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Question: Water is a _______ ?...

Water is a _______ ?

Explanation

Solution

Water is always used to dilute acids and bases. If water could itself react with an acid or a base (neutralization reaction) then it would not have been a suitable diluting agent. Moreover solutions of acids and bases can be prepared in water indicating its inertness towards an acid-base reaction.

Complete answer:
Any molecule can be classified as an acid or a base depending upon its reactions with other acids or bases.
According to the Arrhenius Acid-base theory, any chemical compound that releases hydrogen ions (or protons) in aqueous solutions is called an acid and the one that releases hydroxide ions in aqueous solution is called a base.
The strength of an Arrhenius acid is determined by the amount of hydrogen ions H+{H^ + } released and that of an Arrhenius base is determined by the amount of hydroxide ions OH−O{H^ - } released by it. The higher the amount of H+{H^ + } ions released, lower will the pH and stronger will be the acid. The higher the amount of OH−O{H^ - } ions released, higher will be the pH and stronger will be the base.
But water is a neutral molecule on the pH scale. In fact, different acids and bases are compared on the pH scale relative to water which has a pH of 7.
Water on dissociations gives both H+{H^ + } as well as OH−O{H^ - } ions.
H2O⇌H++OH−{H_2}O \rightleftharpoons {H^ + } + O{H^ - }
Thus water is a neutral compound according to Arrhenius theory.
But according to the Bronsted-Lowry acid base theory, water can accept as well as donate H+{H^ + } ions. It behaves like an acid in presence of a stronger base (gets deprotonated) and a base in the presence of a stronger acid (gets protonated).
Thus water is a neutral molecule according to Arrhenius theory and an amphoteric compound according to the Bronsted-Lowry acid base theory.

Note:
Being neutral is not the same as being amphoteric. Water is neutral because it releases both H+{H^ + } as well as OH−O{H^ - } ions in equal amounts but it is amphoteric according to the Bronsted-Lowry acid base theory as it reacts with both acids and bases.