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Properties of bases

Bases

Substances with bitter taste and give a soapy touch are known as bases but many bases have corrosive nature. So bases are defined as " 

According to Arrhenius :

those substances which give hydroxide or hydroxyl ion (OH-)in their aqueous solution" are called bases.

Properties of Bases

The following are the characteristic properties of bases:

 1. Taste and Touch 

Bases have a bitter taste and their solutions are soapy to touch.

2. Action on indicators.

The colours shown by three commonly used indicators in presence of bases are listed below for easy recall. 

  colours of some common indicators in basic solution

 Indicator 

colour in basic medium  

 1. Litmus 

Blue  

 2. Phenolphthalein 

Pink  

 3. Methyl orange 

Yellow  

3.Conduction of electricity and dissociation of bases 

Aqueous solutions (solution in water ) of basesconduct electricity which is due to the formation of ions. Like acids, bases also dissociate on dissolving in water. Bases produce hydroxyl ions (OH-)  which are responsible for their characteristic properties.

The bases which are soluble in water and give OH- ions in their aqueous solution are called alkalies. All alkalies are bases but all bases are not alkalies.

Uses of bases 

 S.NO

Base  

Use  

 1.

 Ammonium hydroxide (NH4OH) 

 It is used in removing grease stains from clothes.

 2.

 Sodium hydroxide (NaOH)

 It is used in the manufacture of washing soap, paper, petrol refining and as a reagent in the laboratory.

 3.

  Sodium carbonate (Na2CO3)

 It is used as a cleaning agent for domestic purposes and also for removing permanent hardness of water.

 4.

 Potassium hydroxide (KOH)

 It is used in the manufacture of soap paper (bathing soap) and alkaline batteries.

 5.

Magnesium hydroxide [Mg(OH)2] 

 It is used as an antacid

 6.

 Aluminium hydroxide [Al(OH)3]

 It is used as a foaming agent in fire extinguishers.

 7.

Calcium hydroxide (Slaked lime) [Ca(OH)2]

 It is used in the manufacture of bleaching powder and softening of hard water.

 








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