Is water a base?

Water is neither a strong acid nor a strong base; it is a neutral substance that can act as both, making it amphoteric.

Water has a neutral pH 7 because it can both donate and accept protons (H⁺). In one molecule, H₂O can act as an acid by donating H⁺ to form OH⁻, or as a base by accepting H⁺ to form H₃O⁺. This self-ionization property is shown by H₂O ⇌ H⁺ + OH⁻.

Thus, water behaves as a base in presence of strong acids and as an acid in presence of strong bases. This dual nature makes it amphoteric, essential in acid-base balance and many reactions. Example: with HCl, water acts as base; with NH₃, water acts as acid.