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.

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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.