How do classify the behaviour of water as an acid?

1 Answer
May 25, 2017

Answer:

Water is an #"amphoteric species"# according to the #"Bronsted Lowry concept."#

Explanation:

According to the #"Lewis concept"#, water is also amphoteric.

A Lewis acid is defined as an electron-pair acceptor; and a Lewis base in an electron pair donor. Water's dual classification can be appreciated from the autoprotolysis reaction of water:

#2H_2O(l) rightleftharpoonsH_3O^(+)+HO^(-)#

While this (carefully measured!) equilibrium lies strongly to the left, water has clearly acted as a Lewis base to give the #"hydronium ion"#, and as a Lewis acid to give the #"hydroxide ion"#.