Question

Liquid $N{H_3}$ , like water is an amphoteric solvent. Write the equation for the auto-ionisation of the $N{H_3}$ ?

Answer 1

Hint : Amphoteric word is derived from the Greek letter ‘amphi’ which means both. So basically amphoteric substances or molecules or ions are those chemical species that can act as both the acids and bases. And water is one of the best examples of the amphoteric nature.

Complete Step By Step Answer:
In the question, it is stated that the liquid is an amphoteric solvent, so it will obviously undergo auto-ionisation reaction well.
Hence, it is clear from the above that amphoteric substances, molecules or ions can act as both the acids and bases.
So, ammonia $N{H_3}$ , will also act as Bronsted-Lowry acid and base both.
Before moving further let’s first understand the concept of Bronsted-Lowry acid and base:
So, according to the Bronsted-Lowry acid and base concept, the Bronsted-lowry acid is the chemical species which donated the ${H^ + }$ ions. And the Bronsted-Lowry base is the chemical species that accepts the ${H^ + }$ ions.
So, now we will see the auto-ionisation of ammonia.
Hence, the reaction is:
$2N{H_3}\underset {} \leftrightarrows NH_4^ + + NH_2^ -$
Here, in this reaction $NH_4^ +$ is a conjugate acid and $NH_2^ -$ is a conjugate base.
So, this is our answer and justification for the amphoteric nature of the ammonia solvent and the auto-ionisation of ammonia, $N{H_3}$ .

Note :
Here, two molecules of ammonia reacted with each other, one of the molecules of the ammonia acted as a base and accepted the ${H^ + }$ ions and formed the conjugate acid as $NH_4^ +$ . While on the other hand the other molecule of ammonia acted as an acid and donated its ${H^ + }$ ions and produced a conjugate base as $NH_2^ -$ . Thus ammonia is an amphoteric solvent.