Question

Select correct statement(s):
A.Borax is used as a buffer
B.1 M borax solution reacts with equal volume of 2 M ${\text{HCl}}$ solution
C.Titration of borax can be made using methyl orange as the indicator
D.Coloured beads obtained in borax-bead test contain metaborate.

Answer 1

Borax contains a weak acid and its conjugate salt. One mole of borax gives 2 moles of hydroxide ion. Methyl orange is generally used for the titration of acids.

Complete step by step answer:
Molecular formula of borax is ${\text{N}}{{\text{a}}_2}{{\text{H}}_4}{{\text{B}}_4}{{\text{O}}_9}$.
The IUPAC name of borax is sodium tetraborate.
Let's look at each of the statements given in regard to the Borax.
The aqua solution of borax acts as a buffer.
A buffer is a substance that resists change in pH. This means that when a small amount of acid or base is added to the buffer solution the pH does not change it remains the constant. because the extra bass acid is neutralized by the buffer solution.
Borax dissociates in water giving a weak acid that is boric acid and the conjugate salt that is sodium metaborate. The reaction occurs as follow:
${\text{N}}{{\text{a}}_2}{{\text{H}}_4}{{\text{B}}_4}{{\text{O}}_9} + {{\text{H}}_2}{\text{O}} \to 2{\text{Na}}\left[ {{\text{B}}{{\left( {{\text{OH}}} \right)}_4}} \right] + 2{{\text{H}}_3}{\text{B}}{{\text{O}}_3}$
Hence the borax acts as a buffer.
If you look at the above reaction of borax with water an acid and a salt is formed. The salt will dissociate and gives the $N{a^ + }\& {\left[ {B{{\left( {OH} \right)}_4}} \right]^ - }$ ions the ${\left[ {B{{\left( {OH} \right)}_4}} \right]^ - }$ will act as a base because of negative charge it can donate electron.
${\text{HCl}}$ is also an acid and hence it will not react with an acid. So the negative ion will react with ${\text{HCl}}$ and in the balance chemical equation 2 moles of anions are generated. So to moles of ${\text{HCl}}$ will be consumed. So 1 molar borax solution will react with 2 molar ${\text{HCl}}$ solutions with the same volume.
In borax bead test the borax is held at the hottest part of the flame with the help of a rod after sometime it is observed that the mixture swells and the borax loses all its water molecules and a mixture of sodium metaborate body can hydride is formed.
The titration of borax can be done using a methyl orange indicator. Methyl orange gives red color in an acid and yellow color in a base.

Hence all the statements are correct.

Note:
Borax is contained in detergent cosmetics. It is also used as an antifungal compound and as food additive, in flux, as a water softening agent and co-complexing agent.