An acid is a substance that donates a hydrogen ion (H+) in a chemical reaction, while an alkali is a substance that donates a hydroxide ion (OH-) in a chemical reaction. Water can be both acidic and basic depending on the chemical reactions it is involved in.
For example, when water reacts with an acid, it acts as a base and accepts hydrogen ions, forming hydronium ions (H3O+).
On the other hand, when water reacts with a base, it acts as an acid and donates hydrogen ions, forming hydroxide ions.
