11th Class Chemistry The p-Block Elements-I

  • question_answer 52)   Boric acid is an acid because the molecule : (a) contains replaceable hydrogen ion                    (b) gives up a proton (c) accepts\[O{{H}^{-}}\] from water releasing proton    (d) combines with proton from water molecule

    Answer:

      (c) \[{{H}_{3}}B{{O}_{3}}\]or\[{{H}_{3}}B{{O}_{3}}\] in aqueous solution coordinates with a water molecule to form a hydrated species.   \[{{B}^{3+}}\]ion pulls the \[\sigma \]-electron charge of the coordinated O-atom towards itself. The coordinated oxygen, in turn, pulls the \[\sigma \]-electron charge of the O-H bond of the attached water molecule. This facilitates the removal of \[{{H}^{+}}\] ion from the O-H bond. Thus, the aqueous  solution of\[{{H}_{3}}B{{O}_{3}}\] acts as a weak acid.     or\[B{{(OH)}_{3}}\] accepts \[O{{H}^{-}}\] from water and releases \[{{H}^{+}}\] and it acts as a weak acid.


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