O}}_{\text{2}}}$.
In manganese dioxide, each oxygen atom forms a double bond with the central manganese atom. The principal ore of manganese dioxide is pyrolusite. We can extract the manganese by reducing the manganese dioxide with carbon.

The physical properties of manganese dioxide are:

Odour: It is odourless
Appearance: It is black solid
Solubility: It is insoluble in water
Melting point : $535^\circ {\text{C}}$
Thus, manganese dioxide is back in colour.

Additional Information:
(a) Chemical properties:
i) It reacts with potassium hydroxide in presence of oxygen and forms potassium permanganate.
ii) It reacts with aluminium forming aluminium oxide and water.

(b) Used of manganese dioxide:
i) Used as a catalyst in the oxidation reaction.
ii) Used as an important component in batteries.
iii) Used in ceramic industries.
iv) Used in glassmaking.
v) It is the only important compound of quadripositive manganese.

Hence, the correct answer is option (A) Black.

Note: Manganese dioxide having formula ${\text{Mn}}{{\text{O}}_{\text{2}}}$ is black colour solid. The natural source of Manganese dioxide Pyrolusite ore. Manganese dioxide is thermally stable.