*Acids:-Those compounds which are
gives H+ ion in the water solution,
are called acids.These are sour
taste , turn blue litmus paper to red
an pH lower then 7.
(a) HCl ⇌ H+ + Cl-
(b) H2So4 ⇌ H+ + HSo4-
*Bases:-Those compounds which are gives OH- ion in the water solution called base. These are bitter in taste
and,turn red litmus paper to blue ,
and pH higher than 7. Examples: (a) NaOH ⇌ Na+ + OH-
(b) Ca(OH)2 ⇌ Ca2+ + 2 OH-
This theory was related because it
Could not respected the acidic and
basic character are substance.
(2). Bronsted Or Lowery theory/ concept(1923):- 'Bronsted' theory purpose the new theory in - 1923 and 'Lowery' also
give same theory independently :
* Acid:According to this concept an
acid is a substance that can 'donate' the proton (H+ ion proton donor).
These proton are not in the 'freedom'
state in the water solution.These are
react with water molecule and produce
the hydronium ion(H3O ion).
(a) H+ + H2O ⇌ H3O+
(b) HCl ⇌ H+ + Cl-
*Base: According to Bronsted or Lowery theory : Base is a substance that can 'accept the proton' are called base and these base are called 'proton acceptor'
NH3 + H3O ⇌ NH4+ + H2O
(3). Lewis's Theory/concept(1939):-
According to Lewis's theory :
*Acid: Those acids which can 'accept a pair of electron' and 'make a Co- ordinate bond' , called acids.Thesre acids are electron pair acceptor.
*Base:Those base which can 'donate a pair of electron' to form a Co-ordinate
bond , called lewis base.These base are 'electron pair donor'.