Zinc Oxide (ZnO)

ZnO is commonly known as philosopher’s wool or zinc white or china white.

 Preparation:

It can be obtained by heating zinc in air.

            2Zn + O2               →      2ZnO

            It can also be prepared by decomposition of zinc carbonate. Zinc nitrate, zinc sulphate, etc.

            ZnCO3               →          ZnO + CO2

            2Zn(NO3)2        →           2ZnO + 4NO2 + O2

            ZnSO4              →           ZnO + SO2

 

Properties:

It is light white amorphous solid which becomes yellow on heating and again on cooling.

When heated with cobalt nitrate, it gives a green compound known a Rinmanr’s green, It is a mixed oxide and is used as green pigment.

            2Co (NO3)2              →               2CoO + 4NO2 + O2

            ZnO + CoO                 →            CoZnO2

                                                            Cobalto zincate (Rinmann’s green)

ZnO is an amphoteric oxide. And can react with both acid and alkali forming saltand water.

It is insoluble in water but dissolves in acid giving respective salts.

 

Use:

·         It is used as pigment in making white colored paints.

·         It is used for surgical dressing. (Sterilizing agent).

 

·         It is used in preparation of Rinmann’s grice used as pigment.

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