Ncert Exercises & Solutions

Boric acid is an acid because its molecule

1. Contains replaceable H⁺ ion

2. Gives up a proton

3. Accepts OH^- from water releasing proton

4. Combines with proton from water molecule

Hint: Boric acid, that is, H₃BO₃ is a lewis acid.

Lewis acids are substances whose octet is incomplete and accepts electrons.

Boric acid is a monobasic weak acid. It does not liberate H⁺ ion but accepts electrons from OH^- ion i.e., behaves as Lewis acid.

H_{3} {BO}_{3} + H_{2} O \to B {(OH)}_{4}^{-} + H^{+}

or,

B {(OH)}_{3} + 2 H_{2} O \to {[B {(OH)}_{4}]}^{-} + H_{3} O^{+}

The structure of H₃BO₃ is as shown below, where the octet of boron in H₃BO₃ is incomplete.