Acidic Behavior of Orthoboric Acid in Water
STATEMENT-1 : In water, orthoboric acid behaves as a weak monobasic acid.
because
STATEMENT-2 : In water, orthoboric acid acts as a proton donor.
Options
Statement-1 is True, Statement-2 is True; Statement-2 is a correct explanation for Statement-1
Statement-1 is True, Statement-2 is True; Statement-2 is NOT a correct explanation for Statement-1
Statement-1 is True, Statement-2 is False
Statement-1 is False, Statement-2 is True
Topics & Concepts
Step-by-Step Solution
To determine the correct option, let us analyze both statements:
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Analysis of STATEMENT-1:
Orthoboric acid, represented as or , has a central boron atom surrounded by six valence electrons, which leaves its octet incomplete. In an aqueous solution, it acts as a Lewis acid by accepting a lone pair of electrons from the oxygen atom of a hydroxide ion () derived from a water molecule:
Because each mole of results in the liberation of one mole of hydronium ions (), and the equilibrium constant is small (), it behaves as a weak monobasic acid.
Therefore, STATEMENT-1 is True. -
Analysis of STATEMENT-2:
A Brønsted-Lowry acid acts directly as a proton donor by ionizing to release from its own molecular structure. Orthoboric acid does not donate its own protons; instead, it behaves as a Lewis acid by accepting an ion from water, causing the water molecule to release a proton ().
Therefore, orthoboric acid acts as a Lewis acid (electron-pair acceptor) rather than a proton donor.
Therefore, STATEMENT-2 is False.
Since Statement-1 is True and Statement-2 is False, the correct choice is (C).