Question

In the borax bead test of $C{o}^{2+}$, the blue colour of bead is due to the formation of:

• A. $B_2{O}_3$
• B. ${Co}_3{B}_2$
• C. $Co{\left({BO}_2\right)}_2$
• D. $CoO$

Answer 1

The correct option is C $Co{\left({BO}_2\right)}_2$

On heating with a colored salt, the glassy bead forms a colored metaborate in an oxidizing flame.

The blue colour in the test of $C{o}^{2+}$ is due to cobalt metaborate ($Co(B{O}_2{)}_2$).

Hence, option C is correct.