Question

Write chemical reactions to show the amphoteric nature of water.

Answer 1

The amphoteric nature of water can be described on the basis of the following reactions:

1. Reaction with H₂S-
   The reaction takes place as:
   \[\ce{\underset{Base}{H2O_{(l)}} + \underset{Acid}{H2S_{(aq)}} <=> \underset{Conjugate acid}{H3O^+_{(aq)}} + \underset{Conjugate base}{HS^-_{(aq)}}}\]
   In the forward reaction, \[\ce{H_2O_{(l)}}\] accepts a proton from \[\ce{H_2S_{(aq)}}\]. Hence, it acts as a Lewis base.
2. Reaction with NH₃-
   The reaction takes place as:
   
   In the forward reaction, `H_2O` denotes its proton to`NH_(3(aq))`. Hence, it acts as a Lewis acid.
3. Self-ionization of water-
   In the reaction, two water molecules react as: