question_answer 39)

  Calcium phosphate is present in tooth enamel. Its nature is                 (a) basic                               (b) acidic                              (c) neutral                           (d) amphoteric                

Answer:

  (a) Calcium phosphateis basic salt, as it is a salt of weak acid (phosphoric acid) and slightly stronger base (calcium hydroxide) (though both are weak). Also when pH of our mouth falls below 5.5 due to eating of sweets etc., i.e., mouth is acidic, the dissolution of enamel (calcium phosphate) starts which shows that calcium phosphate is basic in nature.