What do you understand by the term 'auto-protolysis' of water? What is its significance?

Explanation

Self ionisation of water is called auto-protolysis. Self ionisation of water can be expressed by the given equation-
`underset("Acid-1")(H_(2)O(l)) + underset("Base-2")(H_(2)O(l)) hArr H_(3)O^(+) (aq) + underset("Base-1")(OH^(-1))(aq)`
Water exhibits amphoteric property because of autoprotolysis. Thus water reacts with both acids and bases. It usually acts as a base in the presence of an acid stronger than it and acts as an base in the presence of a base stronger than it. for Example,
`underset("Acid-1")(H_(2)O(l)) + underset("Base-2")(NH_(3))(aq) rarr underset(Acid-2)(NH_(4)^(+))(aq) + underset("Base-1")(OH^(-1))(aq)`
`underset("Base-1")(H_(2)O(l)) + underset("Acid-2")("HCl")(aq) rarr underset(Acid-1)(H_(3)O^(+))(aq) + underset("Base-2")(Cl^(-1))(aq)`