Chemistry of Zinc Oxide

Zinc Oxide is an important compound of zinc. It is also called as Philosopher’s wool because in the earlier days, it was prepared by heating the zinc dust in air which produces fumes of smoke which people supposed to be wool.

Preparation:

  • By roasting zinc ores:
    $$\ce{2ZnS + 3O2 ->[\text{excess}]2ZnO + 2SO2}$$
  •  From Zinc carbonate: $$\ce{ZnCO3 ->ZnO + CO2 }$$
  • By burning vapours of zinc:  $$\ce{2Zn(g) + O2->2ZnO}$$

Physical properties

  •  It is a yellow fibrous powder.
  • It is insoluble in water.
  • On heating, it becomes yellow and becomes white on cooling.

Chemical properties

a. Reaction with sulphuric acid: It gives zinc sulphate and hydrogen when reacted with sulphuric acid.

$$\ce{ZnO + H2SO4->ZnSO4 + H2O}$$

b. Reaction with sodium hydroxide: Zinc when reacted with sodium hydroxide gives sodium zincate.
$$\ce{ZnO + 2NaOH->Na2ZnO2 + H2O}$$

c. Reaction with carbon: Zinc react with carbon to give calcium silicate. $$\ce{ZnO + C->[\Delta]CaSiO3}$$

d. Reaction with water:  Zinc upon reacting with water at 39°C gives zinc hydroxide.

$$\ce{ZnO + H2O->Zn(OH)2 }$$

Uses of Zinc Oxide:

  •  It is used as pigment of paints, lacquer and enamel.
  • It is used as filter in rubber.
  • In the manufacture of glass and pottery glaze.
  • Used in filling cavities of teeth.

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