1. Bases have a bitter taste and are slippery to touch.
2. Strong bases such as caustic soda (NaOH) and caustic potash are corrosive in nature and can harm the skin. These bases are highly soluble in water and the dissolution process is exothermic.
3. Alkalies are good conductors of electricity.
4. Indicator Properties
Aqueous solutions of bases impart specific colours to the acid-base indicators.
- They tum red litmus blue.
- They impart pink colour to phenolphthalein.
- They impart yellow colour to methyl orange.
- They impart yellow colour to methyl red.
5. Reaction with Acids
Bases react with acids to form salt and water
Base + Acid àSalt + Water
KOH + HCl àKCl + H2O
2NaOH + H2O àNa2SO4 + H2O
The reaction is known as neutralization.
6. Reaction with Metals
Certain metals such as zinc, aluminium, tin and lead react with strong alkali solutions, on heating, and hydrogen gas is evolved.
7. Reaction with Non-metallic Oxides
Non-metallic oxides are generally acidic in nature. They react with bases to form salt and water.
Base + Non-metallic àoxide Salt + Water
Ca(OH)2 + CO2 à CaCO3 + H2O
2KOH + CO2 à K2CO3 + H2O
2NaOH + SO2 àNaSO3 + H2O
Concentrated solution of caustic potash is used for absorbing carbon(IV) oxide gas.
8. Reaction with Metallic Oxides
Certain metal oxides can act as bases as well as acids.These are known as amphoteric oxides. For example, zinc oxide (ZnO), lead(II) oxide.(PbO), aluminium oxide (.Al2O3).
These oxides on reaction with hot alkali solutions form complex salts and dissolve.
In these reactions metal oxides are acting as acids.
Now, let us learn about the various concepts of acids and bases: