Page 139 - ICSE Chemistry 8

CLASSIFICATION OF OXIDES

Oxides are of four types depending upon the nature and proper es of the compounds.

1. Acidic oxides
2. Basic oxides

3. Neutral oxides
4. Amphoteric oxides

Acidic Oxides

Acidic oxides or non-metallic oxides are formed when non-metals are heated in the presence of oxygen.

• Non-metals react with oxygen to produce acidic oxides.
Non-metals like carbon, sulphur, nitrogen and hydrogen combine with oxygen to produce their
oxides.

C(s) + O (g) Heat CO (g)
2
2
Carbon Oxygen Carbon dioxide
S(s) + O (g) Heat SO (g)
2
2
Sulphur Oxygen Sulphur dioxide
N (s) + O (g) High temperature 2NO(g)
2
2
Nitrogen Oxygen Nitric oxide
• Most of the acidic oxides turn moist blue litmus paper red.

• Acidic oxides are usually gases at room temperature.
• Acidic oxides dissolve in water to produce acids.

CO (g) + H O(l) H CO (aq)
2
2
2
3
Carbon dioxide Water Carbonic acid
SO (g) + H O(l) H SO (aq)
3
2
2
2
Sulphur dioxide Water Sulphurous acid
SO (g) + H O(l) H SO (aq)
4
2
3
2
Sulphur trioxide Water Sulphuric acid
2NO (g) + H O(l) HNO (aq) + HNO (aq)
2
2
3
2
Nitrogen dioxide Water Nitrous acid Nitric acid
• Acidic oxides react with base and alkali to form salt and water.
CO (g) + 2NaOH(aq) Na CO (aq) + H O(l)
3
2
2
2
Carbon dioxide Sodium hydroxide Sodium carbonate Water
SO (g) + KOH(aq) K SO (aq) + H O(l)
2
2
3
2
Sulphur dioxide Potassium hydroxide Potassium sulphite Water
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