7.5 Oxides
Binary compounds of elements with oxygen are called oxides. For example, CaO, CO2 SO2 Na2O CuO Al2O3 etc.
Oxides can be classified as acidic, basic, or amphoteric based on their chemical properties and their relationship with metallic and non- metallic elements.
1.Acidic Oxides
Acidic oxides typically form acids when they react with water. They are oxides of non- metals. Examples include:
SO2 (Sulphur dioxide): Reacts with water to form sulphurous acid H2SO3
CO2(Carbon Dioxide):Reacts with water to form carbonic acid (H2CO3).
2.Basic Oxides
Basic oxides form bases when they react with water. They are oxides of metals. Examples include:
Na2O (sodium oxide): Reacts with acids to form salts and water, indicating its basic nature.
CaO (Calcium Oxide): Reacts with water to form calcium hydroxide Ca(OH)2 ),a strong base. It reacts with acids to form salt.
3.Amphoteric Oxides
Ampoteric oxides can react both with acids and bases, displaying both acidic and basic properties. These are oxides of some metals. Examples include:
Al2O3 (Aluminum Oxide): Reacts with acids to form salts and water, and with bases to form aluminates.
With acid (HCl):
With base (NaOH):
Sodium aluminate
ZnO (Zinc Oxide): Reacts with acids to form salts and water, and with bases to form zincates. With acid (HCl):
With base (NaOH):
Sodium zincate
7.5 General characteristics of metals
Metals exhibit various chemical properties based on their reactions with different substances, including dilute acids, cold water, steam, and oxygen.
Reactions with Dilute Acids
Metals react with dilute acids to form a salt and hydrogen gas.