Question

Which of the following is/are method(s) to prepare borax?

• A. Dissolving tincal in boiling water
• B. Heating colemanite along with soda ash
• C. Treating colemanite with sulphuric acid
• D. Neutralising boric acid with soda ash

Answer 1

Answer: (A), (B), (D)

The correct options are
A Dissolving tincal in boiling water
B Heating colemanite along with soda ash
D Neutralising boric acid with soda ash

Dissolving tincal in boiling water and removing impurities will form an aqueous solution of borax. After concentrating this solution followed by cooling, crystals of borax are formed.

Colemanite on heating along with fly ash gives borax. The reaction is as below:
$C{a}_2{B}_6{O}_{11}\left(s\right)+2N{a}_{2}C{O}_3\left(s\right)\to 2CaC{O}_3\left(s\right)+N{a}_2{B}_4{O}_7\left(s\right)+2NaB{O}_2\left(s\right)$

Colemanite on treating with sulphuric acid produces orthoboric acid but not borax.

Neutralising boric acid with soda ash gives borax. The following is the reaction:
$4H_{3}B{O}_3\left(s\right)+N{a}_{2}C{O}_3\to N{a}_2{B}_4{O}_7\left(s\right)+6H_2$