Question

On the addition of mineral acid to an aqueous solution of borax, the following compound is formed :

• A. boron hydride.
• B. ortho-boric acid.
• C. meta-boric acid.
• D. pyro-boric acid.

Answer 1

The correct option is B ortho-boric acid.

Ortho boric acid ($4B\left(OH{)}_3\right[or{H}_{3}B{O}_3]$) may be prepared by reacting borax (sodium tetraborate decahydrate $N{a}_2{B}_4{O}_7.10H_{2}O$) with a mineral acid , such as hydrochloric acid

$N{a}_2{B}_4{O}_7.10H_{2}O+2HCl\to 4B\left(OH{)}_3\right[or{H}_{3}B{O}_3]+2NaCl+5H_{2}O$

Hence option B is correct.