Question

Aqueous solution of borax is:
(A) neutral
(B) amphoteric
(C) basic
(D) acidic

Answer 1

Hint: Boric acid and hydroxyl ion is yielded by the aqueous solution of borax. This hydroxyl ion will react with sodium to form sodium hydroxide (NaOH) which has a strong basic nature. A strong base and a weak acid will try to neutralize each other but because of the high basic strength exerted by NaOH the solution becomes alkaline.

Complete step by step answer:
- Borax is a compound of boron which is having the molecular formula $N{{a}_{2}}{{B}_{4}}{{O}_{7}}.10{{H}_{2}}O$. It’s a salt of a mild boric acid and a sodium base. Disodium tetraborate, sodium borate are other names of borax.
 - The aqueous solution of borax undergoes the following reaction :
 \[N{{a}_{2}}{{B}_{4}}{{O}_{7}}.10{{H}_{2}}O+7{{H}_{2}}O\to 2NaOH+4{{H}_{3}}B{{O}_{3}}+10{{H}_{2}}O\]

The borax gets hydrolyzed in the aqueous solution and the borate ion donate the hydroxyl (OH) group in the solution, This hydroxyl ion will then reacts with sodium to form sodium hydroxide (NaOH) in the solution and as we know sodium hydroxide is a very strong base.
- The borax is also dissociated into ${{H}_{3}}B{{O}_{3}}$ (Boric acid) which is a weak acid in nature. As a result, the strongly basic sodium hydroxide and weakly acidic boric acid, will try to neutralize each other. But because of the high basic strength of NaOH, the boric acid cannot completely neutralize it in the solution and as a result the aqueous solution of borax will be slightly basic in nature.
So, the correct answer is “Option C”.

Note: Keep in mind that the borax is an essential part of numerous cosmetics, detergents and glazing and is used for buffer solutions in biochemistry , as an anti-fungal material , as a fire resistance , as a metallurgy fluid and as precursor to other boron compounds.