Question

Boric acid is an acid because its molecule

• A. Contains replaceable $H^{+}$ ion
  
• B. Gives up a proton
• C. Combines with proton from water molecules
• D. Accepts $O{H}^{-}$ from water releasing proton
  

Answer 1

The correct option is D Accepts $O{H}^{-}$ from water releasing proton


Boric acid is a weak monobasic acid.
It is not a protonic acid or Arrhenius acid that produces one $H^{+}$ ion in water.

Instead, it acts as a lewis acid by accepting electrons from hydroxyl ion$\left(O{H}^{-}\right)$ of water as boron has one empty 2p orbital to accept electrons.

$B(OH{)}_3+2H_{2}O\to [B(OH{)}_4{]}^{-}+H_3{O}^{+}$

Boric acid has 3 OH groups, but none of them ionizes in water to produce $H^{+}$ ion. Hence, it is not protonic acid.