Question

n-factor of ${{H}_{3}}B{{O}_{3}}$ in aqueous solution will be:
A. 1
B. 2
C. 3
D. 4

Answer 1

${{H}_{3}}B{{O}_{3}}$ is also called boric acid. Acids have a property of liberating ${{H}^{+}}$ ions very easily when dissolved in a polar solvent. For acids, the n-factor is nothing but the number of replaceable ${{H}^{+}}$ ions by the reaction of one mole of an acid.

Complete step by step answer:
- Before going to know about the n-factor for boric acid we should know the structure of it.
- The structure of the boric acid is as follows.

- Boric acid contains three hydrogens which are attached to three oxygen atoms.
- Even though boric acid contains three ${{H}^{+}}$ ions the n-factor is not 3.
- Because the three hydrogens attached to boron through oxygen are not replaceable.
- Boron atom in boric acid acts as a Lewis acid (means electron deficient), then the lone pair of electrons present in the oxygen of water attack on boron in boric acid.
- The chemical reaction of boric acid with water is as follows.
${{H}_{3}}B{{O}_{3}}+2{{H}_{2}}O\to {{[B{{(OH)}_{4}}]}^{-}}+{{H}_{3}}{{O}^{+}}$
- From the above reaction we can say easily that the n-factor for boric acid is 1.

- So, the correct option is A.

Note: n-factor for an acid or a base is not equal to the number of ${{H}^{+}}$ ions or $O{{H}^{-}}$ ions present. n-factor for acids is nothing but the number of ${{H}^{+}}$ ions are going to replaceable when an acid is going to reacts with water and for base n-factor will be the number of $O{{H}^{-}}$ ions are going to replaceable when a base is going to reacts with water.