Boric acid is an acid because its molecule:
[amp_mcq option1=”accepts OH– from water” option2=”combines with proton from water molecule” option3=”contains replaceable H+ ion” option4=”gives up a proton” correct=”option1″]
This question was previously asked in
UPSC NDA-2 – 2015
Boric acid (H₃BO₃) is a weak monoprotic Lewis acid. It does not directly donate a proton (H⁺) from its own molecule in aqueous solution. Instead, it accepts a hydroxide ion (OH⁻) from a water molecule, releasing a proton from the water molecule in the process. The reaction is: H₃BO₃ + H₂O ⇌ [B(OH)₄]⁻ + H⁺. Therefore, it acts as an acid by accepting an OH⁻ ion from water.
Boric acid’s acidity is explained by its behavior as a Lewis acid, accepting an electron pair from the hydroxide ion of water.