PROPERTIES OF ACIDS

properties and classification of acids 

We can categorize a substance as an acid or a base according to the properties. Let us learn the characteristics properties of acids.

Properties of acids

The following are the characteristic properties of acids:

1.Taste :

 The sour taste of many unripe fruits , lemon , vinegar and sour milk is caused by the acids present in them. Hence , we can say that acids have a sour taste.                                      

                                     Acids present in some substances .

2. Action on indicators. 

Indicators show different colours in presence of acid and bases . The three commonly used indicator in presence of acids. 

                                colour of some indicator in presence of acids . 

3. Conduction of electricity and dissociation of acids 

When acids are dissolve in water they produce ions which help in conducting the electricity. This process is known as dissociation . More specifically , acids produce hydrogen ions (H+) which are responsible for all their characteristic properties . These ions do not exit as H+ in the solution but combine with water molecules as shown below:

On the basis of the extent of dissociation occurring in their aqueous solution , acids are classified as strong and weak acids.

properties of acid:

1. Acids are sour in taste.

 2. Acid molecules contain hydrogen ion (H+ ) as a main costituent. 

3. Acid reacts with metal to form hydrogen gas.

 4. Acid reacts with carbonates and liberates CO2 gas. 

5. Blue litmus turns red in acid.

uses of acids 

1. Acids are used in the production of chemical fertilizers. 

2. Acids are used in the production of explosives, oil purification, medicines, dyes and paints. 3. Hydrochloric acid is used for the preparation of different types of chloride salts. 

4. Dil. H2 SO4 acid is used in the batteries. (electric cell)

 5. Dil. HCl is used for sterilization of water.

 6. Acid is used for making of white paper from wood pulp.

CLASSIFICATION OF ACIDS 

(I) On the basis of their source acids are of two type:-

(i) Mineral acids 

(ii) Organic acids

(i) Mineral Acids (Inorganic acids) :-

The acids which are usually obtained from minerals are known as inorganic acids.

  

Name	chemical formula	where found or used
Hydrochloric acid	HCl	In purification  of common salt, in textile industry as bleaching agent, to make aqua regia
Sulphuric acid	H2SO4	Commonly used in car batteries, in the manufacture of fertilizers (Ammonium phosphate, Super phosphate detergents etc, in paints, plastics, drugs)
Nitric acid	HNO3	manufacture of artificial silk, in petroleum refining. Used in the manufacture of explosives (TNT, Nitroglycerine) and fertilizers (Ammonium nitrate, Calcium nitrate, Purification of Au, Ag.
Carbonic acid	H2CO3	In soft drinks and lends fizz, In stomach as gastric juice, used in tanning industry.
Phosphoric acid	H3PO4	Used in antirust paints and in fertilizers

 (ii) Organic Acids :-

The acids which are usually obtained from plants and animals are known as organic acids.

Name	Where found or used
Citric acid	Present in lemon, orange and citrus fruits
Lactic acid	Responsible for souring of milk in curd
Benzoic acid	Used as a food preservative
Formic acid (HCOOH)	Found in the stings of ants and bees, used in tanning leather, in medicines for treating gout.
Tartaric acid	Present in tamarind.
Acetic acid (CH3COOH)	Found in vinegar, used as solvent in the manufacture of dyes and perfumes

 (II) Classification on the basis of their strength :-

(i) Strong Acid :-

The acid which undergoes complete ionisation in aqueous solution are known as strong acids.

(ii) Weak Acid :-

The acid which undergoes partial or incomplete ionisation in aqueous solution are known as weak acids.

(III) Classification on the basis of concentration of the Acid :-

Dilute Acid :- 

The acids which contains more amount of water is called a dilute acid. 

 "Strength of an acid is not depend upon the concentration of an acid"

Concentrated Acid :- 

The acids which contains very small amount of water is called a concentrated acid.