Acid and Bases
(1) Arrhenius concept: According to Arrhenius concept all substances which give H+ ions when dissolved in water are called acids while those which ionise in water to furnish OH– ions are called bases.
Some acids and bases ionise almost completely in solutions and are called strong acids and bases. Others are dissociated to a limited extent in solutions and are termed weak acids and bases. , etc., are examples of strong acids and are strong bases. Every hydrogen compound cannot be regarded as an acid, e.g., is not an acid. Similarly, , etc., have groups but they are not bases.