Hseb Notes - Chemistry XI - Oxides

Oxides

Binary compounds of oxygen with other elements ( metals or non-metals ) are called oxides.
Depending upon the acidic and basic behavior and structural consideration oxides are classified as follows:
  • Acidic oxides :

Oxides of non-metals which combine with water to give acids and are neutralized by bases or basic oxides are called acidic oxides. They are oxides are also called anhydride of inorganic acids.

Examples of acidic oxides are CO2, SO3, SO2, N2O5, P2O5, Cl2O7 etc. 


CO2 + H2O -------------> H2CO3
CO2 + 2NaOH -------------> Na2CO3 + H2O
CO2 + Na2O -------------> Na2CO3

  • Basic oxides :

Oxides of metals which combine with water to form bases and with acids or acidic oxides to give salt are called basic oxides.

Examples of basic oxides are Na2O, MgO, CaO, FeO, CuO, BaO etc.

MgO + H2O -------------> Mg(OH)2
MgO + 2HCl -------------> MgCl2 + H2O
MgO + CO2 -------------> MgCO3
  • Neutral oxides :

These are the oxides which neither forms salt with an acid nor with a base and they do not combine with water to form acid or base.

Examples of neutral oxides are CO, H 20, NO, N2O etc.

  • Amphoteric oxides :

These are the oxides which are both acidic and basic in nature they combine with acids as well as bases to form salt and water. Generally, the oxides of Be, Al, Zn, Sn, Pb are amphoteric in nature.

Examples of amphoteric oxides are ZnO, SnO2, etc.

 ZnO + 2HCl -------------> ZnCl2 + H2O
ZnO + 2NaOH -------------> Na2ZnO2 + H2O
  • Peroxides :

These are the oxides which contain O2-2 ion and combines with acides to form hydrogen peroxides.

Examples of peroxides are  Na2O2, BaO 2, ZnO2 etc.

BaO2 + H2SO4 -------------> BaSO4 + H2O2
  • Mixed oxides :

These are the oxides which are formed by the combination of two or more simple oxides they react with acids to give two different salts.

Examples of mixed oxides are Fe3 O4 ( FeO + Fe2O3), Pb3O4 ( 2PbO + PbO2 ), Mn3O4 (2MnO + MnO 2) etc.

Fe3O4 + 8HCL -------------> 2FeCl3 + FeCl2 + 4H2O

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