Explain the concept of Bronsted acids and Bronsted bases. Illustrate the answer with suitable examples.

Explanation

According to Bronsted theory a substance which can donate a proton to the other substance is known as acid. A substance which accept a proton from other substance is a base.
`Ex: HCl +H_(2)O hArr H_(3)O^(+)+Cl^(-)`
`NH_(3)+H_(2)O NH_(4)^(+) +OH^(-)`
Here HCI donates a proton to water and behaves as Bronsted Lowry acid. Similarly `NH_(3)` accepts a proton from `H_(2)O` and acts as Bronisted Lowry base.
Above reaction is a reversible reaction so that `H_(3)O^(+)` can donate proton to act as acid. `Cl^(-)` can accept a proton to act as base. Thus each acid base reaction equilibrium involves two acids and two bases. Each pair differs by a proton, such acid base pair is called Conjugate acid base patr.
Ex `: underset("acid")HCl overset(-H^(+)) underset(+H^(+)) hArr underset("base")(Cl^(-))`
`: underset("acid")H_(3)O^(+) overset(-H^(+)) underset(+H^(+)) hArr underset("base")(H_(2)O)`
According to this theory strengths of acids and bases can be explained.
An acid which show great tendency to donate protons is a strong acid and an acid which shows less tendency to donate proton is a weak acid,
Abase which shows great tendency to accept a proton is a strong base and a base which shows less tendency to accept a profon is a weak base.