Bronsted Theory:
Bronsted/Lowry acid: Substance that donates proton [H+].
Example: HCl, CH3COOH, H2CO3
Bronsted/Lowry base: Substance that accepts proton [H+].
Example: NH3, HCO3-, SO42-
Limitation:
1. Theory is based on proton transfer but there are many other compounds which do not donates proton and acts as acid. There are many acid-base reactions where proton transfer is not involved.
SO2 + SO2 → SO2+ +SO32-
All Arrhenius acids and bases are Bronsted/Lowry acid and bases.
Water is having dual character as it accepts and donates proton. Such types of compounds are called as amphoteric compounds.
H2O + HCl → H3O+ +Cl-……………………(1)
H2O + NH3 → NH3+ +OH-……………………(2)
In first reaction water accepts proton from HCl and act as a base whereas in second reaction it donates proton to ammonia and act as an acid.
When an acid transfers its proton it becomes the conjugate base (CB) and once a base accepts the proton it becomes the conjugate acid (CA). So, in first reaction Cl- is conjugate base and H3O+ is conjugate acid.
Lewis Theory:
Lewis acid: Substance that accepts electron pair
Example: H+, NH4+, Na+
Lewis base: Substance that donates electron pair
Example: NH3, OH-, Cl-, CN-
Limitation:
1. Theory is based on transfer of electron pair so reactions are expected to be very fast however there are many other acid-base reactions which are very slow.
All Bronsted/Lowry acids and bases are Lewis acids and bases.