A wide variety of materials consists essentially of elements and compounds having different characteristics
    exist around us. Some of them are sour, some are bitter, while some are salty in taste.
    For Example – Sour and bitter tastes of food are due to acids and bases, respectively, present in them.
    Acids react with bases to produce salt whose properties are different from acid and base.


    The term "acid" is derived from the latin word "acidus" meaning sour to taste.
    Example – Sour taste of lemon, unripened grapes, Vinegar, tomatoes etc.

*    According to Arrhenius theory :
    "An acid is a substance which dissolved in water, it ionizes and releases hydrogen ions [H+(aq.)] in solution".
    Note :- Hydrogen ion do not exist as H+ ions in solution, they attach themselves to the polar 
    water molecules to form hydronium ions or hydroxonium ions, (H3OÅ or H+(aq.))

Classification of acids

(I)    On the basis of their source acids are of two type –
    (i) Mineral acids         (ii) Organic acids
    (i) Mineral Acids (Inorganic acids) :-
    The acids which are usually obtained from minerals are known as inorganic acids.

    (ii) Organic Acids :-
    The acids which are usually obtained from plants and animals are known as organic acids.

(II)    On the Basis of their Basicity :-
    "The  basicity of an acid is the number of replaceable hydrogen atoms present in a molecule that can
    be produced by the complete ionisation of one molecule of that acid in aqueous solution."
    "Basicity of an acid is determined by number of hydronium ions (H3O+/H+(aq)) produced per molecule of an acid on ionisation."
    (i) Monobasic Acids :-

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