(a) A common acid base indicator and a universal indicator: Acid base indicator like litmus tells us only whether a given substance is an acid or a base. Universal indicator gives an idea as to how acidic or basic a substance is. An universal indicator gives different colours with solutions of different p H values.
(b) Acidity of bases and basicity of acids Acidity of bases: The number of hydroxyl ions which can be produced per molecule of the base in aqueous solution.
Basicity of acid: The basicity of an acid is defined as the number of hydronium ions that can be produced by the ionization of one molecule of that acid in aqueous solution.
(c) Acid and alkali: An acid is that substance which gives H+ ions when dissolved in water An alkali is that substance which gives OH- ions when dissolved in water.
