Question

Borax bead test is used to identify the:

• A. Anion in metal salt
• B. Cation in metal salt
• C. Salt
• D. Metalloid

Answer 1

The correct option is B Cation in metal salt

Borax bead test is used to identify the metal cation such as $N{i}^{2+},C{o}^{2+},C{r}^{3+},C{u}^{2+},M{n}^{2+}$ etc.
Borax reacts with certain metal salts such as$N{i}^{2+},C{o}^{2+},C{r}^{3+},C{u}^{2+},M{n}^{2+}$ to form colored metaborates.

THEORY
Borax-bead Test:
Borax reacts with certain metal salts such as $N{i}^2+,C{o}^{2+},C{r}^{3+},Cu2+,Mn2+$ basically transition metal cations, etc., to form colored metaborates. $B{O}_2^{-}$ is known as metaborate. $B_2{O}_3$ is glassy transparent bead.
$Cr(B{O}_2{)}_2$ is green in colour while $Cu(B{O}_2{)}_2$ is blue in colour.
The colour of the metaborates can be used to identify the metallic ions (cations) in its salts.
$N{a}_2{B}_4{O}_7.10H_{2}O\stackrel{△}{\underset{-10H_{2}O}{\to }}N{a}_2{B}_4{O}_7\stackrel{{740}^{\circ }C}{\to }\underset{\text{Glassy mass}}{2NaB{O}_2+B_2{O}_3}$
$CuO+B_2{O}_3\to \underset{\text{Blue bead}}{Cu(B{O}_2{)}_2}$