Arrhenius Concept of Acids and Bases - Home of Knowledge

Arrhenius Concept of Acids and Bases

Arrhenius Concept of Acids and Bases

According to Arrhenius concept (1787):

Acid is a substance which dissociates in aqueous solution to give hydrogen ions.

 

For example, substances such as HCl, HNO3 , CH3 COOH, HCN, etc., are acids because they ionize in aqueous solutions to provide H+ ions.

  H2SO4 + H2O H3O+ + HSO4

HCl  —water→  H+  +  Cl

On the other hand, base is a substance which dissociates in aqueous solution to give hydroxide ions.

 

The substances such as NaOH, KOH, NH4 OH, Ca(OH)2 etc. are bases because these compounds ionize in aqueous solutions to provide OH ions.

 

NaOH > Na+ + OH‾

Ca(OH)2 ==> CaO + H2O

Thus, according to Arrhenius Concept:

Acids give H+ ions in water, bases give OH ions in water.

 

Examples of some important acids and bases are given in Table.

Table : Acids and Bases :

Acids Bases

Hydrochioric acid, HCI

Nitric acid, HNO3

Sulphuric acid, H2SO4

Phosphoric acid, H3PO4

Sodium hydroxide, NaOH

Potassium hydroxide, KOH

Calcium hydroxide, Ca(OH)2

Aluminium hydroxide, Al(OH)3

 

 

Limitation of Arrhenius concept:

  1. This concept is applicable only in aqueous medium and does not explain nature of acids and bases in non-aqueous medium.
  2. According to this concept, acids and bases are only those compounds which contain hydrogen (H+) and hydroxyl or hydroxide (OH) ions, respectively. It can’t explain the nature of compounds like CO2, NH3, etc. which are acid and base, respectively.

Although this concept has limited scope yet, it led to the development of more general theories of acid-base behavior.

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