1. Lone Pair of Electrons: Ammonia has a lone pair of electrons on the nitrogen atom. This lone pair is readily available to accept a proton, making ammonia a Lewis base.
2. Formation of Ammonium Ion: When ammonia reacts with an acid, the lone pair on the nitrogen atom accepts a proton from the acid, forming the ammonium ion (NH4+). This reaction is an equilibrium reaction:
NH3 + H+ ⇌ NH4+
3. Brønsted-Lowry Definition: According to the Brønsted-Lowry definition of acids and bases, a base is a substance that accepts a proton. Ammonia fits this definition because it readily accepts a proton from an acid, forming the ammonium ion.
Example:
When ammonia reacts with hydrochloric acid (HCl), the following reaction occurs:
NH3 + HCl ⇌ NH4+ + Cl-
In this reaction, ammonia accepts a proton from HCl, forming the ammonium ion (NH4+) and chloride ion (Cl-). This reaction is a classic example of ammonia acting as a base.
Conclusion:
Ammonia's ability to accept a proton due to its lone pair of electrons makes it a base according to both the Lewis and Brønsted-Lowry definitions. Its reaction with acids results in the formation of the ammonium ion, a classic characteristic of a base reacting with an acid.
